3inches or 2.5inches???;)

[jc1993]

Originally Posted by transition

Not necessarily true. http://blog.perrinperformance.com/3-...ults-and-tune/

Thanks for the link but would like to see more from other 3inch exhaust set ups

[jc1993]

i hear 2.5 has more back pressure build up and is great for n/a. anyone know if it's true???

[jc1993]

Originally Posted by Kostamojen

IF the header collector was 3" and a 3" over pipe and front pipe were included... then maybe I would agree.

But for just a catback or an exhaust that still has a bunch of restrictions, then no, just stick with 2.5".

I'm also guessing folks with the 3" have more scraping issues with the pipe goiing under the rear subframe..

i have ofheaders which i think are 3". So what u are saying is to go with 3 of i have 3" headers??

[jc1993]

Originally Posted by glamcem

Do you have an unbiased, third party dyno results..bigger is not always better ~3-5 whp or wtq difference may occur between pulls, 3" exhaust for NA cars (even for many FI is pointless)

Most of the time 3" becomes necessary at around 400whp levels and I highly doubt third party dyno results show otherwise

This has been debated for years and some people claim too large of an exhaust (for SC not for a turbo application of course) even hurts the low end torque.

Also some superchargers such as Rotrex kits -in general- makes a lot more power up top and lacks some low end power -as opposed to positive displacement SC s- I always thought it would be more beneficial to keep the low end TQ in expense to lose some top end (after 7200 rpm !!) and of course if it makes any difference

makes sense!

[wootwoot]

The difference in power will be minimal....Unnoticeable really. The difference in sound will be resounding. If it's a full race car, 3" will be good. If its a street car you want 2.5".

Honestly, if you could hear a 3" set up in person you would never question buying it. It will make you lose your sanity.

[ecdhunt]

I'm running the 3" Perrin resonated. I love the deeper tone. Not too loud at all. Makes a nice drive through twisty roads very pleasing to the ear. No need for a radio. Not sure it makes more or less power than the 2.5", but I felt the 2.5" was a bit too tame. It's not insane though - maybe just a touch louder than my BMW M Sport factory exhaust. I'd think on the Left Coast you'd have good many 86'ers near to hear some options already installed.

[1ofaKind]

I believe 3" has proven to make a bit more power over the 2.5 inch by perrin. But no all 3"inch will gain you power you have to consider the design going into it as well. It could sound like crap maybe decent. 2.5 inch is good enough but if your going for a full n/a or force induction might as well pick up a 3'inch set up of your choice.

[BlueDubbinTDI]

3" = drone

2.5" = less drone

[glamcem]

Originally Posted by transition

I have no independent tests although I trust Perrin is one of the more reputable shops. I understand that most manufacturers claims are usually optimistic though.

I also trust Perrin's quality and have been using their products for a long time what I am saying is 3-5 whp is o minimal and that much of a difference can be seen between pulls ( couple degrees colder ambient temps, car's Ecu adapting to new exhaust, car is a bit colder ..etc)..

Also, most of the time when a new part installed on the car (CAI, exhaust etc) it takes some time Ecu to adapt and when it does the difference becomes non-existent. I think best way to tell if an aftermarket part does anything is to tune with the stock part then tune with the new part and compare the results so that we can see if it yields any gains.