I have been talking with a guy who makes cutouts. We put one onto a WRX STi with around 400hp. He dynoed open and closed. The hp was very minimal, but the sound is killer. His cutout is just after the header. The biggest gaines are on open highway with the cutout open. His mpg went up. I posted the link to the cutouts below.

http://www.badlanzhpe.com/page10.html



WRX STi

 

Isnt this just the same as Randy's exhaust (philosphically)?

 

I believe so, but Randys exaisht is also specifiaclly designed to hold optimum back pressure while open, is bypassed after the CAT so your MINI stays in closed loop mode, and comes with a muffler that is very quiet when closed and still shows major HP improvements over stock. This just dumps air out, for a noise factor, without helping HP much.

 

Yeah it's pretty much the same thing in application. Except a cutout or what that guy is trying to do (I think) is to maximize turbo performance by dumping exhaust in a different location (closer to turbo), and having it switch between that and regular exhaust location in the rear. Turbos don't like exhaust systems, and best type is just to dump it as soon as you can, so makes sense having it dump right after the header.

Could be useful in a twincharge/turbo vehicle.