I want to make an exhaust from the downpipe back basically... I dont know what the correct size would be for a car liek this but I have access to 2.5" steel piping that I can bend to fit to the car and weld on hooks to the piping. And at the end of each Pipe I would add mufflers to add a little back pressure. Does anybody know a DIY on this or would an exhaust of this size not be smart to make? I wouldn't ave a catalytic converter either but I would be driving it around on the street. Any help/tips would be greatly appreciated thanks.

 

http://www.racingbeat.com

Check out their presilencer/downpipe setup for NA's. Its inexpensive and will get the job done and you won't have any hassles with anything not working.

Good luck!

 

I ran 2.5 on mine for a long time before I went turbo n/a it worked fine make your own it is a lot cheeper also when bending pipe try to bend as few times as possible and try to make 30 deg. bends instead of 45 deg. bends it dosent really matter how big the pipe is it if how easy will it flow and 2.5 should be great. also with a s4 your 5 and 6 ports depend on back pressure to open just wire them open and it will work fine it did on mine.