well my buddy said his 5 inch ex was to loud on his 03 so he went down to a 4 in and left me with the 5 inch i would like to put it on my 96 but i heard 5 right off the turbo will give me less hp i know the down pipe wont work but i have 5 lincoln welders in my shop so i know i can fab some thing up of should i make it run 4 down to 5 or scrap the idea and just run 4 i am also looking for the best efficiently

 

The "loss" in HP would not be huge for the 5" system, especially for the price of the system. You could try it and see.

 

There will be no loss of any kind. You require velocity to create a negative pressure wave behind each pulse in the exhaust system of a naturally aspirated engine to help with scavenging the pulses behind it. Throw this out with a turbocharged engine. You may not be using the extra diameter, but you certainly will not see a loss of any kind, what-so-ever.

 

There has been dyno testing on this subject to contrary that. The flow (at low volumes) in the 5" system become turbulent and do not maintain a streamline flow profile through the pipe. This increased the pressure loss "friction" through the system. Once you crest the 4000 RPM 800hp range, the exhaust volume is high enough to maintain the streamline flow.

The flow velocity through the 4" pipe provides steady streamline flow for the volumes of most of the engines. Again the loss would be minimal.