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Thread: need to know about FI? look here

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    Default need to know about FI? look here

    this has been compiled over the years by several members of numerous sites, i cant even remember them all now but they put together alot of great info for others to help them out. if they happen to pass thru and want credit by all means its theirs, im just speading the wealth of knowledge that they have.

    Basic stuff on how your motor works (timing)

    First thing
    Yes, you can boost your stock car! 6-7 Psi is usually "safe" and still get lots of power. Some people have been running 10 PSI daily on there motor.

    Our motor is very strong and can take a lot. If set up and tuned. I will get into this later.

    You might be asking "Where do I find parts?"

    Are the place's that carry a lot of stuff for our cars. The 3800 Series II you may have seen in some Front wheel drive cars, including the Super charged ones, Are for the most part the same short block. After that there are differences.

    Don’t buy a gasket kit for a front wheel drive car. There intake ports are different then ours.

    The heads use the same head gasket but the heads are not the same. Our fuel injectors are in our upper intake, FWD cars are in the heads.

    Nothing swaps over from the cars, not even the supercharger, it will not fit!!

    What Upgrades do I need to boost my car?"

    Not as much as you might think. Linxs (pat) Member of the board has stock motor with a custom turbo kit on it and he has put down a best of 416 RWHP (rear wheel horse power) with an open Exhaust.Of course this took alot of tuning hours.

    Since the 2 forms of forced induction for our motor are Supercharger and turbo chargers they take the place of needing a cold air intake...... or at least non of the intakes will work with them. So the only thing that's absolute necessary is spark plugs and PCV plug mod. You must get a plug that’s 1 or 2 heat range's colder (see for more info) this helps stop Pre-ignition.

    Basic info about plugs


    Ignition of the air/fuel mixture prior to its timed ignition by a spark from the spark plug is referred to as "pre-ignition". This can be caused by a hot spot in the combustion chamber, improper timing, too hot a spark plug, low octane fuel, too lean an air/fuel mixture, or engine overeating.

    Throttle body by-pass this explains why it is needed and 2 ways to do it...

    Now everything else will let your stock motor breath more which means it’s making more power

    If you car is a 1995-1999 your stock exhaust manifolds are crappy and don't flow well. Plus it's really hard to change the plugs. You can upgrade these with 2000+ years witch flow better and make plug changing a lot easier. Or buy headers
    3 place's make headers
    Pacesetters (found at many links above)

    Finally upgrade your exhaust.
    Exhaust can be found at almost every link above. I could go on day's trying to explain each one, and find what one is better then other. But it really matters on how much money you have and what kind of sound your looking for..... But anything is better then stock.

    Upgrade CAT converter.
    Federal laws regulate this so be careful. You can get a high flow cat from almost any place. Most people seem to like the "Car sound" one. It’s cheap, and flows well.

    You do not need to upgrade any internal motor parts. If you do it gets expensive really fast! Unless you’re trying to push the limits there is really no need.

    Heads an cam can be replaced without removing the motor from the car

    pistons and bottom end
    many of the place's i listed above carry stronger parts you need to do this, also you must remove the motor and have all kinds of machine done to it. this is not cheap. know one yet ahs broken our crank shaft. do to raw power

    Tuning is just getting going for these motors, there are 2 options. (1997-up cars only)(1996 cars can put a 1997 PCM in there car plug and play)
    Digital Horse Power

    How much can my 3.4 or 3.8 handle?
    The truth is to nobody actually knows, to my knowledge and many others on this board and other boards no one has broken a 3.4 or 3.8 because of raw power output.
    Usually failure is do to pre-ignition, leaning out (to little fuel) or bad tuning.

    Tuning now is getting easier and fuel upgrades are there.

    Knock can be controlled with tuning, fuel, and just not getting stupid with the boost. Also P/P the heads can help prevent hot spots that also cause knock

    Many people have been running 8-10 Psi for a while now and being smart about it is why there car is still in one piece.

    Still 7 PSI seems to be the going rate for a everyday car and 10 psi at the track.

