i got the gmpp cat back n cut out the cat and resinator and ran strate pipe through...am i loosin back pressure?...if so am i loosin hp??

 

back pressure is a myth. basically...

what happens is, exhaust isn't a smooth flow, like water would be, it comes in short spurts as the engine fires. so, the logic is that the correct size pipe will allow each spurt to create a small vacuum behind it and help the next out. that's called exhaust scavaging.

if the pipe is too big, it doesn't do that, it just lays in the pipe, so the logic was always that it's better to me a little too small, then too big, esp for low end power.

the simple way to look at it is, every exhaust is a compromise. noise, high end flow, low end flow. if you make a lot of flow, you'll gain up high, but loose down low.

 

You want to lose as much backpressure as you can while keeping exhaust velocity up. You aren't going to make too big of a difference in cutting out the resonator anyways, and the exhaust is going to sound pretty loud and obnoxious IMO.

 

what he said 2 up^^^^.. that is exactly how back pressure works.

 

If you look at the GMPP resinator, its a flow through design anyway. It would make no differance with it removed, except make it sound obnoxius.

 

Dont cut ur cat out please, it sounds terrible and its illegal.

 

just leave it, cutting anything out will make it too loud and sound like a ricer, especially the cat