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Saturday, December 31, 2011

My 1998 Chevy Cavalier Z24 2.4L Quad 4 LD9 Engine Performance Tuning Maintenance Repair Guide

My 1998 Chevy Cavalier Z24 2.4L Quad 4 LD9 Engine Performance Tuning Maintenance Repair Guide

This Is My 1998 Chevy Cavalier Z24 2.4L Quad 4 LD9 Engine Performance Tuning Maintenance Repair Guide. I'm Building This 1998 Chevy Cavalier Z24 2.4L Quad 4 LD9 Blog Guide To Keep Track Of My Notes As I Attempt To Repair My 1998 Chevy Cavalier Z24 2.4L Daily Driver With Odd Intermittent Issues.

Due To The Amount Of Issues My 1998 Chevy Cavalier Seems To Have On Any Given Day This 1998 Chevy Cavalier Z24 Blog Will Likely Become The Biggest 1998 Chevy Cavalier Z24 LD9 2.4L Engine And Car Maintenance, Repair, Performance Tuning, And Modification Guides On The Internet Some Day.

1998 Chevy Cavalier Z24 LD9 2.4L Engine Performance Tuning And Modification Guide Introduction. Learn First Hand What Enthusiastic Electronic Engineers, Auto Mechanics, And Machinists With The Knowledge, The Experience, The Right Tools For The Job, And $100,000 Canadian Cash Thrown At A 1998 Chevy Cavalier Z24 LD9 2.4L Engine And Car Can Do!

A Free Inside Out Everything You Need To Know To Do The Job Right All Compiled In One Nice Place Guide To Converting Your Current Stock High Mileage 1998 Chevy Cavalier Z24 LD9 2.4L Engine And Car You Know Absolutely Nothing About Into The Maximum Mean Machine It Can Be And You Knowing Exactly How Its All Working Under The Hood!

A Complete Rip Down, Review, And Reference Of The 1998 Chevy Cavalier Z24 LD9 2.4L Engine And Car Including The ECU CPU, RAM, ROM, EEPROM, And Flash ROMS, And All Components Installation, Diagnosis, Repair, Wiring Diagrams, Part Numbers, Technical Service Bulletins, And Did It Ourselves Hands On Estimate Labor Times So You Can Fix Your Own 1998 Chevy Cavalier Z24 LD9 2.4L Engine, Car, And Its Parts Yourself Or For As Cheap As Possible And Not Get Ripped Off By Another Incompetent Mechanic Shop Again!

Covers Absolutely Everything You Need To Know About Ripping Down, Diagnosing, Repairing, And Building Up A Stock Naturally Aspirated 1998 Chevy Cavalier Z24 LD9 2.4L Engine And Car Into A Super Charged 200HP+ Level 2 Daily Driver, A Turbo Charged 300HP Level 3 Street Legal Sports Car, A Twin Charged Level 4 400HP Quazy Street Legal Racing Car, And Triple And Quad Charged Level 5 500HP+ Street Illegal Racing Strip Only Race Cars That Hold Their Own And Always Turn Heads!

This 1998 Chevy Cavalier Z24 LD9 2.4L Engine Performance Tuning Guide Blog Site Is about modifying and tuning 1998 Chevy Cavalier Z24 LD9 2.4L Engines. This 1998 Chevy Cavalier Z24 LD9 Engine Performance Tuning Guide Blog site is strictly dedicated to building pimped out power house 1998 Chevy Cavalier Z24 LD9 2.4L Engines and custom 1998 Chevy Cavalier Z24 LD9 2.4L cars. 1998 Chevy Cavalier Z24 LD9 2.4L Engine Tuning, fast 1998 Chevy Cavalier Z24 LD9 2.4L modified street cars and even faster 1998 Chevy Cavalier Z24 LD9 2.4L modified race cars.

This 1998 Chevy Cavalier Z24 LD9 2.4L Engine Performance Tuning Guild Blog provides you with a complete, comprehensive, and in depth review of the 1998 Chevy Cavalier Z24 LD9 2.4L Engine and the 1998 Chevy Cavalier Z24 LD9 2.4L Car and all the LD9 engine specifications, diagrams, components, articles, exploded views, wiring diagrams, technical service bulletins, about modified cars.

1998 Chevy Cavalier Z24 LD9 2.4L Engine And Car customization and Car modifications that you will find educational, invaluable, and will take you a long, long way to helping you build really fast, long lasting, and durable 1998 Chevy Cavalier Z24 LD9 2.4L modified cars for legal daily driving street use or for race car and race track racing.

Our aim is to help inform and educate you about the 1998 Chevy Cavalier Z24 LD9 2.4L Engine, its potential and capabilities, and to generally guide and help you to modify your 1998 Chevy Cavalier Z24 LD9 2.4L Engine equip car, and its 1998 Chevy Cavalier Z24 LD9 2.4L engine to improve 1998 Chevy Cavalier Z24 LD9 2.4L Engine Performance and handling by providing you with all the information, tips and advice you would need to select the correct high performance auto parts for your car, to install them correctly, and to tune them.

It doesn't matter whether your car modification project entails building really cool custom cars, fast modified race cars, cool modified street cars, or even pimped out cars we will provide you with the information you would need.Information about engine tuning and car modification can become quite technical, but we attempt to bring you this information in plain English.

We make the information as easy to understand as possible so that even the novice can learn about car tuning and car modifications, as well as how to increase engine power. We also guide you through engine tuning, performance tuning and car modifications for all makes of cars, including BMW, Honda, Ford, Nissan, and much more, with detailed, step by step tuning and modifying tips.

And if you do get stuck with a technical term, there's always our glossary of modified car terms that you can checkup the term. If that doesn't help, you can always send us a message through our feedback form. We discuss various techniques of car customizing and various car modifications, as well as the different car tuning methods you can use to increase engine power, maximize car performance, and build great modified cars; including:

1998 Chevy Cavalier Z24 LD9 2.4L Engine Tuning. Learn about the basics behind car modification and engine tuning. Learn how to increase engine power and build engines for power and reliability. 1998 Chevy Cavalier Z24 LD9 2.4L Cylinder Head Porting Learn all about performance camshafts and cylinder head porting. Also learn about valve timing, camshaft timing and how to degree your camshaft. 1998 Chevy Cavalier Z24 LD9 2.4L Nitrous Injection Learn how to design wet and dry Nitrous Oxide Systems for your car. Also learn how to install NOS kits to your car and how to test and tune them.

1998 Chevy Cavalier Z24 LD9 2.4L Turbochargers Learn how to select and install the right turbocharger kit for your car. Also learn how to minimize turbo-lag and how best to tune a turbo or twin-turbo car.

1998 Chevy Cavalier Z24 LD9 2.4L Superchargers

Learn about the different types of superchargers and how to select and install the right type of supercharger that will give you the power you want. 1998 Chevy Cavalier Z24 LD9 2.4L Electronic Fuel Injection

Learn how to maintain, modify and tune electronic fuel injection (EFI), engine control unit (ECU) and engine management systems for the best performance.

1998 Chevy Cavalier Z24 LD9 2.4L Engine Management

1998 Chevy Cavalier Z24 LD9 2.4L Ignition Systems

Learn about the different ignition systems and how to improve and tune your ignition system for turbocharged, supercharged and modified engines.



1998 Chevy Cavalier Z24 LD9 2.4L Air Intake Systems

Learn how to improve air flow in and out of your engine by eliminating restrictions in the air intake system, and tuning the intake manifold and runners.

1998 Chevy Cavalier Z24 LD9 2.4L Exhaust Systems

Learn how to design and build performance exhaust systems with the correct primary pipe lengths and diameters for all types of high performance cars.



1998 Chevy Cavalier Z24 LD9 2.4L Suspension Tuning

Learn more about your car suspension and how to tune your suspension to be able to get the most out of your engine modifications.



We will be updating this Web site and adding more information on a regular basis so that it can serve as a complete resource on modified cars, custom cars and car modification. We hope that you find this Web site and its car modification guides informative and useful for building your own cool custom car, performance tuning your own car, and getting the best performance out of your car. All the information presented here has been thoroughly researched by our contributors. In our quest to provide the best source of information on car tuning and car modification, human error is always a possibility. Therefore, you should always consult your motor mechanic about your specific car before performing any car modifications to it, and always take the necessary safety precautions before tuning cars and engines! Should you find any errors on our Web site, please inform our webmaster so that we can correct them as soon as possible. You should also note that some car customizations, such as increasing your car's ride height, can adversely affect car performance and safety, while other car modifications may be illegal in your area. You should always ensure that your car customizations are legal. Feel free to use our feedback form to contact us if you have any queries about modified cars, car modifications, car tuning and car customizing in general. We do our best to respond to all queries. Alternatively, you could join our forum and post your queries there. If you want to customize a few cars and turn them into hot custom cars come visit soon for more information and guides to modifying cars as we will be updating our website with the latest information and tips on customizing cars and car modifications on a regular basis. We hope you enjoy your stay and trust that you will enjoy your car modification project even more! We look forward to seeing your modified car in the future!
How To Increase Engine Power And Performance

The Basics To Maximizing Engine Power The four stroke engine.

The 1998 Chevy Cavalier Z24 LD9 2.4L Engine Performance Tuning Guide Blog is all about 1998 Chevy Cavalier Z24 LD9 Engine Performance Tuning and 1998 Chevy Cavalier Z24 LD9 2.4L Car Performance And Modifications. So if you want to know about 1998 Chevy Cavalier Z24 LD9 2.4L engine and car tuning, how to increase 1998 Chevy Cavalier Z24 2.4L engine power and how to modify your 1998 Chevy Cavalier Z24 LD9 2.4L car, then the 1998 Chevy Cavalier Z24 LD9 2.4L Engine, Car, Tuning, Modification, and Maintenance guide is for you!

Before anyone can start talking smack about 1998 Chevy Cavalier Z24 LD9 2.4L engine tuning and increasing your 1998 Chevy Cavalier Z24 LD9 2.4L engine power and torque, they first need to have a basic understanding of how the 1998 Chevy Cavalier Z24 LD9 2.4L internal combustion engine produces power.

Therefore, over the next few pages of this section, we'll discuss the various basic concepts and principles of the internal combustion engines and the common terms used to discuss engine modifications, such as volumetric efficiency, engine displacement and air density as all of these influence engine power and performance. We also have a glossary of car modification terms that you can check for the meaning of some of the terms we use on this site. Once we have a clear understanding of how a four stroke engine produces power, we can move on and start make our P.L.A.N.s to increase engine performance.

Although there are two types of internal combustion engines, namely the two stroke engine and the four stroke engine, we're only interested in car performance and since the two-stroke engine is not used on cars, we won't be discussing that engine here. Instead we'll focus out attentions soely on the four-stroke engine because custom-car.us is all about car tuning and because cars use the four-stroke engine and not the two-stoke engine. If you're looking for information about the two-stroke engine, you could try How Stuff Works or Wikipedia. The Wankel rotary engine. There are also numerous derivatives of the four stroke engine – diesel engines, petrol engines, four cylinder engines, straight sixes, boxer engines, rotary or wankel engines, turbocharged engines, supercharged engines, etc. With the marked exception of the rotary engine, all four stroke engines have a common basic design – they all consist of individual cylinders with pistons that are connected to a flywheel by a crankshaft, and they all make use of what is known as the Otto Cycle. This makes it fairly easy to discuss basic engine power concepts as we don't need to concern ourselves with V's and straights, boxers and horizontally opposed engines. Instead our discussion can and will be all about the four stroke internal combustion engine. In addition, the deisle engine has had a resurgence in recent years and has become more of a performance engine, especially the turbo-diesel engine. A lot of what we discuss here can be applied to modern diesel engines but there are some aspects of engine modification that are specific to diesel engines; for this reason we'll discuss diesel engines and diesel engine modifications on their own. So let us begin by looking at the four strokes of the four stroke internal combustion engine otherwise known as the Otto cycle. You can skip this section if you're already familiar with the Otto cycle and head on over to basic engine power or engine building, but this section does tie into most of what we discuss on Custom-car.us. If you're intereseted in modifying diesel engines, hop on over to our page on diesel engines to find out how to apply our discussions to diesel engines. When you want to increase engine power on a four stroke engine, it is the efficiency of each stroke, particularly the intake and exhaust strokes, that you need to improve. Understanding the four stoke cycle of the internal combustion engine and how it produces power is important when you want to increase engine power. So let's begin with the four stroke cycle which is also known as the Otto cycle. If you're familiar with the four stokes of the Otto cycle feel free to head on over to power basics. Otherwise read on as this section is important to understanding engine tuning.

The intake stroke is the first stroke of the Otto cycle. During this stroke the intake valve opens as the piston moves from top dead center (TDC) to bottom dead center (BDC). The downward movement of the piston creates a vacuum in the cylinder that causes air/fuel mixture to be drawn into the cylinder. The intake valve usually opens slightly before the stroke begins and closes slightly after the stroke ends to maximize the amount of air/fuel mixture that can be drawn into the cylinder. The volume of air/fuel mixture that is drawn into the cylinder, relative to the volume of the cylinder, is called the Volumetric Efficiency (VE) of the engine. Maximizing the VE of the engine is an effective method of engine tuning that we can use to increase engine power, especially as stock engines generally have a VE in the range of 85% while older engines have a VE in the range of 70%. The compression stroke is the second stroke of the Otto cycle. Both the intake and exhaust valves are closed. The piston moves from BDC back up to TDC, forcing or compressing the air/fuel mixture into the combustion chamber of the cylinder head. The movement of the piston also causes turbulence which mixes the air/fuel mixture further, allowing more of the chemical energy in the fuel to be released during the power stroke. While it is the fuel that stores the chemical energy that drives the engine, it is the air that allows the fuel to burn and release its energy. Too little air leads to a rich fuel mixture that does not burn completely and does not release all the energy in the fuel, robbing the engine of power and economy. Too much air leads to a lean fuel mixture that burns too quickly. When the air/fuel mixture burns too quickly, it spends its energy too soon and creates too much pressure too quickly. This can cause irreparable damage to the engine. The chemically ideal ratio of air to fuel is 14,7 parts air to 1 part fuel (14,7:1) and is referred to as the stoichiometric condition. However, the air/fuel mixture requirements of the internal combustion engine are influenced by RPM, engine load and temperature. Heat is required for fuel vaporization. Therefore, in cold start conditions, a richer mixture is required and at full throttle, or wide-open-throttle (WOT), a leaner mixture is required. This is why fuel injection has a major advantage over the carburetor; it can provide the correct air/fuel mixture under varying conditions.

