2.5" exhaust VS. 3" exhaust......

[mustg5]

What kind of a difference is there between 2.5" from the turbo to the cat with a 3" catback system VS. a 3" exhaust all the way from the turbo back?

 

[floorguy724]

Correct me if I am wrong but with the staggered exhaust from 2.5 to 3 you would have better low end then a full 3" exhaust, but on the other hand I've heard that rule of thumb is to go with the biggest exhaust for turbo car for better spool up. Thank you.

Ivan

 

[mustg5]

i know bigger is better for spool up, but overall anyone know??

 

[WhiteTsiAwd]

I dont really think that 3" is needed until you reach 11's or so. If you just bolt up a 3" turbo back then you will get boost creep(if there is no cat on, granted you will still get some possibly) but if i were you just save urself the time and money of upgrading later and go ahead and get full 3".

 

[ITSME4G63]

Originally posted by WhiteTsiAwd
.If you just bolt up a 3" turbo back then you will get boost creep(if there is no cat on, granted you will still get some possibly)

Yep, 3" turbo back here, getting boostcreep at times. 2g ported e/x mani should be this weekend and i already got the ported o2 housing. Just gotta put em on.

I think the largest they make for dsms are 3.5"

 

[nine5raptor]

Some guys around here have stuck on 4" straight pipe :laugh:, but I don't know of any actual exhasts that come near that big.

 

[jbillakdsm]

RnR sells a 3.5" system, but I don't know how far you'll get down the street before the cops pull you over for noise violations. I would take a step back and evaluate what your goals are for the car and go from there. If you want a fast street car and don't intend on taking it to the strip a lot, I'd say go with a 2.5" O2 eliminator DP and 3" from the cat back.

 

[NOSNUSE]

Full 3" exhaust is good for all out horse power,RRE uses a 2.5" DP from the turbo to the flex section on there pipes, but go to 3" after that.

 

[mustg5]

i should be in the low 11's with about 450whp.......3" all the way??