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Car Exhaust System

The car exhaust system helps to route out 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.

A car exhaust system consists of an exhaust manifold or an exhaust header, a front pipe, a catalyst converter, a main muffler or silencer and a tail pipe with an exhaust tip.

BASIC DESIGN

Generally speaking, a 2 ^1/4 inch exhaust pipe is ideal for an exhaust system for a 4-cylinder street car, but a 2^1/2 inch exhaust pipe is a better fit for a 6-cylinder street car. However, a 2000cc 4-cylinder modified race car would do much better with a 3-inch exhaust pipe! The size of the exhaust header primary pipes is also important as it influences both back pressure and flow velocity; while the length of the primary pipes affect the power band of your engine. The size and length of the primary pipes of the exhaust manifold, as well as your exhaust header design depends on the engine's displacement and maximum usable RPM, as well as the power band you want from the engine.

Exhaust Header

The exhaust manifold design, or exhaust header design has a major affect on engine performance and plays an important role in car tuning. In terms of exhaust header design, both the primary pipe diametre and primary pipe length will determine the engine's overall power band as well as its peak power point.

Tailpipe

The size of the tailpipe is also complicated by the size of the turbo and the boost pressure. Tail pipe size is also based on the bhp produced by the engine.

Exhaust System

When discussing the air intake system, air in the engine compartment can be 30 degrees higher than ambient air temperature for a normally aspirated car and 50 degrees higher for a turbocharged car! And higher air temperature is a big performance killer as it is less dense and contains less air molecules than cooler air. Most of this increase in temperature is cause by the exhaust system.

There are three things you can do to reduce the heat soak from the exhaust system:

Wrap the exhaust;
Powder coat the exhaust; or
Get cold air induction.

Powder Coating

Powder coating, also referred 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. Once applied and cured, the exhaust will radiate up to 40% less heat! Unfortunately, that's not as good as applying an exhaust wrap, though it does look much neater!

Exhaust Wrap

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. Once that's done, you can expect about 60% less heat soak in the engine compartment!

DISADVANTAGES

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!