The power stroke is the next stroke in the Otto cycle and is also the start of the second revolution of the engine. The intake and compression strokes require a complete revolution of the engine, while the power stroke and the exhaust stroke require another revolution; in other words, the four stroke cycle is completed over two revolutions of the engine. Just before the start of the power stroke, the spark plug fires, igniting the air/fuel mixture which then burns in a controlled manner. This causes an increase in temperature and an expansion of the gasses in the combustion chamber, and ultimately increases the pressure in the combustion chamber. This pressure increases progressively and acts upon the top of the piston, pushing it down the bore to BDC. It is important to note that the pressure increases progressively until peak cylinder pressure is reached at approximately 12° to 14° after TDC. If peak pressure is reached at TDC, there would be too much pressure on the bearing and crankshaft, which would absorb a large amount of the power being produced. The pressure pushing down on the piston and forces the crankshaft to rotate, converting the chemical energy in the fuel to mechanical energy. Unfortunately, the internal combustion engine is not very efficient and a lot of this energy is lost through heat that is absorbed by the engine, and lost through the exhaust. Though the heat energy that is lost through the exhaust can be used to drive a turbocharger so it can't be all that bad, can it? The burnt air/fuel mixture is expelled from the engine during the exhaust stroke. The exhaust valve opens slightly before the stroke begins. With the exhaust valve open, the movement of the piston from BDC to TDC forces the burnt air/fuel mixture through the exhaust valve and out of the engine. Usually, the exhaust valve opens slightly before the stroke begins and closes slightly after the stroke ends, allowing the engine to expel as much burnt air/fuel mixture as possible. Any burnt air/fuel mixture or exhaust gasses that remain in the combustion chamber after the exhaust stroke will contaminate the fresh air/fuel mixture that in drawn into the cylinder on the next intake stroke, and will effectively reduce engine power. The intake and exhaust valves can open slightly before the start of their respective strokes and can close slightly after the end of their respective strokes because the linear movement of the piston slows down dramatically to a dead stop as it reaches TDC and BDC. However, the opening and closing of the valves must occur at exactly the correct moment to ensure maximum engine power, particularly as the fresh air/fuel mixture coming into the cylinder just before the end of the exhaust stroke helps push out more of the burnt air/fuel from the previous cycle through a process called "scavenging". We discuss valve timing in our section on camshafts and cylinder heads; but in our next section on engine basics, we'll look at how to increase engine power.

There are four ways in which you can increase engine power:

Increase the engine displacement by boring the motor out or stroking the crankshaft.

Increase the engine speed.

Improve the Volumetric Efficiency of the engine.

Increase the air density.

Essentially, all these engine tuning methods seek to improve air flow in and out the engine.

DISPLACEMENT

Engine capacity or displacement is measured by the formula (π/4 × bore2) × stroke × cylinders. The bore is the diameter of the cylinder; thus (π/4 × bore2) gives us the area of the cylinder. The stroke is the distance the piston travels from TDC to BDC and gives us the length of the cylinder. Multiplying these two measurements gives us the volume of one cylinder. Multiplying the volume of each cylinder by the number of cylinders that engine has will give us the total displacement of the engine. Thus, by increasing the area, length, or number of cylinders, we can increase the displacement of the engine. Unfortunately we can't increase the number of cylinders so we're left with the area and the length. We can increase the cylinder area by boring the motor. This is the easiest way of increasing displacement, but is restricted by the thickness of the cylinder walls, and the space between the cylinders. We can also increaser the length by stroking the crankshaft. This is more complicated as it requires the offset machining of the big-end journals on the crankshaft and possibly on the conrods. If the big-end journals of the conrod cannot be ground, you must either find slightly longer conrods that will fit, or pistons with a shorter compression height, i.e., the distance between the center of the gudgeon pin and the piston top. Stroking is restricted by the clearance between the rotational diameter of the crankshaft and the engine block.

ENGINE SPEED

Increasing engine speed does not increase the power per cycle, but increases the rate at which power in produced as the number of cycles per time frame increase. In other words, power is being produced more often as the Otto cycle is being completed much quicker. Increasing engine speed above the red line of the stock engine generally requires a complete engine rebuild with forged pistons, stainless steel conrods, stainless steel crankshaft, and a more robust valve train.

VOLUMETRIC EFFICIENCY

The Volumetric Efficiency (VE) of an engine is the amount of air/fuel mixture that is ingested by the engine during the intake stroke, relative to the engine’s displacement. There are a number of factors that prevent a stock engine from achieving a 100% VE. Chief among these are restrictions in the airflow path of the intake and exhaust, valve overlap effects, and reversion. Restrictions in the airflow on the intake side include the air filter, the throttle body, the plenum and runners, and the intake port. These restrictions can be overcome to some degree by fitting a high-flow air filter, and improving air flow through porting and gas flowing, especially on the cylinder head. Restrictions on the exhaust system include the exhaust header, the catalyst converter, and the mufflers. Unfortunately, anti-emission legislation requires that the catalyst converter be retained on street legal cars but restrictions in other areas of the exhaust system can be overcome by fitting a free flow exhaust header and free flow exhaust mufflers. Fitting a free flow exhaust system will also reduce reversion, which is the flow of exhaust gasses back into the combustion chamber. Reversion causes contamination of the air/fuel mixture and takes up space that the air/fuel mixture should fill, thus reducing volumetric efficiency. Too much back pressure in the exhaust system will cause reversion. As Bre suggests in our exhaust guide, fitting a free flow exhaust header that is slightly larger than the exhaust port on the cylinder head reduce reversion but an anti-reversion (AR) header that is specially designed to inhibit reversion would be even better.

AIR DENSITY

Denser air produces more power because it has more air molecules per volume. There are two ways in which air density can be increased – by lowering the air temperature, or increasing air pressure. Unfortunately, we can't really lower the air temperature but we can increase air pressure. The easiest way to increase air pressure would be to drive at lower altitude but this isn't really practical. The other way is to use forced induction. The three forms of forced induction are:

Installing a supercharger.

Installing a turbocharger.

Installing Nitrous injection.

Bre doesn't believe NOS is forced induction, but that's his problem. Forced induction is the easiest ways of improving engine power and if done correctly, you can easily increase power by up to 50%! Now that's major engine power!

Engine Building for Power and Reliability

If you're planning to do some serious modifications to a four stroke engine, you'd better do it right if you don't want to end up with an expensive pile of scrap metal. It's easy to slap on a turbo and run mild boost on a stock engine or even fitting a bigger turbo to an OEM turbo engine, but if you're looking for serious power, you have to rebuild the subassembly to ensure that it can handle the additional power without disintegrating. Obviously you need to ensure that your drive train can handle the extra engine power as well, but in this section we'll discuss engine building for maximum power, starting with the subassembly.

THE CYLINDER BLOCK

You've got to start by ensuring that your cylinder block is race grade. Even if you're just building a street race car, engine tuning would be senseless if the block is not up to the job. Start by pressure testing the block. If you have an air compressor you can do this yourself. Strip down the engine but leave the Welch plugs and oil gallery plugs in place. Fit the bare cylinder head to the cylinder block using new head gasket or one that's not too worn. Close all water opening off with steel plates. One of the plates must be fitted with an air line fitting that you can connect your air compressor to. Gradually increase the pressure in the block to 40 psi. Don't increase the pressure too quickly as a loose fitting Welch plug or a weak spot in the block could blow out can cause you serious injury. If everything is still in place, gradually increase the pressure to 50 psi. Now spray the block with a mild water/detergent mixture. Carefully check the block for air bubbles. If you see bubbles, either have it repaired or test another block. If you get no bubbles, release the air pressure and remove the cylinder head. Use a plug tap to clean the head stud and main bearing cap threads and chamfer any stud hole that is not already chamfered. This will prevent the thread from pulling up. Grind away any casting sag, especially around the main bearing webs, the sump pan deck, and the valley area of a Vee engine. This will prevent cracks from developing. Now remove all the Welch plugs and oil gallery plugs and have the block boiled and cleaned in a chemical bath. This will remove all rust and scale in the water channels, and the caked oil in the oil galleries.

THE CRANKSHAFT & CON RODS

Chrome-moly forged con rods The stock crankshaft and con rods are usually cast iron items that can be retained if the engine is not required to handle high boost pressures, high horse power, and high revs. Forged crankshafts and con rods are much stronger and are more suitable for high load, high rev engines. In either event, you should have the crankshaft and con rods Magnafluxed to check for cracks.

If the crankshaft has no cracks, check it for straightness. A crankshaft that is even 0.002in out of straight will increase bearing load and will be the cause of bearing failure. If your crankshaft is out of straight, you have two options – either have the crankshaft straightened or machine the crankshaft's main journals so that crankshaft rotation is true. However, straightening a crankshaft that is to be used for a high boost, high horse power, and high rev engine is a waste of time and money as the combustion pressure and inertia loads will reverse the straightening process. Machining the crankshaft journals will also weaken the crankshaft. Ultimately, replacing a bent crankshaft is your best option.

It goes without saying that all the crankshaft journals should be checked for roundness and size. The same goes for the big end on the con rods. The crankshaft, con rods, and flywheel should then be balanced statically and dynamically to reduce shock loading and vibration.

THE PISTONS

High strength forged pistons The next thing you need to consider is the pistons. Most OEM engines are fitted with cast aluminum pistons with a slotted oil groove. High performance OEM engines may be fitted with hypereutectic cast aluminum pistons that have a higher silicon content. The higher silicon content makes the cast material much harder and more wear resistant, which allows these pistons to withstand greater temperature and pressure loads. This makes these pistons ideal for street racers. However, the higher silicon content also makes the pistons more brittle and prone to breaking under detonation. Thus, these pistons are not a good choice for forced induction applications where the possibility of detonation in greatly increased.

Forged pistons, on the other hand, have much denser and even harder than hypereutectic cast aluminum pistons but are not as prone to breaking under detonation. Forged pistons also have drilled oil holes round the oil groove rather than a slot in the oil groove. This makes them the best option for high horse power, forced induction engines.

Pistons can also be either full skirt pistons or slipper type. The full skirt pistons are heavier but stronger and less prone to wobble. Needless to say, they would be the best option for any engine modification project.

The Diesel Engine

The diesel engine was developed by Rudolf Diesel and was patented in 1892. Diesel engines are very similar to petrol or gasoline engines in that both rely on the Otto cycle to convert the chemical energy in fuel into mechanical energy and, in so doing, produce power. The major difference is the way fuel is delivered to the combustion chamber and the way the fuel mixture is ignited. Firstly, in gasoline engines, the fuel is usually fed into the intake manifold or the intake port where it is combined and mixed with the intake air, which is also called the intake charge. In modern diesel engines, the fuel is injected directly into the combustion chamber. This means that only the intake charge is compressed during the compression stroke and the diesel is only introduced once the intake charge has been compressed. Secondly, in gasoline engines, the fuel mixture is ignited by a sparkplug, while in diesel engines the fuel is ignited by the heat from the compressed air in the combustion chamber. However, diesel requires a much higher temperature than petrol before ignition (not spontaneous ignition) can take place.

These differences has important consequences for the modification of diesel engines, especially when you consider the differences between diesel fuel and gasoline.

THE DIFFERENCES BETWEEN DIESEL AND GASOLINE

For starters, diesel is a heavier fuel than gasoline. In other words, it contains more carbon atoms in longer chains than gasoline (technically, gasoline is typically C9H20, while diesel fuel is typically C14H30). Because it is heavier, diesel is much more stable that gasoline and vaporizes at a much higher temperature than gasoline. It also vaporizes much slower than gasoline and burns much slower. The result is that diesel requires a much higher temperature to ignite. Gasoline, for example can burn at temperatures of -40° F while diesel requires a temperature of at least 143° F! The main point, however, is that diesel burns slower than petrol. This means that it will produce a steady pressure on the piston for longer. Consequently, diesel can be ignited at a higher temperature, and indeed can be allowed to reach the point at which it will ignite spontaneously. The interesting thing is that diesel needs a temperature of 410° F to ignite spontaneously but will ignite or burn at a much lower temperature of 143° F. Consequently, diesel cannot be introduced into the combustion chamber until the correct temperature is reached, or else it will pre-ignite. Now, to reach the required temperature, air in the combustion chamber must be compressed much more than in a gasoline engine, and because there is not fuel in the combustion chamber, the intake charge can be safely compressed without the danger of pre-ignition. Thus a gasoline engine will typically have the compressions ratio would of somewhere between 1:9 and 1:12 while a diesel engine will typically a compression ratio of around 1:25! And it is this higher compression ratio, as well as its higher vaporization point and slower burning rate and the fact that diesel has about 17% more energy density than gasoline, that makes diesel much more efficient than gasoline.

Now you're thinking why not use direct injection in a gasoline engine so we can increase the compress without pre-ignition? Indeed some manufacturers to employ direct injection on gasoline engines, but without the higher compression ratio because gasoline will burn too quickly at higher temperatures, hence the need to keep the temperature of the intake charge down in a gasoline engine. Remember, diesel burns at a slower rate than gasoline and therefore can be ignited at higher temperatures.

DIESEL ENGINE MODIFICATIONS

When it comes to modifying a diesel engine, you can apply the same techniques that you would apply to a gasoline engine, except for ignition system obviously as diesel engine has no spark plug. All the basics apply, i.e., increasing the engine displacement, increasing the engine speed, improving and increasing the air intake, and increasing the volumetric efficiency. Nonetheless, there are a number of things to consider before attempting to modify a diesel engine. Firstly, components in the diesel engine are exposed to far higher pressures and temperatures than the components in gasoline engines. Therefore, diesel engines need to be more robust with thicker cylinder walls and stronger pistons. Should you decide to increase the displacement of your diesel engine by boring out the cylinders you should ensure that you improve your cooling system. Secondly, diesel burns at a much slower rate than gasoline; therefore a diesel engine will operate at a much lower RPM. This is natural, and getting the diesel engine to operate at higher speed will mean increasing the temperatures in the combustion chamber, which would require thicker cylinder wall and much a better cool system, and improving the cooling system is easier said than done because of diminishing returns!

Furthermore, increasing the temperatures in the combustion chamber will increase the heat in the intake manifold, and will result in a reduction of air density. Consequently, we're dealing with even more diminishing returns! Still, maximum power will be reached at relatively low RPMs because of the slow rate at which diesel burns and will drop off dramatically at higher RPMs.

Thirdly, increasing the amount of air ingested by the engine will require a proportionate increase in the amount of fuel injected into the engine. Thus bigger injectors, a higher fuel pressure will be required, or a remapped engine control unit (ECU) would be required. On some turbo-diesel engines, a remapped ECU has led to impressive improvements in power and should be the starting point in your quest to squeeze more power from a diesel engine.