    I don't want to go crazy but I would like a little more power from my FI car."
    The cheapest things for this are
    Changing out rocker arms for a little more lift.
    P/p heads
    P/p upper and lower intakes

    You can upgrade the cam with out removing the heads. Most people opp for this, the cam is like your lungs it controls how air flows in the motor.

    This will add power but to get max power you will need to p/p the heads to compliment the cam. Allowing the air to flow "faster" less restricted also the "port" makes more area so more air can flow. More air in/out = more power.

    IMO it’s smarter to replace the cam and heads at the same time or you'll be doing work over again. Costing you more in the end. Also if you pick the right valve-train you can rev the motor higher with tuning.

    Forced induction: Written by HAZ-Matt

    This is my take on the matter. First I would like to say "Dammit Jim! I'm a doctor, not a mechanic!" (Well, not a doctor yet but you get the idea). However, I am a scientist and I feel that my description is accurate. I wrote this because I felt that the above guide got some of the major points correct, but misstated some of the other concepts (no offense meant to T-Punk). I also added descriptions of the different classes of compressors because I feel that is very important to understanding FI. If anyone has a grievance with my guide, let me know.

    The HAZ-Matt Guide to


    The centrifugal supercharger is the only type of after market supercharger that has been fitted to a 4th Gen F-body at the time of this writing. As they are not mounted on top of the intake manifold (as any of the positive displacement type blowers are) they are easier to retrofit to vehicles that started their lives NA. It would not be economically feasible to adapt an M90 roots supercharger from a GTP to a 4th Gen F-body. If you are not satisfied by that statement, do a search or build the kit yourself.

    By the way, a turbo (aka turbosupercharger, aka turbocharger) is a form of supercharger that is driven by exhaust gases. It is technically a subtype of superchargers because the defining feature of a supercharger is that it compresses air. The method of driving the compressor is irrelevant to the definition.

    Roots Compressor

    One of the earliest compressor designs. It essentially consists of a series of rotating lobes on a set of rotors within a housing. Early designs had fewer lobes that were cut straight making them noisy and relatively inefficient. Modern roots blowers have the lobes twisted axially and have tighter tolerances and better housing designs. Efficiency has been improved greatly. While the roots blower is simplistic, reliable, and can build boost off idle, it is still somewhat hampered by the inherent inefficiency of the compressor design and by the fact that the bulky nature of the unit precludes adaptation into cramped engine bays.

    Lysholm (aka Screw) Compressor

    The screw has all of the pros of a roots compressor with efficiency as good as or greater than that of a centrifugal design. Screw compressors are internally similar to a roots compressor except that each rotor has an extra lobes, and the lobes are not ground in the same way. The lobe design allows near interlocking of the lobes which increases thermal efficiency. They also have better high boost characteristics than a basic roots type compressor.

    Centrifugal Compressors

    These simplistically consist of a “fan” (vaned wheel) inside a scroll type housing. The compressor sucks air in and the vanes push the air to the outside edges of the scroll, causing pressurization. This design relies on “centrifugal force” to compress the air (the author is aware that technically centrifugal force is not a real force, but that’s how this compressor got its name). Because centrifugal compressors are not positive displacement, they do not have good compression characteristics at low speeds, and must reach high speeds for any significant compression to occur. At high RPMs, however, this compressor type is very efficient. Crank driven centrifugal superchargers generally are internally geared to operate the wheel in the 10K RPM range, whereas turbochargers may operate at over 100K RPMs.


    Turbochargers are simply exhaust driven centrifugal superchargers. The compressor is directly linked to a turbine that is placed within the exhaust system. The compressor section of a turbo is generally smaller than the compressor of its cousin the crank driven centrifugal supercharger because it is going to spin at 10 times the RPM. The turbine looks like the compressor section of the turbo, except that the flow path is reversed and energy is taken out of the high kinetic energy exhaust gases in order that energy may be put into the intake charge (via compression). It is the turbine (in conjunction with the wastegate) that allows a turbo to function at many different RPMs at a single of engine speed. This allows greater tunability as compared to a crank driven supercharger.


