Exhaust Piping.
 

I read the above, but I still wanted to get some opinions. This will be on a 2.0L 3SGTE turbo motor with a stock turbo pushing max say 15psi.

The exhaust I have is kinda weird here are the specs: 2.5" B-pipe then increases to 2.75" into the canister.

Now my question is would I benefit more from a 3" downpipe or 2.5"? Would the 3" DP create unwanted back pressure? Yea I know I need a new exhaust LOL. Will do when I decide to get a new turbo or something.

Thanks!

If your downpipe is 3" but flows into a B-pipe that's 2.5...then it really doesn't do anything. Might as well just stick with a 2.5" downpipe. Intuitively, you would think the flow is interrupted (turbulence) when it goes from 3 -> 2.5, and such is true. A straight 2.5 is much better.

if your piping is only 2.5 there's no reason to get a 3" DP since it'll just get bottle necked anyways, unless you're planning on getting a 3" exhaust anyway. personally i think 2.5-2.75 is perfect for your setup, i say that even though i have a 3" on my NA car lol .

I would go with a 2.5" downpipe setup.

Totally OT, but are you putting in that motor in your Prelude?

As you know the 3SGTE from the mr2 is essentially a FWD motor setup.:p

Yes I do know that and that's prolly why it should be a somewhat easy swap. :p

Go with a 3" dp it will help spool even if it bottlenecks further down the line.

This. For sure. 3" all the way back would be ideal of course...

If you have the option to do a 3" down pipe do it now rather than have to do it later. The boost gods will thank you for it.

Berz out.