Hello.
I'm getting close to needing to design the exhaust for my car. I was originally thinking of doing a down pipe that was 3" and opened to 4" and went straight back into a single 4" ID muffler. However, I have a 3" exhaust that I had made with my stock TII. Would it be too much restriction on my setup just staying at 3" all the way back?

The turbo is a BW S366, .91 a/r
I can provide more details on the setup if needed.

Thanks

 

lots of horsepower has been made with 3" . Lots. J-rat did over 500 to the wheels with a 2.5" RB catback

 

wow, that's really impressive. I think I'll stick with the straight 3" then, doesn't make much sense to spend the money if I don't have to.

Thanks for the info!

 

Catback doesn't make a huge difference below 500rwhp. I have done back to back tests, its usually about 10rwhp @ 450-500rwhp.. Test was done on the a FD with the single tip old school RB unit...

You will have faster spool with a bigger system, those are usually the most noticeable benefits

 

would it make any difference if it was a dual exhaust? the exhaust I have is an open 3" dual, I was going to have one end of the "Y" cut off and use it to fabricate the down pipe to save a few bucks, but if it's going to affect my spool time then maybe I'll reconsider.

 

I had a NA rbexhaust and switch to a single 3 inch. and noticed better gains in spool on my t70 but never had any proof of more power.

 

3" all the way from downpipe on my car and it sounds good and makes good power