    As alluded to before, the wastegate is a system that can limit turbine RPM of a turbo. In a sense, a turbo is a positive feedback system. As the turbo creates more boost, it also creates more exhaust flow. If unchecked, the turbo would spin up to some ungodly RPM and something would eventually break. It is the wastegate’s job to limit flow through the turbine and thus control turbo RPM. In the simple case, the gate is controlled by manifold pressure. When the pressure is great enough (how great depends on the spring used in the wastegate) the gate opens and some of the exhaust gases bypass the turbine. Boost controllers generally manipulate the amount of manifold pressure the wastegate “sees” and fools it into thinking the manifold pressure is less than it actually is.

    Blow off valves

    The job of a blow off valve is to limit boost spikes and vent excess boost in the case that the wastegate is not doing its job. In a completely closed intake system, when the throttle plate closes during boost (as during a shift) a pressure wave would travel backwards to the compressor of the turbo (or supercharger theoretically) and cause a decelerative force on the compressor. Minimally, this would reduce compressor RPM and decrease performance after the shift, or in the worse case it could damage the turbo. A blow off valve, like a wastegate, samples manifold pressure. When the manifold pressure is less than the pressure in the intake piping, the valve opens and the pressure in the intake is reduced.

    A bypass valve is like a blow off valve except that instead of venting the excess intake pressure to atmosphere, it pipes it back to before the compressor.


    All this air compression will cause the temperature of intake charge to increase (i.e. can’t beat thermodynamics). Intercoolers are an attempt to bring the temperature of the air closer to ambient. Lower temperature air decreases the chance of detonation and also results in a higher flow rate through the engine. Flow rate is proportional to power output. Intercoolers received their name because some piston engine era warplanes utilized twin stage superchargers in order to maintain engine power at high altitudes. Even though many of those aircraft ran on 160 octane leaded fuel, heating of the intake air was a concern (see Rolls Royce Merlin engine design). A device, essentially a radiator, was placed between the first and second supercharger stages, and the “intercooler” was born. A similar device could also be placed after the second stage and was called the “aftercooler.” Although technically what we see on the automobiles today are more directly related to aftercoolers (some supercharger kits refer to them in this way) apparently intercooler sounds ‘cooler’ (pardon the pun) and that is what description we commonly use for these little radiators.

    The two main types of intercoolers are the air-to-air and air-to-water types; the main difference is which medium accepts heat from the intake charge.

    Air-to-air intercoolers exchange heat between the intake charge and the ambient air. Efficiency is commonly in the neighborhood of 80%. Air-to-air intercoolers must be placed in a location with sufficient airflow or they will not be able to effectively exchange heat. Two subclasses of air-to-air intercoolers are the cheaper tube and fin design, and the more robust and efficient bar and plate design. The main advantage of an air-to-air intercooler is simplicity of design.

    Air-to-water intercoolers may operate at efficiencies greater than 100% if the water is at a temperature below ambient. These systems do not need to be placed in the path of airflow, so there is some freedom in choosing a location for it within the vehicle. The actual intercooler portion of the system is generally smaller than a comparable air-to-air intercooler. Unfortunately, air-to-water systems are more complex in that they need a coolant reservoir and some method to extract heat from the coolant.


    In simplistic terms, the engine functions as an air pump. The more air and fuel that is pumped through, the more power you can make. In order to pump the air, pressure on the intake side must be higher relative to pressure going out the exhaust. In a naturally aspirated engine, valve timing events are used to create a pressure. Since you are reading this guide, you are probably not interested in naturally aspirated engines, so we can leave it at that. That said, we can all agree that it makes no sense to build a naturally aspirated performance engine. From a performance standpoint, it would generally make sense to use some means to pressurize the intake, while using some means to decrease the pressure in the exhaust path. The second part is easy; almost everyone and their brother has some type of exhaust work. The first job is a little trickier. Fortunately we have superchargers (and turbos) to save the day.

