Originally Posted by The Alchemist

For exhaust to be efficient, it needs to maintain velocity till it exits to the atmosphere. Although backpressure isn't good because it slows down exhaust flow, but the same can happen if the exhaust size is too large and too long before exiting to atmosphere.

Originally Posted by mdacton

do you know how much h.p. a 3" pipe supports?

I think your wasting your time and money