First off you must come up with some sort of goal. Do you want all-around performance, an autocross machine, or a drag racer. The main ingredient in all these is money followed shortly by time and patience. When you mod your car you must know your bounds. Do not spend every penny you have, simply for the fact that it will leave you stranded if something fails or breaks apart on your car. Once you have estabolished what you want and you have the time and money to do it then you can move on to getting dirty.
Naturally Aspirated Modifications
Intake - Dont run out and buy the most expensive unit. Ask around for the best deal for the money. Cold Air units will give the best power gains but they have the added danger of water ingestion, when the air filter sucks up water, which is in-compressable, which can blow the motor. This generally wont happen unless you submerge the filter in water, like trying to drive through a large puddle. Short Ram units will simply reduce the restriction of the vehicle's intake system providing more air. Short ram systems can be made as effective as the cold-air units by getting cold air to feed to the filter. This can be done by using stock piping that ran ambient air to the stock air box or by creating your own piping, see the RAM-AIR how-to.
Header - One of the best modifications for the N/a set up is the header. The stock header is generally this ugly unit basically just designed to be a pipe for the exhaust gas to travel through. They are often very heavy and made of thick iron that rusts. By replacing the stock header with one that is made for performance you not only gain power but lose weight and get a cleaner looking engine. A performance header not only flows better than stock but actually "sucks" the gases out of the cylinders. This act is called scavenging. The design of the header also provides more power. This is done by 4:1 or 4:2:1 systems that are specifically designed to flow better and provide power where you need it most. Note, headers will make your exhaust a bit louder but are well worth the money!
Exhaust - Exhaust gains are largly dependent upon your stock system and how it flows. When you add the intake and header to your car the stock system will reduce the effectiveness of those mods simply because it is designed primarily to flow stock amounts of gas and reduce noise, and in doing so create more restriction. Aftermarket exhaust systems are cat-back systems meaning they replace the stock unit from the catalytic converter all the way to the muffler.I would suggest a 1/2" pipe increase max on a N/a set up. The larger the pipe the less low-end torque you will have but you will gain more top end hp.
Camshaft(s) - The camshaft is the first active modifications you can make. It does not reduce restriction but actually changes the mechanical timing of the valves. Duration is the amount in degrees of rotation the intake and exhaust ports are open. Lift is the lift the cam acts on the valve. Larger #s are not always better as the larger your duration and lift #s are the less low-end torque you will have. You will have an effect similar to turbo lag where you will have low power until you reach the cams effective range, or in turbo lags case, boost. For a street application you want a mild cam to boost top end power while retaining a smooth idle and a good powerband. Drag cars utilize a rough idle racing cam that is built for top end power. Autocross vehicles generally use street cams or a stage above.
Larger Throttle Body - Greater throttle response and allows more air to pass which creates more power.
Fuel Pressure Regulator - With more air entering the chambers you will need more fuel. The stock system often will produce a lean situation when intakes, cams, and throttle bodies are in play. By raising the pressure a few psi you can add more fuel to the mixture and add on power.
Porting and Polishing - Factory heads generally flow decently but when you are done with the above and want more power the head is a good place to find it. Polishing is the act of smoothing the casting burrs out of the valve openings and the head itself. Porting is the act of enlarging the valve openings for greater flow and often it encorporates the use of larger valves. It is something that you can do yourself with a little bit of knowledge and practice.
High Flow Cat - The cat, catalytic converter, is a very restrictive peice that converts greenhouse gasses into harmless water and CO2. It also converts un-burnt fuel into carbonous deposits. By getting a larger, high flow cat you can reduce back pressure and create a better flowing system, and thus more power.
Timing - You can often advance the factory timing a few degrees. By doing so you make the engine spark a few milliseconds faster causing the mixture to burn longer which will create more power. With advanced timing I would suggest using 91 octane fuel to prevent pre-ignition.
ECU upgrade - By remapping ignition sparks, timing, air/fuel ratios, and rev limiters the ECU creates more power. I would suggest holding off on this mod until you have completed most of your N/a build so that the company you get the ECU re-mapped from can re-map it based on your car's specifics.
Internal Modifications - Forged internals are more resilient and can handle alot more power. They also can be utilized in the form of a stroker kit. A stroker kit generally overbores the cylinder to give a bigger bore and the new crank extends the rods higher giving a longer stroke, thus more displacement. Stroker kits also incorporate higher compression pistons that will also create more power. Higher compression will call for higher octane!
Fuel System Upgrades - Upgrading units like the fuel pump, injectors, rails, and lines will allow you to run more fuel into the cylinder and will create more power by enrichening the a/f ratio, which burns more fuel = more power. For a turbo car a better fuel system means more boost and power is "boosted", pun intended, considerably.(yeah I know its a retarded pun)
Air/Fuel Ratio Controller - A/f controllers help you to correct your own air/fuel ratios to create more power and prevent detonation. 14.7:1 is the perfect ratio. Anything greater than 14.7:1 (ex. 17:1) is considered lean, a detonation prone condition. The higher the first # the leaner the mixture. A 15:1 mixture isnt really lean but think of it as a # on a spectrum.