    A crank driven supercharger will most definitely increase the pressure on the intake side of the engine. Since it is limited to the intake track, it will not adversely affect the pressure in the exhaust. The pressure on the intake side should always be greater than the pressure in the exhaust. However, power doesn’t come free, and you must use some of that newfound torque to spin the supercharger. How much that takes is calculable, but is purely academic because significant power is netted. In the case of positive displacement superchargers, boost can be had at very low RPMs, and in the case of the centrifugal and screw supercharger, good efficiency can be had. Other reasons to choose a supercharger are that the retrofit to an NA car should be smoother because there are no changes to be made to the exhaust path. The power curve is predictable because boost is largely dependent on RPM of the motor and not some less tangible factor such as engine load.

    Now why would anyone want a turbo? Turbo systems are more complex because they require revision to the intake and exhaust sides of the motor. From the air pump standpoint, at first glance they seem to be inferior to a supercharger as you are placing a restriction in the exhaust flow path (i.e. the turbine). And given what we know of centrifugal compressor efficiency at low RPMs, there may be a significant portion of the rev range before the turbo will reach threshold and begin to create boost (this is what “lag” is). However the relative independence from engine RPM is the turbo’s greatest advantage over any other supercharger type. Boost can be reset with ease, and therefore tunability is also greatly increased as compared to a crank driven unit. While the adiabatic efficiency of the compressor may not be as great as that of a screw type supercharger, the drive mechanism is much more efficient, as a turbo relies on utilization of largely wasted kinetic energy in the exhaust gases. All of this combines to form a versatile, tunable unit that has the potential to make more power than a crank driven supercharger.

    So a turbo must be superior to a crank driven supercharger, right? If that was the case the crank driven supercharger would have died out long ago. For all out power the turbo reigns supreme, but life unfortunately is full of compromises. Packaging is a huge concern during a retrofit of forced induction onto an NA motor, and in that instance the crank driven supercharger has the turbo beat handily. The user must decide on his or her priorities and decide from there.
    1995 Trans am- project procrastination
    2003 Cavalier- Because race car!

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    1995 Trans am- project procrastination
    2003 Cavalier- Because race car!

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    Water Injection
    This topic has often been mentioned in internal combustion engine publications and many SAE papers (Society of Automotive Engineering). I will do my best to explain what it is and how it can be implemented in automotive engines constructively. Please notify me of any mistakes or inaccuracies made so that I can correct them.

    Why water?

    Unlike any other liquid, water has the highest latent heat of vaporisation of all the known liquids that exist on this planet, naturally other than Mercury. Its strong inter-molecular bond is the main reason why it requires a large amount of heat energy to separate its molecules from each other. It requires 2240KJ of heat energy to fully vaporise one litre of liquid water into gas. Translating this into meaningful terms, a 3KW domestic electrical kettle will need 12 minutes or so to fully evaporate one litre of water, the equivalent energy to keep a 100W light bulb on for 6 hours.

    [/b]A contardiction in terms?

    You are now probably wondering why we are injecting water into any engine resulting only in taking heat energy (power) away since the sole purpose of a car engine is to convert air and fuel into heat energy to do the work of turning the wheels. Let us first look at the thermal dynamics of an engine – the energy produces is basically shared amongst three areas, pretty equally. One third is lost in the exhaust pipe; one third is transferred into the atmosphere via the normal cooling system. The remainder is for turning the wheels. As this document progresses, the reason for adding water injection will become more apparent.

    Aiming for a highly efficient and powerful engine set up:

    Having covered the engine basics, we can now examine how one can improve the efficiency of an engine by recovering some of the heat loss mentioned above. Engine efficiency can be greatly improved by increasing the compression ratio – the ratio that governs how much of the energy is channelled into useful power rather than just plain heat loss to the atmosphere. A normal spark ignition engine runs at an average compression ratio of between 9:1 to 10:1. The limitation here is the octane rating of fuel used, the higher the octane number the higher the compression ratio that can be used. In other words, an engine designed to run on 98-octane fuel will be more efficient and potentially produces more power than an engine designed to run on lower octane fuel. Octane rating is a measure of knock resistance – a higher knock resistance will allow an engine to run a higher compression ratio or more ignition advance hence producing more power.