1998 Chevy Cavalier Z24 LD9 2.4L Cylinder Head Modifying.

1998 Chevy Cavalier Z24 LD9 2.4L Cylinder Head Porting

Doing The Head

A Twin Cam Cylinder Head When it comes to getting the most power out of a naturally aspirated engine the key area that you must focus your attention on is the cylinder head. This is the one area that will potentially give you the greatest increase in engine power. Why? Well, as Langer explains in engine building and power basics, the key to increasing an engines horse power is to get the engine to ingest more air and be able to expel the resultant increase in exhaust gasses, in other words, getting the engine to pump more air by increasing the air-flow in and out of the engine. On a motor car engine, there are three areas that can affect air-flow and where you can make improvements. These are:

The intake system, which includes the air filter, plenum and the intake runners.

The exhaust system, which includes the exhaust header, catalyst converter and the mufflers.

The cylinder head, which includes the cylinder head ports, valve area and the camshafts.

We've discussed the intake system and the exhaust system elsewhere on this web site so now it's time for us to turn our attention to modifying the cylinder head. However, in this section we're going to discuss a little bit more than just the cylinder head, we're going to discuss cylinder head porting, gas flowing and power tuning the cylinder head, old school style! We'll also be discussing performance camshafts, cam timing, valve timing and valve overlap. A word of warning though, cylinder head porting and gas flowing is a rather advanced form of car modification and is not for the novice or for the faint of heart. Cylinder head porting is a skill that must be developed and honed by hours and hours of practice. If you're intent on trying cylinder head porting, the first thing that you need to know is the porting always begins by trial and error so if you're going to do your own cylinder head porting, start on a cylinder head that you can afford to total, in fact, start with a couple that you don't mind loosing. Otherwise you should leave cylinder head porting up to a professional with a flow bench. The other thing to note, is that cylinder head porting requires some rather expensive tools. You'll need a high-speed extended pneumatic die-grinder with carbide and steel grinders, and a high-pressure air compressor (no, we're not talking about turbochargers here) to power the grinder. You could use an electric die-grinder rather than a die-grinder, but electric die-grinders don't operate at a high-speed like pneumatic die-grinders. You could also use an electic drill rather than a die-grinder but you won't get the same results as you would with a longer, more agile and thinner die-grinder. An electric drill also does not operate at the high-speeds that a pneumatic die-grinder does. A Pneumatic Die Grinder Right, if you've read all that, bought your air compressor and your die-grinder, and gotten hold of a few spare cylinder heads, despite our warnings, then we can move on and start modifying the cylinder head for extreme power. But remember that we did warn you. Right, we'll begin by looking at the camshaft before moving on to the equipment you'll require to port your cylinder head, the basics of gas flowing and cylinder head porting itself.

Performance Camshafts

The two important aspects of a camshaft, in terms of engine performance, are camshaft duration, or cam duration, and valve lift. Both cam duration and valve lift are determined by the camshaft lobe. Cam duration is the time that at least one valve of a cylinder remains open, i.e., off its valve seat, measured in degrees rotation of the crankshaft, while valve lift is the maximum distance the valve head travels from the valve seat.

VALVE LIFT

Valve lift is somewhat related to intake valve head diameter. An engine with an intake valve head diameter of 1.400in to 1.500in will generally perform best with a valve lift of 0.395in to 0.475in; an engine with a larger intake valve head diameter of 1.750in to 1.875in will generally perform best with a valve lift of 0.425in to 0.550in; and an engine with a large intake valve head diameter of 2.000in to 2.250in will generally perform best with a valve lift of 0.475in to 0.650in. But these are just rough guidelines; ultimately you will need to take some gas flow readings on a flow bench to determine the best valve lift for your particular engine. A number of factors influence valve lift. The most important being the gap between the intake and exhaust valves, the piston to valve clearance and the intake charge pressure. These factors also influence cam duration. Another factor influencing valve lift is valve spring compression. Obviously, once the valve springs are fully compressed, it cannot give any more and the valve cannot be pushed further down into the combustion chamber.

CAM DURATION

As I've mentioned earlier, cam duration is measured in degrees rotation of the crankshaft, rather than the camshaft, and the crankshaft completes two full rotations for every rotation of the camshaft. In other words, with a 310 degree camshaft, the valves are open for only 155 degrees of actual camshaft rotation. A performance camshaft for a naturally aspirated engine will have a duration in the range of 270 degrees to 310 degrees or more, with a 270 degree camshaft described as a 'mild' camshaft and a 310 or more degree camshaft being described as a 'wild' race camshaft. A stock camshaft usually has a duration of around 270 degrees but what differentiates a 270 degree performance camshaft from a stock camshaft is increased valve lift and a much faster rate of valve lift. With a faster valve lift rate, the valve reaches full lift quicker and remains at full lift for longer. This increases Volumetric Efficiency (VE) as more air flow in and out of the engine is possible. A determining factor, when choosing camshaft duration is the purpose of the vehicle. The longer the duration of the camshaft, the further up the rev range the power band shifts, and the rougher the idle. Obviously, as the power band moves higher up the rev range, bottom end power is lost. Also, as cam duration and valve overlap increases, torque is lost. Fuel efficiency also decreases and exhaust emissions increase as valve overlap increases.

High performance camshafts start at 280 degrees of duration. These camshafts have increased valve overlap but not too much so emissions and fuel economy are not severely affected. These are generally good camshafts for modified street cars and produce good power from 2,500 RPM up to 7,000 RPM but they do not have a smooth idle because of the increased valve overlap. A 290 degree camshaft requires more cylinder head work in terms of cylinder head porting and gas flowing as they work better when the engine's Volumetric Efficiency (VE) is improved. As you'd expect, these camshafts produce a fairly rough idle. These camshafts are generally good for rally cars and produce power from 3,000 RPM up to 7,500 RPM. A 300 degree camshaft requires even higher levels of VE, reaching the physical gas flowing limitations of a two valve cylinder head with a single camshaft. These camshafts are good for modified race cars and produce good power from 4,000 RPM up to 8,000 RPM. However, they have a very rough idle. A camshaft with a duration of more than 300 degrees is an out and out race camshaft with a power band in the 4,500 RPM to 9,000 RPM rev range. To make effective use of a 300 degree camshaft, you need to ensure that the engine has a very high VE. You also need to ensure that the engine can rev beyond the red line of most stock engines.

VALVE OVERLAP

The limit for opening the exhaust valve is approximately 80° before bottom dead center (BBDC). Opening the exhaust valve any sooner tends not to increase power production but will shift the power band higher up the rev range and will reduce low end torque as downward pressure on the piston during the power stroke is released. The same applies to closing the intake valve where 80° after bottom dead center (ABDC) is the limit for increased power production.

Basic Cylinder Head Porting

Although it sounds quite complicated, gas flowing and cylinder head porting are actually quite simple. The main aim of both gas flowing and cylinder head porting is to improve the air-flow through the cylinder head. Understanding what is good for improving air-flow, and what is bad for air low, i.e., what restricts air-flow, will go a long way to making good power gains from your cylinder head porting and gas flow work, so let’s begin there.

AIR-FLOW

As "Bad Ass" Bre and "Langer" have mentioned else on this site, the key to engine power and car performance is good air-flow in and out of the engine. Getting more air/fuel mixture into the engine and getting the exhaust gas out efficiently after combustion will get you more power. This is what is called Volumetric Efficiency (VE).

In technical terms, Volumetric Efficiency is the ratio of the volume of fresh air/fuel mixture that is drawn into the cylinder on the intake stroke, relative to the swept volume of the cylinder. Obviously, any exhaust gas that remains in the cylinder after the exhaust stroke will occupy some of the volume that fresh air/fuel mixture should occupy, and would reduce the Volumetric Efficiency of the engine. Thus, how well the exhaust gasses flow out the exhaust system is also important. Generally speaking, a multi-valve cylinder head will have a better Volumetric Efficiency, and hence will create better power, than a two-valve cylinder head. So if you have the option of fitting a two-valve cylinder head, or a multi-valve cylinder head, I’d go with the multi-valve cylinder head.

IMPROVING AIR-FLOW

Improving the Volumetric Efficiency of your engine requires that you improve the air-flow in and out of the engine. Fortunately, there are a number of things that you can do to improve air-flow, particularly through the cylinder head. The first is to ensure that nothing obstructs or restricts the air flow to and through the cylinder head, from the moment air enters the intake system until the moment it exits out of the tail pipe. However, certain obstructions in the cylinder head ports, such as the valve stem and the valve guide boss, cannot be eliminated completely but can be minimized by narrowing the valve stem without weakening it too much and shaping the valve guide boss into a ramp.

Another way of improving air flow through the cylinder head is to form the cylinder head ports and the combustion chamber into an even, smooth and consistent shape. The key word here is consistency; constituency not only in shape and size, but also consistency from one cylinder to the other. You can achieve consistency in shape by ensuring that there are no intrusions or cavities in the port, and that the port does not widen or narrow. Air-flow can be further optimized by eliminating sharp turns and bends in the path of the air-flow.

ENLARGING THE PORT

Enlarging the cylinder head port might be a good way of improving air-flow, but it has a major effect on mean gas velocity. A small port, relative to the cylinder, will have a high mean gas velocity at low RPM but it will struggle to fill the cylinder at high RPM. Thus Volumetric Efficiency will tail off at high RPM and power will fall off quickly. Conversely, a relatively large port will have a low mean gas velocity at low RPM. To maintain fuel atomization, i.e., to keep the fuel droplets suspended in the air flow, a high mean gas velocity is required. If the mean gas velocity is too low, gravity will pull the fuel droplets out of the air stream and will form puddles of fuel on the port floor. The result will be a loss of power and economy.

Cylinder Head Portingby Double H (January 23, 2008)

Now that we've got a good understanding of air-flow, we can move on to cylinder head porting. If you haven't yet read our article on the basics of cylinder head porting and air-flow, I'd suggest you do so now as it provides the foundation for understanding what we want to achieve with the actual cylinder head porting.

PREPARING THE CYLINDER HEAD

Before we can get started, we need to strip down the cylinder head; remove the camshafts and camshaft pedestals, then remove the valves, valve springs and valve stem seals. You should also remove all manifold studs. With everything stripped, you need to inspect the cylinder head for cracks. It's no good porting a cracked cylinder head, though a cracked cylinder head may still be good for experimenting on, so don't throw it away! The most likely areas where cracks will appear are between adjacent valve seats, and around the valve seats, especially around the exhaust valve seats. You may need to some emery cloth to remove any carbon deposits to do a thorough check.

If you don't see any cracks, have the cylinder head thoroughly cleaned in a chemical bath. You can dip a cast iron cylinder head in a hot caustic solution but don't dip an aluminum cylinder head in it! Caustic solution will react with the aluminum and give off an explosive gas! For an aluminum cylinder head you should use Trichloroethane. If you don't have access to a chemical bath, you can use engine cleaner and a stiff brush to get oil and gasket pieces off. Once the cylinder head is clean and dry, use a sand blaster or a wire brush to clean off any stubborn carbon deposits. Once that's done, do another thorough check for cracks.

If you don't see any cracks, have the valve seats replaced and the valve guides removed by a reputable engineering shop. Replacing the valve seats are not crucial as long as they're in a good condition. However, you must have the valve guides removed.

WARNING: Take care when working with a grinder. Adhere to the following safety precautions when porting cylinder heads and using a grinder in general:

Wear eye protection when working with a grinder; goggles are advisable but a full face visor would be better.

Wear a dust mask or a respirator; inhaling metal filings is harmful.

PORTING THE CYLINDER HEAD

We'll get to enlarging the port in a while when we discuss gas flowing; but for now we'll focus on the main aim of cylinder head porting, which is to smooth and straighten out the ports. If this is your first attempt at cylinder head porting, I'd suggest you try to master that first. Starting on the intake ports, use a flame-shaped carbide and attempt to remove any obvious bumps and crevices in the port without removing too much metal, then try to straighten the post so that it has a consistent size from the mouth to the point where it curves into the valve throat. Remember to move the carbide all the time and don't hold it on one spot as it will quickly create a hollow that will be difficult to remove! Once you're happy that you've got your first port nice and straight you can use a grinding stone to smooth it if it's a cast iron cylinder head, or a sander band if it's an aluminum cylinder head. Now try to replicate your work on the other ports. Use an inside caliper to make sure all the ports are the same size. Now, working from the valve throat side, use an oval carbide to blend the short side radius. Again, try not to remove too much metal. Also remember that you want a smooth flow through the valve throat area and that you want a consistent port size through the length of the port. Once you have blended the short side radius, turn you attention to the long side radius where the valve guide boss is located. Use an oval carbide to flatten the valve guide boss until you have a consistent port size from the manifold face to the valve seat.

Now all that's left is to smooth the port with a flapwheel or a fan grinder; then use a vernier caliper to measure the height of the valve guide boss through the hole for the valve guide. Measure the height of the valve guide boss on its shortest side and on its longest side. Then replicate your porting work on the other ports until all the ports are identical. Once you're happy with the intake ports, turn your attention to the exhaust ports and smooth and straighten them out in the same manner, without removing too much metal and retaining the squarish shape of the exhaust ports.

MATCHING THE MANIFOLD

The intake manifold and exhaust header are integral to the efficient air-flow in and out of the engine. Getting a smooth flow from the manifold to the cylinder head ports, especially in the case of the intake manifold, is crucial for good air flow and power. Remember that air-flow doesn't like sudden changes in direction or tube size. As "Bad Ass" Bre mentioned in designing and building performance exhaust systems, the exhaust port can be slightly smaller that he exhaust header to help prevent reversion. Start by making a cardboard template of the intake and exhaust manifold faces, and cut out the port openings and the stud holes accurately. Fit the template to the cylinder head, taking care to match the cylinder head side of the template to the cylinder head. You will have to insert the manifold studs or manifold bolts into the cylinder head to line the template up correctly. Once the template is lined up accurately, scribe the outline of the template onto the cylinder head. You can also use a manifold gasket to mask out the port sizes if the port openings on the gasket fit the manifold accurately. Now you can enlarge the ports gradually until the intake port matches the port openings on the intake manifold, and the exhaust port is slightly smaller than the port openings on the exhaust header. Remember that the aim of cylinder head porting is to create a smooth straight port that has a consistent port size from the manifold face through the valve throat area. Also try to keep the ports walls on rectangular exhaust ports as straight as possible. You can use an engineer's square to scribe straight lines that can serve as guides for your porting on the port walls.

Valves and the Valve Train

Proper attention to the valves and valve train components is important when modifying a cylinder head. In fact, the cylinder head porting we discussed previously would be less effective if we do not improve the air-flow round the valves. That is what we'll be looking at in this section. We'll also be looking at fitting larger valves, improving air-flow round the valve guide, and improving the valve train components. We've already discussed the camshafts and valve timing elsewhere so we won't be repeating that here.

