Exhaust Systems
The main purpose of an exhaust system is undoubtedly to route the spent exhaust gas out of the car's engine. Along the way the exhaust gasses may be used to drive a turbocharger and now-a-days it will most definitely incorporate a catalyst converter to reduce carbon dioxide emissions. But on a high performance car, such as a modified street car, or a modified race car, the exhaust system is much more important as it has a direct affect on engine performance and engine power. As a result, the exhaust system, and particularly the exhaust header design, plays an important part in both engine tuning and car tuning.
In general terms, an exhaust system consists of an exhaust manifold (which is sometimes called an exhaust header), a front pipe, a catalyst converter, a main muffler or silencer, and a tail pipe with an exhaust tip. In terms of tuning the exhaust system, the muffler is the easiest to deal with it's simply a matter of replacing the stock muffler with a free-flow or high performance muffler, such as a Flowmaster muffler. The result is a free flow exhaust system. However, the performance muffler must have an inlet and an outlet pipe that is the same size (diameter) as your front pipe and your tail pipe. Your front pipe and your tail pipe should also have the same diameter. The rest of the exhaust system is much more complicated as you need consider back pressure, your engine's power band, and your engine's maximum usable RPM.
The amount of back pressure produced by the exhaust system is crucial as too much back pressure will have a negative effect on your engine's top-end performance as it will restrict the flow rate of the exhaust gasses at high RPM. The result would be the engine not being able to expel the spent exhaust gasses fast enough to prevent spent exhaust gasses from contaminating the fresh air/fuel mixture that is drawn into the engine on the next intake stroke. Ultimately, this will result in reduced engine power! Therefore, attaching a little 1-inch pea-shooter to your engine instead of an exhaust system is not such a good idea! But then neither is fitting a 10-inch sewage pipe. If the exhaust pipe is too large, you will get reduced flow velocity of the exhaust gasses. The flow velocity of the exhaust gasses assists with the scavenging of the spent exhaust gasses as well as the amount of air/fuel mixture that can be drawn into the combustion chamber on the next intake stroke. This is because the flow velocity of the exhaust creates a low pressure immediately behind it that sucks more gasses out of the combustion chamber. The trick is thus to get the back pressure just right.
Exhaust wrap like bandage and is much easier to apply than powder coating. However, if you soak the exhaust wrap in water, squeeze out the excess water, and apply the wrap while it's still wet, you will be able to apply the wrap tighter and neater. You will need a few metal ties to hold the wrap in position and it is easier to start at the port end of the header. When you apply the wrap, make sure that the overlap is constantly half the width of the exhaust wrap and be careful not to have too many layers at the collectors. You also need enough wrap to cover the down pipe but the rest of the exhaust doesn't need to be wrapped.
Powder coating is also referred to as ceramic coating was developed to protect spacecrafts on re-entry into the earth's atmosphere. It is a ceramic compound that can be applied to most surfaces that must withstand high temperatures of up to 2,000°F and can be applied to piston tops, combustion chambers and valve faces! The reason for this is because ceramic is a very poor conductor of heat. However, applying the powder coating may be a bit of a problem as you need to cure the ceramic coating in a powder coating oven at 500 to 700°F for the ceramic compound to bond with the metal surface. If you do have the required powder coating equipment, you can do this yourself.
Once you applied the wrap to the header and down pipe, leave it in the sun to dry; then spray the wrap with silicone based spray to protect it from moisture and oil. Once that's done, you can expect about 60% less heat soak in the engine compartment! Some people claim that coating or wrapping the exhaust will not affect the exhaust itself. That's not entirely true. Powder coating or wrapping the exhaust will reduce its longevity but the exhaust header should still last at least 30 years! And this applies to both powder coating and wrapping! But ultimately, neither powder coating nor wrapping the exhaust beats a good cold air induction system at keeping the temperature of the intake air down!