    How manufacturers contribute towards it:

    Modern electronics has played a big part in allowing a normally aspirated engine to run a vast range of fuel grades by constantly adjusting the ignition timing until the knock limit is a degree or two ahead. Your engine is now getting the optimum timing ( by varying the effective compression ratio with the ignition trim) for a given grade of fuel. In order to stretch the efficiency of engine further with a given amount of air it can inhale, a turbocharger is added. The heated gas from the exhaust is harvested to power an air pump (compressor) to improve the volumetric efficiency of the engine. This arrangement will recover some of the wasted energy towards the wheels instead of being lost to the atmosphere.

    Can we do more to shift more energy towards the wheels with a turbocharger?

    Nowadays, modern electronics can further improve the power output of a Turbocharged engine by constantly modifying the boost pressure. Although a turbocharger can stretch the dynamic operation range of an ordinary engine it is still somewhat limited by the fuel grade used – over stepping this limit will result in the onset of detonation.

    Stretching the limits on a Turbocharged engine…

    The easiest way to extract more power output is by increasing the octane rating of the fuel (race fuel has that property). Any race fuel will allow you to run extra boost and extra timing thus further improving the efficiency of an engine. Unfortunately race fuel is not easily obtainable from normal commercial petrol stations. An intercooler will further improve the efficiency of a turbocharger by increasing the density of the compressed air from the turbocharger.

    Extending the limit further.

    So far we have outlined some existing methods to push the barrier further and most of the mentioned methods have already been implemented on some modern turbocharged engines. So how can the injection of water squeeze more efficiency out of a modern engine? The answer is - you can’t, unless you are prepared to increase the existing compression ratio further. In the case of a turbocharged engine, it means running a higher pressure-ratio. This is not new, car manufacturers are already using this technique such as timed over-boost during acceleration and boost tapering down over certain RPM etc. During these periods, the a/f mixture is enriched to assist in-cylinder cooling.

    Power comes with a price.

    With every modern factory turbo car produced nowadays, it is fuel-efficient until pressed hard. I have not seen any factory equipped turbo cars that doesn’t dump fuel under hard acceleration. It is not the preferred intention of the makers but they have little choice, since they have no other means to control the thermal loading within the combustion chamber. A bigger radiator or oil cooler is one answer however unfortunately the frontal area of the car doesn’t increase with the power output of the car.

    How Water Injection can take you past the final barrier…

    We have finally arrived at the main topic – water injection. So far we are seeking a way to improve the efficiency of the engine and hence how much power can be squeezed out of an existing set up and of course without using extra fuel – we call it the final barrier. We will address this particular area of the turboed engine's dynamics and sum up how water injection can contribute in different areas and the reasoning behind the claim.

    Water Injection will improve the turbo operating range:

    A turbocharger has a designed operating range defined by a chart. Its flow characteristics are selected carefully to match the engines operating characteristics by car makers. Each operation range has an efficiency boundary denoted by percentage. Ideally, one should operate within the most efficient boundary area. When boost is increased, it tends to shift the operating range outside this area. Loosing about 5% efficiency each time it is shifted further away from the ideal boundary. It doesn’t mean that it stops working altogether but the loss in efficiency almost always translated into heat. The further away the shift, the hotter the charge the air gets. Almost all modern turbo cars use intercoolers to reduce those high charge air temperatures.

    Introducing water injection will absorb any heat left over from the factory’s intercooler designed capacity when the turbocharger’s operating range is extended. High ambient and low vehicle speed will further tax the efficiency of the intercooler so having a water injection as a secondary cooling mechanism is very useful. Water does not have the problem absorbing heat as the intercooler in less-than-ideal conditions. Provided the water is well atomised and exhibits a great deal of surface area, it will grab heat very quickly. As the cooling effect is taking place, the air shrinks to accommodate more air coming out of the turbo or intercooler, resulting a extra throughput of charge air. The myth of water vapour displacing the air is sometimes over-stated – the volume of the water vapour occupied is minimal. It has to be noted that when the temperature in the inlet drops, the droplet size decreases and occupied less air space.

    Water droplets working hard in the combustion chamber.