THE VALVES

The first thing to do with the valves is to check them for wear. If you find any signs of wear, then you need to replace the valve. You need to check both the valve stem, and the valve face. You can check the valve stem using a micrometer, or you can gently run your index finger and thumb along the length of the valve stem and work your way right round the stem. You can visually check the valve face for wear. If you feel the slightest ridge on the valve stem or the valve face is badly pitted, replace the valves. Most stock intake valves are made of EN52 steel while most stock exhaust valves are made of more wear resistant and stronger 21/4N Austenitic stainless steel. If you're building a modified street car, the stock valve material will be perfect, as long as the exhaust valves are made of 1/4N Austenitic stainless steel; however, if you're building a modified race car, it would be better to replace the stock intake valves with stainless steel valves, which are more wear resistant. As for the exhaust valves, you can easily verify whether they are made of 21/4N Austenitic stainless steel or EN52 steel as 21/4N Austenitic stainless steel is non-magnetic while EN52 steel is magnetic. So, if a magnet sticks to your exhaust valve head, it's EN52 steel. Some manufacturers use a bi-metal construction, with an EN52 steel valve stem micro welded to a 21/4N Austenitic stainless steel valve head; so check the valve head, not the valve stem.

FITTING LARGER VALVES

There are several things you need to take into account when deciding on bigger valves. The most obvious is that you need sufficient space in the combustion chamber for bigger valves. However, the valve head should be at least 2 mm from the combustion chamber and cylinder wall. Also, if you fit bigger valves, you'll need to open up the ports, which means you'll need to do more cylinder head porting to achieve the full power benefit of fitting bigger valves. But this also means that you'll have reduced the mean gas velocity at low RPM as bigger ports have lower mean gas velocity at low RPM. This translates into less bottom end power, especially on small bore engines. It's not necessary to fit bigger exhaust valves on a naturally aspirated engine, even if it's on a heavily modified race car. This is because of the large pressure differential in the cylinder and the exhaust header. The pressure in the cylinder during the exhaust stroke, when the exhaust valve opens is usually five times higher than the pressure in the exhaust header. Air flows from a high pressure area to a low pressure area until equilibrium is reached; therefore the exhaust gasses are literally sucked out of the cylinder. The movement of the exhaust gasses is aided by the upward movement of the piston, which keeps the pressure in the cylinder while forcing even more exhaust gasses out through the exhaust valve. This also explains why the intake valve is bigger than the exhaust valve.

Camshaft Timing

As with ignition timing, accurate valve timing, or cam timing as some people refer to it, is critical for achieving maximum horse power delivery from your engine. The first thing you need to accurately set your cam timing is a timing degree wheel, or a cam timing disc, that you can get from your camshaft manufacturer. You also need a dial gauge with a magnetic stand to find true top dead center (TDC) of the no. 1 cylinder and the correct valve lift, and an adjustable vernier gear. An adjustable vernier gear for accurate cam timing It is easiest to set the cam timing before the cylinder head is fitted to the engine. You need to accurately determine TDC using the dial gauge and accurately mark TDC on the crankshaft pulley. Usually, the car manufacturer would mark TDC on the crankshaft pulley, but you should verify that it is marked accurately as if it is even just a few degrees out, it can have a significant effect on power delivery. Accurately marking TDC on the crankshaft pulley will also be helpful when want to check or adjust the cam timing at a later stage, with the engine fully assembled and fitted. The next step is to bolt the cam timing degree wheel to the crankshaft, fit a temporary pointer to the engine block and set the pointer to TDC or 0° on the cam timing degree wheel. Then fit the cylinder head and install the camshaft, or camshafts if it's a twin-cam cylinder head. The engine should be at TDC and at the end of the compression stroke on the no. 1 cylinder, so the camshafts should be installed with the intake and exhaust valves of the no. 1 cylinder closed. The camshaft manufacturer or grinder will provide you with a specified valve lift and the point at which that valve lift for the intake valves and the exhaust valves should be achieved. This may be for full-lift, or a specified amount of valve lift with the valve opening. Also, the point at which the valve lift is achieved is measured in degrees of crankshaft rotation, which is why we bolted the timing degree wheel to the crankshaft. Our next step is to attach the dial gauge to the cylinder head, with the stylus on the intake valve of the no. 1 cylinder and zero the dial gauge. Now rotate the crankshaft to the specified point at which the specified valve lift should be achieved and read the amount of valve lift off the dial gauge. If it is not the same as the valve lift specified by the manufacturer, then free up the vernier gear and turn the camshaft until the correct valve height is achieved. Take care not to let the valves hit the crown of the piston while you're doing this adjustment as the valves could bend quite easily. With the specified valve lift of the intake valve occurring at the specified degrees of crankshaft rotation, tighten up the vernier gear. Your intake valve timing is now set. On a single-cam cylinder head you just need to verify that the exhaust valve also reaches the specified valve lift at the specified point. But on a twin-cam cylinder head you will need to set your exhaust valve timing by repeat this process for the exhaust valve of the no. 1 cylinder. It's quite easy in theory, but a bit more complicated if you need to determine the exact point that full-lift is achieved and the same applies to determining TDC accurately.

FINDING TDC

Finding TDC accurately is a bit complicated as the piston is stationary at its apex for a few degrees of crankshaft rotation. Thus assuming that TDC has been reached when the piston is at its apex is not accurate enough when you want to set cam timing. This is where the dial gauge and the timing degree wheel come in quite handily. Bolt the degree wheel to the crankshaft, fit a temporary pointer to the engine and place the dial gauge on the engine block with the stylus the no. 1 piston. Determine when the piston is at its apex and zero the dial gauge. Now rotate the crankshaft until the piston is a short distance, say ¼ inch or 5 mm, below its apex. Mark this point on the degree wheel. Now turn the crankshaft in the opposite direction until the piston is at the same distance below its apex and mark this point on the degree wheel. True TDC would be the mid-point between the two marks on the degree wheel.

FINDING FULL VALVE LIFT

The same technique can be used to determine when the camshaft reaches full valve lift. The toe of the camshaft lobe is shaped to keep the valves at full lift for as long as possible, which is usually a good number of degrees. If you need to find full lift as your reference point when setting your cam timing, you need to find the exact point of full valve lift. Start with the engine at TDC. Then turn the crankshaft back until the camshaft lobe acting on the intake valve of the no. 1 cylinder is pointing more or less upward and the intake valve is fully closed. Set up the dial gauge with the stylus on the valve retainer cap of the intake valve and zero the dial gauge. Now rotate the crankshaft until the intake valve opens and is a short distance, say 0.1 inch or 0.25 mm, past full lift. Mark this point on the degree wheel. Then turn the crankshaft in the opposite direction and stop when the intake valve starts to close and is at the same distance from full lift. Mark this point on the degree wheel. Needless to say, the point of full lift for the intake valve would be the mid-point between the two marks on the degree wheel. Now you just need to repeat this process to find the point of full lift for the exhaust valve.

Nitrous Oxide And NOS Kits

An Introduction to Nitrous Oxide (N2O) Injection

Nitrous Oxide (N2O), or NOS as it is commonly referred to, is a quick and easy performance boost for any motor vehicle, regardless of whether it's a car, a bike, a boat or a plane. In technical terms, Nitrous Oxide is a chemical compound that consists of two Nitrogen atoms and one Oxygen atom. However, Nitrous Oxide does not occur naturally as a chemical compound but has to manufactured by applying heat and a catalyst to nitrogen and oxygen compunds. Nitrous Oxide was first discovered by the British chemist, Joseph Priestly, in 1772 but it wasn't until 1942 that Nitors Oxide was first injected inon an internal combustion engine to boost the power output from the engine. Nitrous Oxide is not combustible and is in liquid form when under pressure. When it is released into the combustion chamber the pressure is removed and the Nitrous Oxide becomes gaseous, releasing extra Oxygen that allows your engine to burn more fuel during the combustion process. At the same time, the chemical process of changing from a liquid into a gas absorbs lots of the heat from inside the combustion chamber, reducing the chances of detonation and pre-ignition. NOS thus provides an instant but relatively safe performance boost. The major advantage of NOS is that it is relatively cheap when compared to all the other forms of car modification and the amount of work involved to install a full nitrous system is far less than that of installing high performance cam shafts, turbochargers or superchargers. The only drawback is that you must refill your Nitrous Oxide tank. Nitrous Oxide is stored in a pressurized tank to keep it in a liquid state. Unfortunately, Nitrous Oxide refills are not as freely unavailable as gasoline and must be purchased from an authorized dealer. The relative low cost of installing a NOS system makes it an ideal power boost project for anyone who can read and understand a little simple physics. As with anything in life, if you don't do it right, you're going to get problems. There is also more to installing NOS than just bolting a NOS tank to your trunk and connecting a long tube to your engine. The bottle has to be mounted at a 15° angle to ensure that the last of the gas is used and none is wasted. The plumbing is also very intricate and can be very tricky to a first time NOS installer. None the less, in this custom-car.us NOS guide, we will explain the physics of nitrous oxide injection and show you how to install a NOS kit and how to test and tune NOS. There are three different types of nitrous oxide systems that you can implement:

The Dry System, which is the NOS system in which no fuel is sent to the intake charge outside the vehicle's normal means.

The Wet System, which is the NOS system in which fuel and nitrous oxide are supplied through a fogger and then sprayed through the throttle body.

The Direct Port System, which is a Wet System in which each engine cylinder has its own fogger.

We'll cover all of these over the next few pages. Now let us start with some NOS basics ...

WARNING: NOS causes an extreme increase in fuel combustion; therefore, any problem in your engine can turn out to be 10 times worse with nitrous installed!

The basic nitrous oxide injection system, or a NOS kit, is pretty straight forward and easy to grasp. It consists of a nitrous oxide tank, some tubing, a nitrous solenoid, a fuel solenoid and toggle switch, throttle position microswitch, jets, a nitrous fogger, a relay, nylon pipe, and a distribution block.

The nitrous tank is used to store Nitrous Oxide in a liquid form. The tank is actually a pressurized canister as Nitrous Oxide must be compressed to remain liquid at room temperature. Remember N2O reaches boiling point (i.e., it becomes gaseous) at -127° F and more Nitrous Oxide can be stored when it is in a liquid form. Approximately 850 psi of pressure is required to keep Nitrous Oxide liquid at room temperature and at sea level but the nitrous tank must be pressure tested and certified to withstand 1,800 psi. If the certification on your NOS tank is older than five years, your nitrous dealer will not refill it and you will have to have the tank pressure tested and recertified. The tank is mounted in the car's trunk and has a siphon tube that is connected to the release valve and extends to the bottom of the tank. The tank must be mounted at a 15° angle to ensure that the maximum amount of Nitrous Oxide can be released from the tank.

High pressure nylon or Teflon inner-lined braided-steel pipe is used to carry the Nitrous Oxide to the engine where it is regulated by the NOS solenoid. The solenoid is an electrically controlled valve which uses a strong electromagnetic field to open a small plunger the blocks the flow of the liquid Nitrous Oxide. A second solenoid is used to supply extra fuel so that the air/fuel mixture remains constant. Both solenoids are controlled by electric switches that activate the electromagnetic field. The NOS system should have at least two switches — a microswitch that is fitted to the accelerator linkage and is only activated at full throttle; and a spring-loaded momentary switch that is activated by the driver. The microswitch on the accelerator linkage ensures that the nitrous system can only be activated at full throttle. Activating the system during part throttle or during a gear change can have very catastrophic consequences. As an added precaution, the oil pressure switch can also be used to ensure that the system can only be activated when the engine is running and there is oil pressure. Starting an engine with NOS in the combustion chamber can also be very catastrophic.

Some more high pressure nylon or Teflon inner-lined braided-steel pipe is used carry the nitrous and fuel (which are still separate at this stage) to the intake manifold where it is released into the engine via two small jets that are located in a special nitrous injector. The jets must be correctly calibrated to release the correct amount of fuel for a given amount of nitrous. In addition, the pressure on the fuel supply side must be adequate and at a constant level to ensure that the air/fuel mixture is correct at all times. This may require the fitting of an electric fuel pump and a fuel regulator.

The quantity of the nitrous flow depends on the size of the jet fitted. A jet is basically a screw with a whole through it. It's used as a restriction tool depending on the size of the link up orifice. Applying a bigger jet is the easiest way to squeeze a bit more power out of your current system. The fuel supply comes from a similar jetting system.

There you have it — the basics behind NOS systems and NOS kits. In our next section we'll look in more detail at NOS installation

Installing a Nitrous Oxide System (NOS)by "Bad Ass" Bre (January 14, 2007)

Installing a NOS kit is a simple process of installing the nitrous tank; a few injectors (which are also called nozzles); and a few solenoids; routing a few meters of tubing (or piping) from the nitrous tank and a fuel line to the solenoids, and the solenoids to the injectors; and then fitting a few switches to arm the electrical circuit that energizes the solenoids. If you are installing a Dry System, you don't need to run a pipe from your fuel line to the fuel solenoid as you don't need to install a fuel solenoid but you will need to modify your EFI system to provide the correct amount of fuel when you engage your NOS system. In my experience, the best way to install the nitrous system is to install the nitrous tank first, followed by the injectors and the solenoids, then connect your feed lines, and connect your solenoids to the battery. This will ensure that each of its elements correctly placed to operate at their full potential. If you are installing a Wet System, you must test the system and ensure that the fuel pressure to your fuel solenoid is constant and adequate. This may require that you install a high pressure fuel pump and/or a fuel regulator.

Begin by installing the NOS tank. The correct installation of the tank is important to getting the most out of your nitrous system. As we've mentioned in our basic nitrous system guide, the NOS tank has a siphon tube that extends from the release valve to the bottom of the tank. The siphon tube reaches the side of the tank on the opposite side of the label. Therefore the tank should be installed at a 15° angle, with the label facing up and the release valve facing the front of the vehicle. This will ensure that more of the liquid N2O is used before the siphon tube begins to pick up gaseous Nitrous Oxide, even under acceleration.

Another consideration is the pressure of the NOS tank. The pressure of the NOS tank will fluctuate as the ambient temperature fluctuates. This can cause problems with the correct calibration of your air/fuel mixture. To overcome this problem, you should ensure that the NOS tank is mounted away from heat sources (such as the exhaust system) and out of direct sunlight. You can also use a NOS blanket to insulate the tank.

You should install the injectors next. The placement of the injectors will depend on whether you're installing a system with a single injector, or a Direct Port System that requires one injector per cylinder. When you need just one injector, you should install the injector as close to the throttle body as possible. If you have a rubber inlet hose connected to your throttle body, you must drill a suitably sized hole to fit the injector, and bolt the injector down with a nut and washer on either side of the hose. If you have a cast aluminum manifold, you must drill a hole and tap a thread into the cast aluminum for the injector to screw into. If you are fitting a Direct Port System, make sure that everything that must be fitted to the intake manifold is in place and find enough space on the manifold to fit the injectors. The injectors must be fitted at the same distance from the cylinder head but try not to fit the injectors too close to the cylinder head. Also, wherever you fit the injectors, apply a little locktight to the thread to ensure that the injector does not work itself loose. If you are installing a Direct Port System, you would need to install a distribution block between the solenoids and the injectors. The purpose of the distribution block is to distribute the fuel and nitrous between the injectors. Although it is not crucial, try to install the distribution block so that the tubes are more or less horizontal. The injectors for a Wet System has two inlets — one for fuel and the other for nitrous. You must connect the right tube to each inlet as indicated on the injector.

