Custom? Modded from new gens? Just catless down pipe and nice muffler?

 

What is the best diameter to run? 3" too big?

 

Let's discuss!

 

Rick

A lot of people run straight 2.5" pipe. Probably not legal in most states as it nulls any attempt at emissions. Now, offroad use is different.

 

I ran 2.25" pipe with a flowmaster, it sounded alright, but a little too muscle car for me. A lot of people will say that you don't really have a size restriction after the turbo, as the turbo is all the backpressure you need.

 

On a slight tangent: I've bell mouthed my downpipe and that made a huge difference for spool up.

I could tell you what I run (1.5" primaries, 1.75" to the turbo, 3" DP, 2.5" catless to a flowmaster American Thunder muffler) or I could point you to some information.

 

I designed part of my exhaust (the header mostly) using info from these authors. They know their stuff and I trust their opinions and advice. Read and learn:

 

http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/900/how-to-make-your-own-effective-exhaust-system.aspx

So, a 3" turbo back is not too big for the car then? Or would it be better to go sti dp, then 3" from there?

 

My idea is to run a 3" bellmouth or sti dp, and have a custom 3" built with maybe a flow master/deltaflow dp back, that way I can swap back to stock for emissions tests fairly easily....

 

I'm also going to upgrade the turbo to a vf11 from a legacy ss.

 

 

Rick

I put a 2.5 inch trubo-back on my old wagon. Only difference I noticed between that and the crappy made 3 inch that was on there is that with the 2.5, you can't hear the turbo through the tailpipe very well..