I'm looking into getting my exhaust set up for my jrsc and what I had in mind was a kamikaze header with a 2.5" downpipe and greddy sp2 exhaust. Is it stupid to have a 2.5" inch downpipe with smaller exhaust piping? I have looked for a cat-back exhaust with 2.5" piping so I could have the same diameter the whole way through but it seems my only choice is custom piping and I don't want to do that. Plus I am a little worried about the noise, so that is why I was looking into the sp2. also, does anyone have an opinion about what I shoudl do with my exhaust? i have done a lot of research on this, but i haven't found anything about my particular question. any help would be appriciated. thanks

 

Yeah, what you'd essentially do is bottleneck the exhaust gases, which isn't the most efficient way of expelling them. If you have to have different sized piping, it would be better to go from small>large than large>small. Custom piping actually isn't that bad. The only difficult part about it is finding a shop that can provide the mandrel bends (or has the machine to do it) or the labor if you know how to weld. So with that route, you can use 2.5" exhaust piping with a 2.5" muffler of your choice. For noise, have the guy weld in a resonator (or two ) to keep it subdued and quiet. I'm trying to think of a cat-back that provides 2.5" piping but am drawing a blank. Just thought of something ... see if KTeller can fab up a 2.5" cat-back. He has a good rep on here; the only thing is that you would still need a shop to weld it together, but KTeller provides all of the pre-bent piping.