The next step is to install the solenoids. These should be installed away from the exhaust manifold but as close to the nitrous injectors as possible. The solenoids must also be installed slightly higher than the injectors to ensure that the nitrous and fuel do not need to flow upward as this will reduce the effectiveness of the system. The solenoids are electrically operated; therefore you'll need to run a few electrical cables to the solenoids.

Once you have your hardware in place, you can install the nitrous and fuel supply lines. It is best to route the tubing that carries the nitrous to the engine bay along the stock fuel line as this would be routed securely, and away from heat sources. The tubing should be secured to the vehicle so that it cannot be damaged by abrasion or by moving suspension and drive train parts. You can use nylon tie-wraps to secure the tubing to the vehicle but ½ inch Tinnerman clamps work much better. The tie-wraps or clamps should be placed no further than 18 inches apart. Whenever you route the tube trough a metal body panel, be user to use suitably sized rubber grommets to prevent the body work from cutting through the tube.

If you are using nylon tubing, you can use a sharp utility knife to cut the tube to the correct length leaving about 2 inches of free play at either end for possible flexing. Never cut the tubing too short and never cut the tube using a scissors or wire snips as this will deform the tube and make fitting the olive and nut quite difficult. Once you have cut the tube to the correct length, slide the nut over the tube with the treaded part facing the end of the tube. Never tighten the nut too much as this will cause the olive to compress the tube and will restrict flow through the tube. Then slide the olive over the tube. Secure the nut to the outlet on the NOS tank while keeping the tube in place and repeat the process at the other end where you must secure the nut to the inlet on the nitrous solenoid. The tube from the solenoid to the injector will require the same treatment. You can install the tube from the fuel solenoid to the injector as well but don't secure the tubing to the fittings on injector just yet — you will need to perform a few tests first. Also beware, the injector for a Wet System has two inlets — one for fuel and the other for nitrous. You must connect the right tube to each inlet as indicated on the injector. Next, tap into your fuel line using a metal T or Y splitter and fit the tubing that will supply fuel to the fuel solenoid and connect it to the inlet on the fuel solenoid.

The final step is to install the electrical circuit that will power the solenoids. The NOS solenoid must lift the plunger against the pressure that can be upwards of 800 psi in the system. A fair amount of current (amps) is required to accomplish this task so make sure that the electrical cables can supply the required amperage to lift the plunger. The electrical circuit should supply both solenoids with power and should incorporate a fuse, a microswitch fitted to the accelerator linkage, an arming switch and a relay. Start by disconnecting the negative terminal from the battery. This will prevent you from causing short circuits while working on the electrical system. Run a live wire from the positive terminal of the battery to the fuse box under the dashboard and on to a relay. Another live wire can then be run from the relay to the relay to the solenoids. This wire must carry sufficient current to activate both solenoids. You can fit the arming switch on the live wire between the relay and the solenoids as this wire will run close to the dashboard area; however it is better to place the switches on the earth wire. The earth wire will run from the solenoids to a suitable metal point on the vehicle's body but it is best to run the earth wire to the negative terminal on the battery. You can fit the microswitch to the earth wire as the solenoids would be placed close to the accelerator linkage.

There you have it, you're done. All that's left now is to test the nitrous system and ensure that the pressure to your fuel solenoid adequate, and then tune the nitrous system for best performance.

Testing and Tuning Nitrous Injection Systemsby "Bad Ass" Bre (February 03, 2007)

TESTING NOS SYSTEMS

Once you have your nitrous system installed, you must test the system to ensure adequate nitrous and fuel flow. This will ensure proper performance and reliability.

Start by ensuring that the fuel line is properly attached to the fuel solenoid and turn the fuel pump on. You can do this by turning the ignition key to the ACC position. Check for fuel leaks where you tapped into the stock fuel line and where the fuel line feeds into the fuel solenoid. Cure any fuel leaks, check again for fuel leaks and then disconnect the fuel line from the nitrous injector. Activate the system and check for fuel flow when the system is activated, and that the fuel stops flowing when you deactivate the system. If you don't get fuel flow, check that the fuel solenoid is operating properly — you should hear an audible click when the solenoid is activated; check that you have fuel flow at the fuel filter; and ensure that fuel line is not kinked, twisted or bent. If you do have fuel flow, turn the vehicle's ignition off and properly secure the fuel line to the nitrous injector.

Now open the release valve on the nitrous tank check for frost along the nitrous feed line. The frost will indicate a nitrous leak. If you find any leaks, close the release valve on the nitrous tank and cure the leaks. Open the release valve again and ensure that you've cured all nitrous leaks. Then disconnect the nitrous line from the nitrous injector. Activate the system and check for liquid nitrous flow when the system is activated, and that the nitrous stops flowing when you deactivate the system. If you don't get nitrous flow, check that the nitrous solenoid is operating properly; and ensure that nitrous line is not kinked, twisted or bent. If you do have nitrous flow, you can properly secure the nitrous line to the nitrous injector.

TUNING NOS SYSTEMS

Nitrous tuning is another simple procedure but you should first tune your engine without nitrous as you will be running without nitrous for most of the time. Tuning the nitrous system is quite straight forward — you start with the jet sizes recommended by the manufacturer of your nitrous system and gradually adjust the jet sizes until the air/fuel mixture added by the nitrous system is perfect.

So install the jet sizes recommended by the manufacturer of your nitrous system. This will be conservative and will err on the rich size (i.e., too much fuel), which is the safe side to err on. Run you engine for a while with the nitrous activated and then check each of your spark plugs to determine how the air/fuel mixture is burning. The correct air/fuel mixture will produce a brownish, grayish-tan color on the spark plugs. If the spark plugs have a sooty, black color, your air/fuel mixture is too rich and you should increase the nitrous jet to the next jet size. If the metal part of the spark plugs displays a bluish or rainbow coloration, go to a smaller nitrous jet size immediately. Repeat this test until your spark plugs display the correct color. Never jump up by more than one jet size on the nitrous side and never try to work your way down from a lean mixture — that's just looking for trouble and major engine damage. You can make more power by increasing the fuel jet size and then adjusting the nitrous jet size up until your spark plugs display the correct color again.

WARNING: Back off as soon as you get detonation and reduce the size of your nitrous jet!

You may also need to adjust your ignition timing as nitrous oxide makes the air/fuel mixture burn much faster than normal. Retard the ignition timing by 2° increments (i.e., less advance before TDC) until you feel a noticeable loss of power. Then advance the ignition timing by 2°.

Now that that's done, your nitrous system is installed, tested and tuned; all that's left is for you to enjoy responsibly — always enjoy power responsibly!

1998 Chevy Cavalier Z24 LD9 2.4L Engine Turbo

1998 Chevy Cavalier Z24 LD9 2.4L Turbo Chargers

1998 Chevy Cavalier Z24 LD9 2.4L Turbo Charging Kits

Turbochargersby "Bad Ass" Bre (December 04, 2006)

The turbocharger, or a just simply the turbo, has been around now for more than a century. It was invented by Swiss engineer named Alfred Buchi in 1905 and was first used on the diesel engines of ships and locomotives from the 1920s. It was used on the engines of production airplanes from the 1930s and on truck engines from the late 1940s. But it only found its way onto the car engine of a production vehicle in 1962 when it was used on the Oldsmobile Cutlass Jetfire.

As a forced induction system, a turbo is nothing more than an air pump that is driven by the exhaust gasses of a car engine. It consists of a compressor-wheel and a turbine-wheel that are connected by a common shaft. The compressor increases the density of the air that enters the intake manifold by forcing more air into the intake manifold than what the car would normally ingest. This higher intake air density contains more air molecules and produces more power when combined with the correct amount of fuel. This is similar to the way NOS allows more fuel to be burned by providing extra Oxygen as explained by Ian. The major difference between NOS and a turbo is that the turbo provides a constant supply of extra Oxygen to the car engine while NOS only provides a limited supply.

You've got three options when it comes to turbocharging a car:

•You can simply buy an OEM turbocharged car such as a Mitsubishi Lancer Evolution, a Nissan GT-R, a Nissan 300ZX, a Nissan Silvia spec-R, a Toyota Supra, etc.

•You can buy an aftermarket turbo kit for your car engine. Here there are many options to choose from. There are Garrett turbo kits, STS turbo kits, Turbonetics turbo kits, and so much more.

•You can also build your own turbo system, which could be the best approach to car engine turbocharging as it gives you the option to build a system that meets your performance requirements and your objectives.

A complete turbo kit consists of the turbocharger as well as the necessary parts required to bolt the turbocharger onto the car engine. This includes an exhaust manifold, intake runners (plumbing to connect the turbo to the intake manifold), and can include an intercooler as well as cooling and lubrication feed lines for the turbo. When building your own turbo system, selecting the perfect turbo for a particular application can be a real challenge as no one turbo is best suited to all applications.

There are a number of things you need to consider when selecting a turbo. These include:

•The capacity of your engine.

•The number of valves.

•At what RPM to you want the turbo to come in.

•The type of fuel you plan on using.

•The turbo boost you plan on running.

•The amount of horsepower you want.

In this custom-car.us turbo guide, we'll thoroughly explain the mechanics of turbochargers and turbo systems and show you how to design and install your own turbo system. As always, the DIY route is not for everyone and if you'd rather install a turbo kit, we cover that too! For now, we'll start with the turbocharger basics ...

Turbo Basicsby "Bad Ass" Bre (December 05, 2006)

Approximately a ⅓ of the energy produced by an internal combustion engine is lost as thermal energy that is fed out the exhaust manifold. It is this energy that is used to drive a turbocharger. When the exhaust gases are forced through the turbine-wheel, the turbine-wheel becomes a reduced-flow area in the exhaust system and causes some back pressure, which causes some loss in engine power. Of course, back pressure increases as the size of the turbo decreases and inversely, back pressure decreases as the size of the turbo increases. So a larger turbo causes a smaller loss in power, but it also requires more air-flow, and hence more RPM, to spin up or spool up and produce boost pressure (i.e. above-atmospheric pressure). This is referred to as turbo lag. So a larger turbo produces less back pressure but has more turbo lag while a smaller turbo produces more back pressure but has less turbo lag. So what is better? The answer to that depends on what you're looking for — low-end torque, top-end power, or a bit of both.

A Garret Turbocharger TURBO LAG

Later on in the series we'll look at turbo sizes, but for now, let's get back to turbo lag. Turbo lag is defined as the time between the point when you hit the accelerator and the point at which the turbo produces enough boost to create boost pressure. This may sound like a bad thing but what would happen if you didn't have a turbo? You'd get no boost! So it's either no turbo lag or no boost. A simple choice, I think, especially when you consider that the loss of power due to back pressure caused by the turbine-wheel is hardly noticeable. Provided you haven't done something silly like lower your compression ratio! In years gone by car manufacturers built production turbo motors with low compression ratios to counter the thermodynamic effect of compressing air. Any time air is compressed, the temperature of the air increases. This affects the internal combustion temperatures in the engine. But when a suitable intercooler is used to cool the intake air, normal compression ratios can be used. With normal compression ratios, you're still getting close to normal aspirated performance until you get boost and then you're flying with an up to 50% increase in bhp, depending on the boost you're running! But let's not get too excited just yet, we'll go back turbo boost first.

BOOST PRESSURE

We've said that turbo lag is the time between the point when you hit the accelerator and the point at which the turbo produces enough boost to create above-atmospheric pressure in the intake manifold. The boost level at which the turbo produces enough boost to create above-atmospheric pressure in the intake manifold is called the boost threshold. This is the point at which the exhaust gas flow over the turbine is high enough to overcome inertia and spin the turbine-wheel fast enough so that the compressor-wheel can begin creating boost pressure. From that point on boost will increase but it is important to remember that the quality of the fuel you run and the temperature of the air pumped into the intake manifold will influence the amount of boost you can run. With normal pump fuel, a stock engine and an intercooler, you can safely run at 7-12 psi boost. A wastegate regulates the boost pressure by allowing exhaust gases to pass around the turbine-wheel so as to limit the exhaust gas flow that drives the turbine-wheel.

But more about wastegates at a later stage; here's something to ponder on for now: A properly installed and tuned turbo operating at 10 psi can reduce the 0-60 mph time by a third, despite turbo lag! Yes, you read right a 10 second car will do 6.66 seconds if the turbo is done right!

Turbo Selectionby "Bad Ass" Bre (December 12, 2006)

There are a number of factors, such as turbo lag, boost threshold, heat, back-pressure, low-end torque, and top-end power, that you must take into account when selecting a turbo. A large turbo will suffer from turbo lag and won't produce much low-end torque but it also won't put too much heat to the intake charge, won't have much back-pressure, and will produce loads of top-end power. A small turbo, on the other hand, won't have much turbo lag and will produce loads of low-end torque but will also have lots of back-pressure and will add lots of heat to the intake charge. You can't have the best of both worlds but you can select the best turbo to suit your needs.

Deciding which turbocharger best suits your needs in a bit complicated. You need to know what your objectives are — street car, a purpose built ¼ miler, a race car, or a rally sprint car. Once you know what you want, you should have a better idea of at what rev range you want your power band to be. Once you know that, then it becomes easier as you can select a compressor-wheel to match your rev range.

SELECTING THE COMPRESSOR WHEEL

The compressor-wheel is most efficient at a particular boost pressure or pressure ratio (PR) and air flow (cfm). At this point the turbo will put the least amount of heat into the intake charge; anywhere else, including at lower boost pressures or revs, it will put more heat into the intake charge. The idea id that the point of efficiency should coincide with your most useful rev range. So it's a matter of determining the bore diameter of the compressor wheel that is most efficient at your most useful rev range; and by most efficient, I mean at least 60% efficient. Each compressor-wheel has a compressor map that maps efficiency at various pressure ratios and air flow rates but you need to calculate the air flow rate for your engine. You can use the following formula to calculate the air flow rate:

PR × CC × ½RPM × VE

In this formula, PR is the Pressure Ratio. This is the absolute pressure produced by the turbo divided by atmospheric pressure. Atmospheric pressure is 14.7 psi at sea level. If you're running 7 psi of boost, your absolute boost pressure is 21,7 psi (7 psi + atmospheric pressure). This will give you a PR of 1,47 (21,7 ÷ 14,7), which means that approximately 47% more air/fuel mixture is being forced into each cylinder.

