I'm building my own exhause and am wondering if muffler placement affacts performance? For example, will having the muffler where the cat was located and an exit at the rear of the car as normal perform differently than the same muffler places past the rear axle?

 

No effect. With long tube headers, you can get a "torque tube" effect by having the mufflers no closer than what the length of a torque tube would be for your engine (good reason not to use header mufflers). With shorties or stock manifolds, you're long past that with a muffler in the cat location. No difference either having "straight" pipe from the cat inlet location back to the stock muffler location.

 

Thanks for the reply. I'm still undecided whether to go for a single in/out in the location of the cat splitting to 2 exits once past the axle or a cross flow muffler after the axle.

 

I've about talked myself in to taking off the crossflow and putting a single in/single out in its place. I haven't seen any "real" numbers, but the word is crossflows hurt flow.