Exhaust Choice

The biggest enemy to power in a turbo charged engine is back pressure, the less the back pressure the better the turbo will be able to breath and hence the more power it will deliver. For a NA engine the size of the exhaust plays a huge critical part in exhaust gases scavenging and having back pressure in the exhaust is important.

However with a turbo charged engine it is different story. The first part of your exhaust straight after the exhaust manifold is the turbo, which creates a huge restriction in the exhaust. What a turbo charged engine benefits from is as big exhaust as possible within the allowed space. Obviously you get to a point were no matter how big you go will not yield anymore power.

The engine capacity and turbo size play a huge part in deciding the size of the exhaust. For the standard evo engine and turbo 3inch is probably the best choice for up to 450-500bhp. HKS run 500bhp on their cars with a 3 inch exhaust. A recent test conducted on a rolling road showed that there was no difference between 3 and 3.5inch exhaust. Two evo 8 MR were tested both same spec but with different exhausts. Both cars made exactly the same power.

The Evo 7-8 and the Evo260 come with a 9.8T housing on the turbo, this is effectively your first restriction on the exhaust and will limit the power considerably. So the first port of call will be to change it to the 10.5t from the evo5-6 or 8MR.

I would also recommend upgrading the down pipe with a downpipe that incorporates a high flow turbo elbow, Evo400 has developed this excellent modular design that replaces the downpipe and the elbow in one go. This also separates the gases from the wastegate and the turbine thus minimizing exhaust turbulence and increasing the flow. This design also benefit from a quick release V-clamp for future down pipe and exhaust upgrades. For price click here or fill in the contact page.