We halve the RPM because a four stroke internal combustion engine requires two revolutions to complete one power cycle

CC is engine capacity but in cubic feet and not in cubic inches. Why cubic feet? Because cfm is cubic feet per minute. You can convert engine capacity to cubic feet by dividing cubic inches by 1728.

VE is volumetric efficiency. This is the total amount of air/fuel mixture that each cylinder ingests during the intake stroke and is expressed as a percentage of the actual volume of the cylinder. You can calculate the VE as follows:

2 × mass airflow rate

air density × swept volume × RPM

Yes, I know, it's getting a bit complicated! Fortunately we can use a rule of thumb that states that modern engines have a VE of 80-90% while older engines like the Datsun L-series engine have a VE of 60-70%!

SELECTING THE TURBINE WHEEL

The turbine-wheel uses exhaust gas energy to spin the compressor-wheel fast enough to produce the required air flow rates at the desired boost pressure. A larger turbine-wheel will produce more power to spin the compressor-wheel at the required air flow rates, although s smaller turbine-wheel will spin faster. A smaller turbine-wheel will also offer greater restriction to the exhaust gas flow, causing back pressure between the turbine-wheel and the combustion chamber. So the basic size of the turbine wheel will be determined by the air flow required from the compressor-wheel. The important element here is the extruder bore size, i.e., the inner diameter of the turbine outlet. An extruder bore with a 2 inch diameter will be sufficient for a compressor-wheel air flow of 250 cfm to 400 cfm; an extruder bore with a 2½ inch diameter will be sufficient for a compressor-wheel air flow of 400 cfm to 500 cfm; an extruder bore with a 2¾ inch diameter will be sufficient for a compressor-wheel air flow of 500 cfm to 600 cfm; an extruder bore with a 2⅞ inch diameter will be sufficient for a compressor-wheel air flow of 600 cfm to 800 cfm; and an extruder bore with a 3 inch diameter will be sufficient for a compressor-wheel air flow of over 700 cfm.

CONSIDERING THE A/R RATIO

The A/R ratio is another important consideration in choosing the turbine-wheel. The A/R ratio is the ratio between the cross-sectional area (A) of the turbine scroll at any one point and the distance or radius (R) from that point to the center of the turbine-wheel. This ratio is always constant so each point along the turbine scroll will have the same A/R ratio. A turbo with a smaller A/R ratio will tend to create more torque while a turbo with a larger A/R ratio will provide more power because more exhaust gas energy will be acting on the turbine-wheel. Generally, an A/R ratio of 0.7 will provide better low-end response, while an A/R ratio of 1.4 will provide more top-end power.

OTHER CONSIDERATIONS

Other important factors that you should take into account when selecting the turbo include cooling and the location of the wastegate. As I've mentioned in our turbo lubrication section, a turbo with a water cooled bearing section will have a longer lifespan and will be more reliable because it solves a few major lubrication issues. We discuss wastegates in our turbo boost control section but the short of it all is that a turbo with a remote wastegate produces more power, but a turbo with an integrated wastegate is much cheaper.

Turbo Bearings and Lubricationby "Bad Ass" Bre (December 10, 2006)

Lubricating the shaft inside the turbo is not too difficult and most turbo manufactures provide adequate oil feeds to the shaft's bearing housing. However, the extremely high temperatures that the turbine creates will cause the oil in the bearing housing to disintegrate and loose its viscosity and lubricating qualities and will cause coking in the turbo bearing housing. Coking will impede the flow of oil to the bearing and will exacerbate the problem. Four things contribute to coking:

•High temperatures in the turbo's bearing housing

•Using engine oil that is not capable of operating in high temperatures

•Using engine oil that has a wide multi-viscosity range — the additives used to achieve multi-viscosity are the material that causes coking

•Not changing the engine oil frequently enough

There are two simple solutions to this problem:

•Change the engine oil more frequently

•Get a turbo with a water jacket around the bearing housing. It might be a good idea to look out for a turbo with a water jacket around the bearing housing when selecting a turbo

The best engine oil you can use in your turbo engine is a synthetic, straight viscosity oil that is suitable for the temperature range of both the climate in the area that you live, and the engine.

The important thing is to change the engine oil and oil filter regularly. Even if the turbo has a water jacket around the bearing housing, you should still change the engine oil more frequently than on naturally aspirated engines, and you need to do this diligently! Changing the engine oil every 2,000 miles should do the trick.

You also need to ensure that the oil pressure to the turbo does not exceed 70 psi or else that oil will push past the oil seals in the turbo and cause frequent, if not continuous, smoking. If your oil pump produces more oil pressure than the turbo’s seals can handle, you should install a restrictor in the oil feed line, or a bypass system to reduce the oil pressure to the turbo. A bypass system is more reliable but in both cases you must ensure that the oil pressure to the turbo is adequate at idle and at full operation.

The oil seals in the turbo do not operate properly if they are bathed in oil, therefore, you should ensure that the oil return line to your oil sump is big enough to allow for proper drainage. The oil return line should have an inner diameter of at least a ½ inch. The oil drain hole in the turbo should also be aligned as near vertically downward as possible.

Best practice to ensure that your turbo lasts is to cruise at low RPM where no boost pressure is created for the last 15 minutes of your journey to let the turbo cool down properly. Some people suggest that you let the engine idle for 30 seconds before turning off the engine, or install a turbo timer to automate the task, but the oil pressure at idle speeds is too low to provide sufficient lubrication. You need at least 1,500 RPM for enough oil pressure to ensure that the bearings and shaft receives sufficient lubrication while the turbo cools down. It is for this reason that we do not recommend installing a turbo timer. You should also change the engine oil every 2,000 miles, and use a high-quality, synthetic, straight viscosity oil. These three simple things will ensure that you prolong the life of your turbo and that you never need worry about coked up turbo bearing failure again.

Turbochargers and Intercoolersby "Bad Ass" Bre (December 20, 2006)

Intercoolers reduce intake heat Although it is not a performance part per se, an intercooler is nevertheless a fundamental part of a turbocharger system. While there are two types of intercoolers on the market — air-to-air and air-to-water intercoolers, only air-to-air intercoolers are practical on street and endurance type racing cars. Air-to-water intercoolers work wonders on extremely short runs and are ideal for drag cars. You can think of an as a radiator that cools the compressed air that compressor-wheel pumps into the intake manifold. This compressed air is referred to as the intake charge.

Heat is a byproduct of the compression of air and whenever air is compressed, such as when turbochargers and other forced induction systems are used, the air (intake charge) is heated. This is called the thermodynamic effect of compressing air. On an internal combustion, air temperature is important because it affects air density and because too much heat will result in pre-ignition, knocking and detonation. The role of the intercooler is to reduce the temperature of the intake charge. Cooling the intake charge provides two major benefits: it makes the intake charge denser — denser air produces more power; and it inhibits detonation. However, the intercooler has one major disadvantage: it causes a drop in boost pressure! This is inescapable; the best you can do is to minimize the pressure loss caused by the intercooler.

There are a number of things you can do when designing your intercooling system to keep pressure loss at a minimum. You can incorporate a plate-and-shell core rather than an extruder core as the plate-and-shell core produces less flow resistance. The internal flow area of the core also affects pressure loss. Selecting an intercooler with the correct internal flow area is important to keep pressure loss at a minimum. Here I have found that a turbo system that produces a flow rate of 400 cfm requires an internal flow area of approximately 20 sq in. You can use the following graph to estimate the required internal flow area based on your turbo's flow rate.

Once you've estimated an idea of what internal flow area you require, you can determine the actual core size that you require. This is a bit tricky. Typically, only about 45% of the intake charge will come into contact with the heat exchange elements of the intercooler core. So we must first divide the required internal flow area by 45% then divide the result by the core thickness. This gives us the following formula:

internal flow area ÷ 0.45

core thickness

While we're talking about core thickness, remember that the intake charge flows through the length of the core and the cooling, ambient air flows through the thickness of the core but that every subsequent inch of core thickness is 40% less effective as the air flowing through it heats up. Thus, a thinner core intercooler with a larger fontal area is more efficient than a thicker intercooler with a smaller frontal area.

You can also improve the efficiency of your intercooler by fitting a duct to it. Without a duct, approximately 25% of the air molecules will pass through the core; the rest will follow the path of least resistance around the core. Any improvement here will greatly increase the efficiency of your intercooler.

If you're running high boost pressures on 91-93 octane gas and a fairly high compression ratio, you may also want to supplement your intercooler with a water injection system.

Water Injectionby "Bad Ass" Bre (March 15, 2008)

On turbocharged cars water injection can also be used to cool the intake charge and reduce the possibility of detonation, though some engine tuners to frown upon it. Nonetheless, water has a very high specific heat capacity, which means it can absorb a lot of heat energy without a significant increase in temperature. As a result, water injection systems have been around in one form or the other since 1936 and were used on a variety of aircraft engines during World War II. However, water injection is only required if you're running high boost of more than 12 psi, and should be used in conjunction with a good intercooler.

The water injection system basically consists of a storage tank, a water injector, which is similar to a fuel injector, a high pressure pump, a pressure sensor connected to the intake manifold, and an intake air temperature sensor. Calling it water injection is possibly inaccurate as it can wither be pure water, preferably distilled water, or a mixture of water and methanol. Either way, atomized liquid is usually injected into the intake system when the intake air temperature is exceeding a certain value and the engine is on boost and is usually injected downstream of the intercooler.

HOW WATER INJECTION WORKS

Atomized water rather, that vaporized water is injected into the air intake system as water only boils at 212° F at sea level while temperature of the intake charge would be much lower, having already passed through the intercooler. When water is injected into the air intake system it absorbs quite a bit a heat from the intake charge. When the atomized water, together with the intake charge, enters the combustion chamber, the high temperature of the combustion chamber causes the atomized water droplets to vaporize. During the process of vaporization a large amount of heat energy is absorbed, resulting in anther drop in intake charge temperature! Unfortunately, vaporized water also displaces a large volume that would have been filled with air molecules, but the lowered temperature in the combustion chamber more than makes up for this loss in volume. Indeed, the lowered temperature in the combustion chamber allows us to run higher boost pressures and, consequently, allows us to make more power!

WATER AND METHANOL

Some engine tuners prefer to inject a mixture of water and methanol into the intake system. Usually 50% methanol by weight is used. This provides the desired detonation suppression while also providing maximum horsepower. Methanol is both hygroscopic, which means it absorbs water, and miscible, which means it mixes well with water. It is also much more volatile than water, which means it vaporizes much quicker. This vaporization further reduces the temperature of the intake charge, but it occurs before the combustion chamber is reached. Once the combustion chamber is reached, the atomized water droplets vaporize so temperatures are still reduced in the combustion chamber. But methanol is also a fuel and thus provides extra horsepower as well.

DISADVANTAGES OF WATER INJECTION

There are some disadvantages to using a water injection system, some of which can be catastrophic! Firstly, a failure in your water injection system would mean a complete lack of detonation suppression, which could quickly lead to engine failure! To prevent such a scenario, you need a failsafe system that will cut engine power when the intake charge temperature downstream from the water injector reaches a certain threshold. Secondly, the minerals in tap water will quickly clog up the water injector and will result in a failure to deliver the correct amount of water. For this reason you should use distilled water in your water injection system. As with any other system, you need to ensure that only quality hoses and clamps are used in order to ensure the reliability of you water injection system.

Finally, determining the correct amount of water that needs to be injected can be pretty tricky as you do not want high boost pressure with too little detonation suppression! The safest way of reaching the correct amount of water injection for a particular application is to start with a lower boost pressure and slowly increase boost pressure. If detonation occurs, back off immediately and increase the water injection if a greater boost pressure is required

Boost Controlby "Bad Ass" Bre (December 21, 2006)

A turbocharger increases its airflow rate much faster than an internal combustion engine can adapt to the increase in airflow. If left unchecked, the turbo will almost instantaneously produce extremely high boost pressures with catastrophic results on the engine. To prevent this catastrophe, we need to regulate the boost pressure that the turbo can produce so as to prevent overboosting. This is where the wastegate comes in.

A wastegate is a mechanical device that controls boost pressure by regulating the exhaust gas energy that flows around the turbine-wheel by bleeding off excess exhaust gas energy. In so doing the wastegate controls the speed at which the turbine-wheel can spins. The turbine-wheel drives the compressor-wheel, which in turn produces boost pressure. The wastegate is held shut by a spring. As boost builds, the wastegate actuator diaphragm pushes the wastegate open against the spring. The size of the diaphragm and strength of the spring determine how much boost is required to open the wastegate.

There are two types of wastegates on the market: integral wastegates that are built into the turbo; and remote wastegates that are integrated into the exhaust system ahead of the turbo. The remote wastegate allows for a bigger valve and a smoother flow path which provides better boost control and produces better performance. A remote wastegate can also be controlled by a manual boost controller or by an electronic boost controller. The manual boost controller begins opening gradually as the boost pressure builds up. This affects the efficiency of the turbo system and increases turbo lag. An electronic boost controller, on the other hand, can be programmed to open at a preset boost pressure and can even be programmed for increased boost under certain circumstances. Needless to say, the electronic boost controller is the way to go!

The exhaust feed for the remote wastegate should be integrated into the exhaust header so that it is exposed to as much of the pressure in the exhaust system as possible. This means that the pipe for the wastegate should be connected at or after the collector where all the primary exhaust pipes join together, or after the last exhaust port on a log-type header. Also, the wastegate should be located at an angle that does not restrict exhaust gas flow to the wastegate. The exhaust gas must be able to flow to the wastegate so that the wastegate can detect the correct exhaust pressure in the system. A Y-pipe that provides symmetry and easy flow paths would be ideal.

The exhaust gas flow from the wastegate into the tailpipe should also not interfere with the gas flow from the turbine. Any interference will increase back pressure! For best performance, the pipe that feeds exhaust gas from the wastegate to the tailpipe should be at least 18 inches long. A completely separate tailpipe for the wastegate exhaust gas would be even better as this provides the best wastegate response and the lowest back pressure. When going this route remember to allow for tailpipe expansion as the tailpipe from the wastegate will experience fluctuations in temperature. However, in most road cars legislation requires that your wastegate feed back into the main exhaust system ahead of the catalytic converter.

Whether you use a electronic boost controller or not, you should have an emergency boost control device in case the wastegate fails. This device can be a simple vent valve or a boost-sensitive electronic switch that cuts the fuel supply. A boost-sensitive electronic switch that cuts the fuel supply can be set to 1 or 2 psi above the wastegate setting. Should the wastegate fail, the cut-out switch will stop the fuel supply, which will cause the boost pressure to drop.