    We have now arrived at the most important aspect of water injection in dealing with overall performance gain and fuel efficiency. Moistened air has the effect of reducing the temperatures of the surrounding engine components as it enters the combustion chamber allowing better volumetric efficiency of the induction stroke. Some cooling capacity is used during this cycle so the droplet size becomes smaller but only to the advantage of the next engine cycle. During the compression stroke, tiny water droplets are distributed amongst the charge air in the ratio of about 120:1 (based on water to fuel ratio of 10:1). This has the effect of regulating the flame speed thus promoting even flame propagation speed. The predicable burnt rate is essential for accurate ignition mapping to produce consistent power.

    Any non-homogeneous a/f mixture exhibits abrupt frame-front temperature changes, this condition promotes the onset of detonation especially towards the end burnt period. Once detonation has started, it will tend to continue for the next few cycles even the subsequent condition is normal. The most common solution adopted by most engine management to avoid this from happening is by running an over-rich mixture. This has two effects – excess fuel cools the mixture and slows down the burnt rate. Slowing down the frame speed has the effect of shifting the peak cylinder pressure curve during the power stroke. When pressure is build up further away from the top dead centre (TDC) line it will minimise the onset of detonation but in expense of loosing some pressure that feeds the pistons to tuning the wheels. Rich mixture not only wastes fuel but it forms carbon monoxide molecules, a product that has only 30% energy release of the carbon dioxide, a fully oxidised carbon molecule. Every molecule of carbon monoxide carries an oxygen molecule out of your exhaust. Keep in mind that the engine only inhales about 20% of oxygen and should be treasured.

    Continued below
    1995 Trans am- project procrastination
    2003 Cavalier- Because race car!

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    Contuned from above

    Now comes to the all-important reason why we are injecting water to rob heat energy - in order to push the power boundary further to obtain some meaningful figures, the boost pressure can be increased further (higher effective compression), aim towards MBT (maximum brake torque) timing and 12.5:1 a/f ratio. Since the use of race fuel is not on the menu. As we approach those tuning levels we will experience considerable increase in cylinder pressure and temperature, but at the same time more power. Since we cannot raise the melting point of the pistons, we must find a way to control and keep the engine components from overheating. Having six times the latent heat of fuel and huge expansion rate from liquid to gas (single molecule of water – not droplets) water is the ideal substance to inject as a coolant.Having absorbed and dealt with the destructive heat, the by-product (superheated steam at x1400 volume increase) becomes an active partner in adding force to the downward pistons. Water is converting the extra heat energy for wheel power. Without water, the excessive heat must be transferred to the cooling system and lost into the atmosphere. Since the quantity of water injected is relative small compared to injecting some six times the amount of fuel to arrive at the same cooling property. To all intent and purposes, we are not advising anyone to go this far but the possibility is there and achievable. In most cases, one can venture into the extreme gently. Since water in free, it cost nothing to continue your quest for a highly efficient engine that produce far more power than the fuel dumping method used by the makers.

    One word of warning, a water injection with good failsafe capabilities must be your first priority when you are choosing one. So how much water should be injected to be effective? For those how want to extract the maximum power and not achieving maximum economy. To date, apart from the Audi FSI and some new Honda engines, it is considered an a/f ratio of 12:5:1 a/f ratio will yield maximum power and 14.5:1 for maximum economy. The exact a/f ratio vary from engine to engine, it has a great deal to do with how homogeneous is the mixture induced. We know that under WOT, full boost conditions most turbo car’s a/f ratio drops down to 10:1 to 10:5:1. 3% water to fuel will be have the same heat-absorption properly of the excess-fuel as running from 12.5:1 to 10.1:1 a/f ratio. We normally recommend 10% of water top fuel to make it extra safe.

    Document on water injection by Richard Lamb 7th August 2005, free to be distributed in whole only with the correct reference to the author and source.
    1995 Trans am- project procrastination
    2003 Cavalier- Because race car!

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    Awesome info. 1Lo - please sticky.

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    very impressive.... sticky please!!!

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    Was already sticky'd days ago!!!!!

    "There is no shame in owning a V6. Anyone that makes fun of you is just upset that they spent more money than you, and their penis didn't get any bigger..."

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    can the throttle body bypass work on a 3rd gen 2.8l?

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