When discussing the air intake system, we mentioned that the 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
- Install a cold air induction kit.
We discussed cold air induction systems in our section on air intake systems so I won't be repeating that here, but I will look at wrapping the exhaust and powder coating the exhaust. That's not to say you can't powder coat and wrap the exhaust!
Powder coating is also referred to as ceramic coating was developed to protect space crafts 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 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 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 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!