1998 Chevy Cavalier Z24 LD9 2.4L Super Charging

1998 Chevy Cavalier Z24 LD9 2.4L Super Chargers



1998 Chevy Cavalier Z24 LD9 2.4L Super Charging Kits



Superchargers and Blowersby "Bad Ass" Bre (January 06, 2007)

The centrifugal type supercharger In general terms, a supercharger, which is also commonly known as a blower, is nothing more than a large air pump that is driven by a belt that runs off the crankshaft of an engine. Superchargers have been used on car engines for more than a century already, with the German car manufacturer, Gottlieb Daimler, being credited as the first person to patent a supercharger system for an internal combustion engine. His design was based on the twin-rotor air pump designed by the Americans, Philander and Francis Roots in 1859 and patented in 1860. The first production vehicles to use superchargers were built by Mercedes and Bentley in the 1920's.

Superchargers have become quite common in the car performance industry in recent years, and are even installed as original equipment on some new high performance cars. They have become popular because of their cost efficiency and reliability, but mainly because of their performance. Indeed, supercharging a car engine results in huge power increases between 50% and 100%, making them great for racing and car customizing. In fact, back in the 1980's, there was probably nothing that shouted 'hot rod' louder than a Chevy V8 with a large Roots supercharger sticking out through the hood. But supercharging has come a long way since the 1980's when superchargers were rather inefficient and struggled to make 3 pounds of boost. Today you can walk into any performance parts shop and order any number of efficient Roots supercharger and centrifugal supercharger kits designed specifically for your engine. And with supercharging technology being so advanced, those superchargers could easily double the horsepower of a stock car engine! That's more horsepower than you would ever need!

When people start thinking about fitting a supercharger there are usually two things that they are concerned about. First, they think that the added boost will put strain on the engine parts and will lead to engine damage; but this is not necessarily true. Engine damage is usually caused by excessive RPM but a supercharged engine will make the same amount of horsepower substantially lower RPMs than a stock engine, making high RPMs less of a necessity. The second concern is that some people think that by increasing the engine's compression, a supercharger will cause detonation in the combustion chamber. However, unlike turbochargers, most superchargers do not cause 'overboost' conditions. Superchargers are also designed to operate a boost pressures will not cause detonation, while most superchargers kits also include an intercooler to further detonation while other supercharger kits include a boost timing retard chip that retards the engine's ignition timing under high boost conditions.

A more pertinent consideration should be what supercharger to use, especially with all the different types of superchargers available these days. Choosing the best supercharger for your particular engine can be a bit of a challenge as no single supercharger can be described as "the best". All superchargers work well, and they all have their strengths and weaknesses. What you need is an idea of what you want from the supercharger and an idea of what to expect from each type of supercharger. Especially as different vehicles and different engines may benefit from one type or another; so it's important that you know what you're looking for.

There are two types of superchargers that are commonly used on an internal combustion car engine:

•Centrifugal superchargers, which are very similar to turbochargers; and

•Positive-displacement superchargers, such as the Roots supercharger and the twin-screw supercharger.

Furthermore, there are two different types of positive-displacement superchargers: the twin-screw supercharger and the Roots supercharger, but both are based on the same design principles but they use different types of lobes. Then there is also the sliding vane supercharger, which is not widely used on car engines and won't be discussed here. Of the three superchargers, the centrifugal supercharger is becoming more popular because of its compactness.

In this section we'll discuss the different types of superchargers, and what to expect from each one of them, as well as intercoolers. But we'll start as always with supercharger basics where we'll discuss how the different types of superchargers work

The Basics Of Super Chargers And Blowers

Supercharger Basicsby "Bad Ass" Bre (April 12, 2007)

A supercharger is simply a mechanical device that forces more air and fuel into an internal combustion engine. The more air and fuel that can be forced into an engine, the more power it can produce. It sounds a lot like a turbocharger and it is very similar to the turbocharger, except that a supercharger is driven off the engine rather than the engine's exhaust system. This can rob the engine of as much as 20% of engine power. But this is more than compensated for by the increase in power that the supercharger produces. Despite this difference, a centrifugal supercharger can be described as a belt driven turbocharger. A positive-displacement supercharger is somewhat different in design, but we'll get to that in a little while.

Increasing pressure with a supercharger, as with a turbocharger, will result in increased intake air (or intake charge) temperatures. The increase in air temperature is a result of the thermodynamic effect of compressing air. A term called adiabatic efficiency is a measure of how much more the supercharger heats the air than the thermodynamic effect. Thus a more efficient supercharger will result in a cooler intake charge. The cooler the intake charge, denser it is; and denser air makes more power. A cooler intake charge is also less prone to detonation. Like a turbocharger, a supercharger will benefit from the fitting of an intercooler.

Obviously, the higher the pressure, the higher the temperature and the lower the density. This means that at some point, increased boost will result in a temperature rise that offsets the pressure increase. At that point, the additional horsepower created by the supercharger is offset by the power required to spin the supercharger.

POSITIVE-DISPLACEMENT SUPERCHARGERS

There are two basic types of superchargers: positive-displacement superchargers and centrifugal superchargers.

The superchargers fitted to classic hot rods are positive-displacement superchargers of which the Roots supercharger is an example. These superchargers consist of two lobe rotors or two screws that spin inside an aluminum housing. The Roots supercharger uses two lobe rotors. They are also widely used and usually the most cost efficient supercharger.

However, the required internal clearance between the lobes and the housing means that the positive-displacement supercharger is usually considered to be the least efficient supercharger. However, recent engineering developments have resulted in a more efficient Roots supercharger with an adiabatic efficiency of 50-60%.

The screw-type supercharger does not suffer from the same internal leakage and has an adiabatic efficiency in the region of 70%.

Positive displacement superchargers work by pumping air into the intake manifold at a faster rate that the engine would normally ingest. These superchargers are referred to as 'positive-displacement' superchargers because they pump air at a fixed rate in relation to engine speed and supercharger size. Therefore, there is not threat of over boost. Positive displacement superchargers are also more effective at producing compression at low engine speeds than centrifugal superchargers as they do not need to spool up.

The major disadvantage of positive-displacement superchargers is their size. To create more boost you need a bigger supercharger. This usually means that there is no place for the supercharger inside the engine bay. They also generate lots of heat but this can be tempered by using an intercooler.

CENTRIFUGAL SUPERCHARGERS

The centrifugal supercharger has become quite popular in recent times, mainly because it is much smaller than a positive-displacement supercharger. The centrifugal supercharger is a completely different design to the positive-displacement superchargers and has more in common with a turbocharger. Indeed, the centrifugal supercharger housing is similar to that of a turbocharger and it uses an impeller wheel rather than lobes or screws to move air. The centrifugal supercharger uses step-up gears to spin the impeller wheel much faster than the rotors or screws in positive-displacement superchargers. But this means that the supercharger must 'spool' up before it creates boost.

These superchargers are also true compressors rather than air pumps. The air is drawn in by centrifugal force created by the impeller wheel and passes through a vaneless diffuser. The air is then sent into a scroll where it is compressed. Obviously, the size of the impeller wheel and the step-up gear ratio will determine the boost pressure produced by the centrifugal supercharger.

Because the centrifugal supercharger uses step-up gearing, its displacement is not proportional to its size and a smaller supercharger can be used to create greater boost. Because they are much smaller, centrifugal superchargers can be mounted at the front of the engine rather than on top of it.

Despite being described as a supercharger, the centrifugal supercharger could fall into the turbocharger category in the great supercharger vs turbocharger debate.

The Roots Superchargerby "Bad Ass" Bre (May 22, 2007)

The Roots supercharger, or the Eaton supercharger as its also called, is the oldest type of supercharger around, having been designed by the Roots brothers in 1859 as an air pump for use in the mining industry. The Roots or Eaton supercharger is a positive-displacement supercharger that consists of at least two lobed rotors housed in an aluminum casing. The rotors are meshed together and geared to rotate in the opposite directions. As the lobes turn, air trapped in the space around the lobes and is forced along the inside of the casing until it is discharged into the intake manifold. Being a positive-displacement supercharger, it moves air at a fixed rate in relation to engine RPM; hence a larger capacity Roots supercharger is required if you want to achieve higher boost levels.

Since the 1950's, engineers at the Eaton Corporation have been redeveloping the Roots-type supercharger. In the mid 1970's they made significant breakthroughs when they developed the twisted rotor for the Roots supercharger to improve its thermal efficiency to 50-60% and reconfigured the Roots supercharger's outlet port to reduce noise levels. The Eaton Corporation has also improved the fuel efficiency of the Roots-type supercharger. This resulted in the Roots supercharger also being referred to as the Eaton supercharger and it made the Roots supercharger an attractive option for both car manufacturers and hot rodders. They are also popular with muscle cars and hot rods as the Roots-type supercharger is usually installed on top of the engine and sticks out of the hood of the car.

However, the Eaton supercharger and the Roots supercharger does not compress air but simply moves air at a fixed rate in relation to engine RPM. In this sense it is nothing more than an air blower with air compression taking place externally. In other words, the Roots supercharger produces boost pressure by stacking more and more air into the intake runners and into the intake manifold. Thus, with the Roots and Eaton supercharger, boost pressure is the result of more air being forced in to the intake runners and into the intake manifold and boost pressure only increases after the air is discharged from the supercharger. Hence the Roots supercharger is also called an external compression supercharger. This external compression is also a major contributor to the relatively poor thermal efficiency of the Roots supercharger.

THE PROS & CONS OF ROOTS-TYPE SUPERCHARGERS

If you're looking for a cost effective, low boost supercharger with excellent boost at low RPM then the Roots-type supercharger may just be your best option. However, these types of superchargers do suffer from internal leakage, which reduces it efficiency at low RPM. Furthermore, the Roots supercharger draws the most engine power of all types of superchargers and also has the least thermal efficiency of all superchargers. However, its simple construction with few moving parts makes the Roots supercharger one of the most reliable types of superchargers you can find. The Roots supercharger also doesn't suffer from surge as it is a positive displacement supercharger, which means that it moves air at a fixed rate in relation to engine RPM. This also means that a large capacity Roots supercharger is required if you want to achieve higher boost pressures. However, if you're looking for boost pressure of over 12 psi, you'd have to look elsewhere as the poor thermal efficiency of the Roots supercharger becomes a major problem at higher boost pressures. Although, they work wonders on exotic fuel dragsters that are used for short bursts of around 15 to 20 seconds at a time and were boost from low RPM is more important than thermal efficiency, they are not ideal for constant high boost applications.

THROTTLE PLACEMENT

When implementing a Roots supercharger, you must install a bypass valve and relocate the throttle body ahead of the supercharger's inlet port. If you don't move the throttle body, the supercharger will build up pressure between the supercharger and the throttle whenever your foot is off the accelerator, such as when you're idling, decelerating, or changing gears. When the pressure between the supercharger and the closed throttle exceeds the boost pressure being supplied by the supercharger, the air will be forced back through the supercharger. However, air can only move in one direction through a Roots-type supercharger. If the air tries to flow back through the supercharger, the supercharger will cease and will destroy the drive belt. This can also cause the throttle plate to buckle and get jammed in the throttle bore as the pressure will not be released. Of course, moving the throttle body further away from the intake valves will make the engine less responsive to throttle input, but that's just the cost of running a positive-displacement supercharger.

The Lysholm or Twin-Screw Superchargerby "Bad Ass" Bre (May 23, 2007)

A twin-screw or Lysholm supercharger for a Nissan 350Z

The twin-screw supercharger is quite similar to the Roots-type supercharger but has a few significant differences. The twin-screw supercharger was first patented by Heinrich Krigar in Germany in 1878 when it was developed as an air pumping compressor for industrial use. However, lack of precision engineering prevented the further development of the supercharger. With improvements in engineering precision, a Swedish engineer named Alf Lysholm was able to further developed the twin-screw supercharger in the 1930's for gas and steam turbine use. Lysholm developed the profile of the rotor lobes and testing various rotor lobe combinations and is credited with developing the modern twin-crew supercharger to the extent that the twin-screw supercharger is also referred to as the Lysholm supercharger.

Like the Roots-type supercharger, the twin-screw supercharger falls in the category of positive-displacement superchargers. It consists of counter-rotating rotor lobes housed in an aluminum casing, but the twin-screw supercharger differs in that it is not just an air blower but an air compressor that builds boost pressure internally. This internal compression is brought about by the profile and shape of the counter-rotating lobes. The two lobes do not overlap completely, leaving a small air pocket between them, which become gradually smaller as the air pocket moves through the supercharger and increases the air pressure. The lobes in twin-screw superchargers must thus be manufactured with high precision to ensure that internal leakage does not occur as internal compression increases.

THE PROS & CONS OF THE TWIN-SCREW SUPERCHARGER

As it is based on the same principles as the Roots-type supercharger, and because it is a positive-displacement supercharger, the twin-screw or Lysholm supercharger has many of the benefits of Roots-type superchargers but few of its disadvantages. As a positive-displacement supercharger it has excellent boost at low RPM but it is more efficient than Roots-type superchargers as its rotor lobes are manufactured to greater precision that does not allow for internal leakage. However, this and the complexity of its rotor design make the twin-screw supercharger much more expensive to produce.

Also, because the twin-screw supercharger develops compression internally, it has a much better thermal efficiency of 70-80% compared to the 50-60% of the Roots supercharger. The improved thermal efficiency makes the twin-screw supercharger ideal for applications that require medium to high boost with good boost starting from low engine RPMs. However, the stronger construction is required to withstand internal compression, increasing the cost of manufacture.

Furthermore, because the twin-screw supercharger is a positive-displacement supercharger with internal compression, it produces more noise than the Roots supercharger that has external compression. Due to the internal compression, the air surges out as it leaves the supercharger, which causes an increase in noise levels. This, however, has not stopped car manufacturers from implementing twin-screw superchargers on high performance cars, such as the Mercedes-Benz SLR McLaren and the Koenigsegg CC8S.

THROTTLE PLACEMENT

As with the Roots-type supercharger, you must install a bypass valve and relocate the throttle body ahead of the supercharger's inlet port when implementing a twin-screw supercharger. If you don't move the throttle body, the pressure between the supercharger and the throttle plate will build up on idle, or when decelerating or changing gear. When the pressure between the supercharger and the closed throttle exceeds the boost pressure produced by the supercharger, the air will be forced back through the supercharger. This will cause the supercharger to cease as air can only move in one direction through a positive-displacement supercharger. As a result, the drive belt could be destroyed and the throttle plate could buckle and get jammed in the throttle bore as the pressure will not be released. However, relocating the throttle body will result in poor throttle response but this is unavoidable.