Lean Rich
<--------|-------------|-|-|--------------|--------->
^ ^ ^ ^ ^
17:1 15:1 | 14:1 10:1
|
14.7:1
A mixture that is too rich or too lean will create detonation, which is bad. And will reduce engine power considerably.
Turbo/Supercharger Modifications
Turbo Timer - The first mod for any turbo car. The turbo timer allows the engine to continue running for a set amount of time after you have pulled the key out to allow oil to continue to circulate and cool the bearings in the turbo. Remember the turbo doesnt just stop when you turn off the car. This will preserve your turbo and keep it operating at peak performance.
Blow-Off Valve - When a turbo is spooled it creates pressurized air. This air is essentially "boost". Boost is good when the throttle is open cause it goes the proper way, into the intake manifold. But when you go to shift the turbo simply wont stop, its spinning at over 100,000rpm!!, so it still creates boost but this time there is a throttle plate in its way so it surges the compressor, the turbo. This slows down your turbo and stresses it, which hurts its longevity. A blow-off valve is placed on either the hot, pipe following the turbo, or cold, pipe from intercooler to manifold, pipe. At a certain pressure it will "pop" open releasing the pressure in the pipes, a reason it is called a pop-off valve. This makes the "whoosh" you hear when your friends Turbo DSM up shifts.
Exhaust - Often the stock exhaust system on a turbo car is more restrictive than the N/a systems. Restriction works like a small brake to slow spool up of the turbo which isnt fun cause it creates more turbo lag. Switching to 3+" piping with a high flow muffler will allow the turbo to spool a full 500 rpm (+/-250rpm) sooner as well as creating more top end power.
Intake - Intake works the same way as the N/a intake. It helps the turbo boost a bit faster cause you remove the restriction and will create cooler boost temps. Cold Air units are not really necessary but you could always use the "RAM-AIR" how-to to learn how you can create your own cold-air system. Intakes will often give you a louder turbo induction noise.
Boost Controller - Boost controllers allow you to control the amount of boost the car runs. It does this by electronically controlling the wastegate. Boost controllers can also provide turbo lag reduction and faster spool up times.
Intercooler - The intercooler is a radiator built for air. The fins soak up the heat and radiate it into the ambient air flowing over the fins. This cools the boosted air considerably and creates more power as a result. It also prevents detonation which will destroy your engine. Larger intercooler will cool the air faster and as a result create more power but they will increase turbo lag.
Higher Boost - Higher boost levels will create more power. Higher boost levels will tax your turbo system more so there are a few things that you must know before you go crank the boost. First thing, does your car have the proper fuel system to accomodate for all the new boost air. Then does your turbo have decent efficiency at that boost pressure?
Ex. A DSM's T-25 can only efficiently boost 14-15 psi max. A T88 boosting 14-15 psi would be way out of its efficiency range and would create extremely hot boost temps that would melt pistons. Turbonetics.com can provide compressor maps for your turbo to outline its efficiency at a certain point.
And lastly will your engine withstand the boost. Will your head gasket survive the new conditions? I would suggest that you replace the head gasket with a suitable metal gasket built for higher boost for safety. And also another common problem with raising the boost is the little hose clamps can come loose which will pop off your intercooler hose and you will lose all boost and your engine will bog.
Internal Modifications - Like the N/a units the forged parts are more resilient and can thus handle more boost and power. Pistons often have lower compression ratio as the stock pistons to aid in detonation resistence. Forged internals are a must for turbo 4 cyl. cars when you approach 400 hp. 6 Cyl. cars have proven to be very resilient, (Supras, Skylines, and VR4s), and often handle 700+ hp set ups.
ECU Upgrade - These often get most of their gain by raising stock boost levels. They also provide better timing and detonation response. Air/Fuel ratios are also corrected all over the power band.
Fuel System Upgrades - Upgrading units like the fuel pump, injectors, rails, and lines will allow you to run more fuel into the cylinder and will create more power by enrichening the a/f ratio, which burns more fuel = more power. For a turbo car a better fuel system means more boost and power is "boosted", pun intended, considerably.(yeah I know its a retarded pun)
Air/Fuel Ratio Controller - A/f controllers help you to correct your own air/fuel ratios to create more power and prevent detonation. 14.7:1 is the perfect ratio. Anything greater than 14.7:1 (ex. 17:1) is considered lean, a detonation prone condition. The higher the first # the leaner the mixture. A 15:1 mixture isnt really lean but think of it as a # on a spectrum.
Lean Rich
<--------|-------------|-|-|--------------|--------->
^ ^ ^ ^ ^
17:1 15:1 | 14:1 10:1
|
14.7:1
A mixture that is too rich or too lean will create detonation, which is bad. And will reduce engine power considerably.
Nitrous Modifications
Coming Soon
Email: Boostn_S14@yahoo.com