The Centrifugal Superchargerby "Bad Ass" Bre (May 24, 2007)

A centrifugal supercharger from Vortex The centrifugal supercharger gets its name from the way it pumps air into the intake system. This type of supercharger has a belt driven impeller or compressor wheel that draws into the center of the supercharger and uses centrifugal force to force the air out radially and into a circular scroll that increases in diameter as it moves further away from the center of the supercharger. This slows the flow of the air while increasing the pressure of the moving air. This is quite similar to the way a turbocharger works, which means that this type of supercharger has more in common with the turbocharger than with positive-displacement superchargers. In fact the centrifugal supercharger's compressor wheel is quite similar to that of a turbocharger and some centrifugal supercharger manufacturers have even implemented compressor wheel technology that has been developed for the turbocharger! The circular scroll is also similar to that of the turbocharger.

A major difference between the centrifugal supercharger and the turbocharger is that the compressor wheel of the centrifugal supercharger is usually driven by a belt and step-up gears rather than by the exhaust gasses. The use of a step-up gear means that the centrifugal supercharger is not a positive-displacement supercharger. Instead its air-flow rate increase at the square of its shaft RPM, which is significant as the compressor wheel must spin at very high RPMs in order to produce significant amounts of boost. It also means that the boost pressure increases with RPM. Thus, the centrifugal supercharger will make high amounts of boost pressure in the upper RPM range.

THE PROS & CONS OF CENTRIFUGAL SUPERCHARGERS

Unlike a positive-displacement supercharger, the centrifugal supercharger produces low boost pressures at low RPM by design. This is because high boost pressures at low RPM will result in excessively high boost pressures at high RPM because the air-flow rate from the centrifugal supercharger increases at the square of its shaft RPM! However, because it produces internal compression, the centrifugal supercharger has excellent thermal efficiency of 70-85%, making it the most thermally efficient type of supercharger. This improved thermal efficiency makes the centrifugal supercharger ideal for high boost applications. The other major advantages that the centrifugal supercharger has over the other types of superchargers are its compact size and its ability to free-wheel when boost pressure isn't required.

The compact size of the centrifugal supercharger makes it easier to install the supercharger in the engine bay. The centrifugal supercharger can also be mounted far away from the air intake, making it possible to incorporate an intercooler, and making it even more adaptable and easier to install. Its compact size also means that the centrifugal supercharger consumes less engine power, and because it requires less engine power, the centrifugal supercharger can use a relatively thin drive belt when compared with those of the positive-displacement superchargers.

In addition, the centrifugal supercharger is able to "free wheel", which means that it is not adversely affected when air flows backward through the supercharger, as may occur under quick deceleration or while changing gears. This means that the throttle body does not need to be moved or relocated to the front of the supercharger as is the case with positive-displacement superchargers. This means that stock throttle response will not be compromised. What happens when the throttle is closed at high RPM, such as when you change gears, is that the pressure between the supercharger and the closed throttle will build up until it exceeds the boost pressure being supplied by the supercharger. The air between the supercharger and the closed throttle will then flow back through the supercharger relieving the pressure. The reverse air flow back through the supercharger is called surge and doesn't cause any harm. However, it does contribute to the noise produced by the centrifugal supercharger. Though this noise caused by surging can be mitigated by installing a blowoff valve either at the supercharger outlet port or near the throttle plate. However, the main source of noise caused by a centrifugal supercharger is the result of the step-up gears that allow the compressor wheel to spin at speeds in excess of 40,000 RPM. Powerdyne counteracts this noise in their Silent-Drive centrifugal superchargers by using an internal belt to drive the compressor wheel rather than step-up gears.

But the biggest disadvantage of the centrifugal supercharger over its positive-displacement counterparts is the low boost pressures produced at low engine RPMs. As we mentioned earlier, this is because the centrifugal supercharger's air-flow rate increases at the square of its shaft RPM. The result is that a centrifugal supercharger will typically produce maximum boost at the engine's redline with hardly any boost pressure below 2,000 engine RPM. However, boost pressure does build quite quickly in the upper half of the engine's powerband.

CONCLUSION

The lack of low boost at low engine RPM means that the centrifugal supercharger would be suitable for quick reving, light cars with manual transmissions rather than heavier vehicles or vehicles with automatic transmissions. Thus, if you have a truck or a car with an automatic transmission, a positive-displacement supercharger, which makes full boost as low as 1,500 engine RPM, would be a better option.

Superchargers and Intercoolersby "Bad Ass" Bre (December 20, 2006)

You can think of an intercooler as a radiator that cools the compressed air (intake charge) that the supercharger pumps into the intake manifold. There may be two types of intercoolers on the market — air-to-air and air-to-water intercoolers but, although air-to-water intercoolers work wonders on extremely short runs and are ideal for drag cars, they are not practical street- and endurance type racing cars. For street- and endurance type racing cars you would need to use an air-to-air intercooler.

As with turbocharged cars, an intercooler is not a performance part per se, but it performs a fundamental and important role in a supercharged engine to maintain engine reliability. Its main purpose is to cool the intake charge. Reducing the temperature of the intake charge has two benefits: it makes the intake charge denser and denser air produces more power as it has more air molecules per cubic inch; and it reduces the possibility of detonation. Unfortunately, the intercooler has a major disadvantage: it is an obstacle in the intake charge path and causes a drop in boost pressure! Unfortunately there is no way of getting around this problem and the benefits of having an intercooler far outweighs this disadvantage. The best you can do is to maximize the efficiency of the intercooler and minimize the pressure loss caused by it.

You can minimize the pressure loss caused by the intercooler by designing efficient intercooling systems that to keep pressure loss at a minimum. Firstly, you should use a plate-and-shell core rather than an extruder core as the plate-and-shell core offers less resistance to air flow. Secondly, the internal flow area of the core has a major affect pressure loss. Therefore you should select an intercooler with the correct internal flow area in order to keep pressure loss at a minimum. The following graph is a good tool to estimate the required internal flow area based on your supercharger's flow rate.

As you can see on the graph, a supercharger that produces a flow rate of 300 cfm requires an internal flow area of approximately 15 sq in. Once you have estimated the internal flow area your supercharger requires, you can determine the actual core size that you need. This can be a bit tricky as only about 45% of the intake charge will come into contact with the heat exchange elements of the intercooler core. Therefore you must first divide the required internal flow area by 45% then divide the result by the core thickness. This gives us the following formula:

internal flow area ÷ 0.45

core thickness

Thirdly, you need to remember that every subsequent inch of core thickness is 40% less effective than the previous inch as the temperature of the ambient air flowing through it increases as it takes heat out of the intake charge. Thus, using an intercooler with a thinner core but a larger fontal area would be more efficient than a thicker intercooler with a smaller frontal area.

Fourthly, you can also improve the cooling efficiency of your intercooler by fitting a duct to the frontal area to force ambient air through the core. Without a duct, approximately 25% of the ambient air will pass through the core and the rest will follow the path of least resistance around the core. With a more efficient intercooler, you can increase boost pressure to offset the loss of pressure caused by the intercooler.

Black smoke (soot like) – Running Rich (too much fuel, not enough air).

Black smoke is raw gasoline burning. A rich condition can be caused by a leaky/stuck or mis-adjusted float, a choke stuck shut, a bad oxygen sensor, a bad map sensor, a bad fuel pressure regulator, a plugged up air filter, bad timing or a bad injector. Typically, if you only get black smoke first thing in the morning, it has to do with the choke or the fuel enrichment portion of your fuel injection system.

If you get black smoke all the time, get it fixed NOW. If you don’t, you run the risk of destroying the catalytic converter or worse, a rich condition causes “cylinder wash” – the oil gets washed from the cylinder walls by the fuel and causes major wear to the piston skirts & rings & bore and will lead to an engine seizure.



Blue smoke is oil burning. The tailpipe will either smoke all the time or just once when cold. If you get blue smoke all the time it is a sign of impeding doom, ie Broken rings, worn out rings, bad pistons, piston rings “glued” by burnt oil & carbon, damaged cylinder walls, glazed bores – all high dollar items.

Please note – some synthetic oils burn white.

Blowby – Remove oil cap while engine is running, if blue/gray/white smoke is seen it is a major ring/piston problem.



Smoke appears when:

1) On starting – Valve Seals (allowing oil to travel down guides into combustion chamber)

wait until you begin to see other symptoms of this oil usage or you start fouling plugs, wait until the oil consumption is greater than one quart every 1,000 miles. And never assume that seals alone will totally fix this problem, if the engine has 100k plus it’s an indication of overall wear.

2) When accelerating – Worn rings (Perform compression test)

3) When engine is de-accelerated – Worn Valve Guides



On the other hand, if all you get is a puff or two when the engine is cold and never again throughout the day, then your problem is probably bad valve guides or guide seals. It will cost between $350-800 to replace the seals, $750-1,500 to replace the guides and seals, wait until you begin to see other symptoms of oil usage or start fouling plugs, the oil consumption is greater than one quart every 1,000 miles. Never assume that seals alone will totally fix this problem, esp if the engine has done 100k plus.



Grey smoke can really be black or blue. You can usually tell which it is by the smell or by matching other symptoms you have to the colour of the smoke.



White smoke (lingering) can be either the transmission shift modulator - allowing the engine to suck and burn transmission fluid.

White smoke - Can also be Synthetic Oil burning!

White smoke – Not very common, but if your brake servo is leaking, brake fluid is sucked into the intake manifold and burns white

White smoke could also be coolant or antifreeze that is either leaking, or being forced into the combustion chambers and being burned, the exhaust will look wet and have a sweet smell to it.



A bad head gasket (75% of the time), a broken head (15% of the time) or a broken cylinder wall (10% of the time) will be the reason your engine is burning coolant or antifreeze. The repairs start at $400 and go to $4,000.

Pressure test cooling system and check all plugs. The “cleanest” plug is washed clean of all ash is often the cylinder with coolant leaking into it. White smoke will become worse when coolant is full and engine is at normal operating temperature.

Check for combustion by products in coolant.

Pressure test cooling system and inspect for coolant leaking into cylinder.



White smoke (dissolving) – Steam, cold ambient Temperature, Humidity? Disappears as the engine is driven..Nothing to worry about.



Using Oil

Slow oil consumption (no smoke) – Worn oil control rings



Engine Compression Test

Check cylinder compression in all cylinders.

Warm engine up, Remove all plugs, Disable fuel system and ground or disable ignition system, block throttle plates/pedal open.

Install pressure gauge.

Crank engine at least 3 times per cylinder and check reading on pressure gauge.



If two adjoining cylinders are low, it could be a blown adjoining head gasket.

If one cylinder is low, perform a wet test.

If compression test shows high compression on all cylinders, it is due to carbon build up

If compression test shows low compression on all cylinders it's possibly due to incorrect valve timing (jumped time)



Wet Test –

Add 2 squirts of oil to the low cylinder

If cylinder readings increase on wet-test, its worn rings, if not, its either the intake or exhaust valve seating (or in rare cases a hole in the piston). Perform combustion leak testing.



Combustion leak testing

Bring cylinder to TDC

Install leak tester

have someone hold the engine (johnson bar and 3/4 socket @ the crank pully) while you pressurize it or it will just spin backwards and possibly jump time.

pressurize

Listen for leak



If air is heard coming out of the header/tail pipe, it is an exhaust valve-sealing problem (seating problem)

If air is heard coming out of the throttle plates, it is an intake valve-sealing problem

If air is heard out of the dipstick or the oil cap, its rings or a bad piston

If bubbles come out of radiator, it’s a blown head gasket.



Engine Makes Noise

(Step 1) Check oil level and condition. If oil looks old or poor (black/white) change oil and filter with correct type. If oil is “too full” and “milky” the head gasket has failed and coolant is mixing with the oil.



(Step 2) Figure out, when and where the engine noise happens.

If noise happiness when engine is:



Drive/Neutral – Engine may not be the problem, transmission, or flexplate or clutch may be issue.



Cold/Warm Engine - No Load - High RPM (2000)

A piston (wrist) pin knock. Loose piston pins will generally knock louder when the engine is not operating under a load. A piston pin knock is sometimes mistaken for a connecting rod knock although the pin knock is not as loud.



Cold/Warm Engine - No Load - Higher RPM (3000-4000)

The connecting rod knock is caused by excessive clearance between the connecting rod bearing inserts and the bearing surface of the crankshaft. It makes a loud, sharp knock while the engine is running at a constant speed without a load. You can detect the faulty connecting rod bearing by disconnecting and connecting the spark plug leads one at a time. When you disconnect the lead from the cylinder with the loose rod bearing, the knock will go away or at least change a great deal.



Cold/Warm Engine - No Load - Low RPM (Idle)

Loose main bearings on the crankshaft cause a heavy, dull, thud type noise which is usually worse with the engine loaded. Loose connecting rod bearings or main bearings will usually cause low oil pressure. This low pressure will be more noticeable at slow engine speeds. This is because the oil pressure leaks off past the loose bearing, and at slow engine speeds, the oil pump turns too slow to pump enough oil to maintain the proper pressure. At higher speeds, enough oil is pumped to overcome the leak and build up the oil pressure. If we have a sharp knock or a dull thud sound and the oil pressure is low, the connecting rods or main bearings are worn.



Noise when Cold - Then Goes Away Once Warm

A piston slap usually sounds off only when the engine is on a pull. Like the connecting rod, disconnecting the spark plug wire to the affected cylinder will generally stop the knock. Pistons have been known to knock quite loud when the engine is cold, then the noise completely disappears after the engine warms up. Also the water pump, oil pump, idler and tensioner can sometimes make light clicking sounds on startup and dissappear when warm, only way to find it is to get the cambelt off and check each one.

A loud screaming sound which goes away can be either the alternator bearings or water pump bearings.



Location

Top of engine – Valve Train Noise, Camshaft, Valves, Lifters, Springs, Rocker Arms

Lower end of engine – Connecting Rods – Main Bearings

Front/side of engine – Timing Belt rollers, distributor, water pump or oil pump



Perform Oil Pressure Test

Install Oil Pressure Gauge.

Warm Up Engine.

Run Engine at 2000 RPM – Oil pressure should be about 25-30 PSI or more is OK.



If oil pressure is low –

Weak oil pump

Worn Main or Bigend Bearings

Damaged Camshaft caps

Clogged Oil Pickup (screen)

Low oil

Head gasket leaking - blue smoke, 1 plug clogged

Wrong Oil (too thin)

Stuck OPEN oil pressure relief valve (weak or broken)

Aerated oil (bubbles/whipping)

Oil leak (internal or external)



If oil pressure is too high -

Stuck oil pressure relief valve

Wrong Oil (too thick)



Engine Runs Rough (constantly missing cylinder)



Perform Power Balance Test to determine the dead cylinder

Once dead cylinder has been identified, inspect fuel injector and spark plug and wire to cylinder.

If both fuel and injector seem good, perform a compression test.

If plug is fouled with oil, the cylinder has a major oil consumption problem (rings or damaged piston)

If plug is washed clean it is a head gasket leak.