# 3 Inch Exhaust?



## DerekH (Sep 4, 2010)

Just wondering if anyone has done it on NA. How were the gains? My guess that 3 inch on NA would be far too little back pressure. I want to do an exhaust soon and I'm trying to decide between going for 3 inch or just sticking to 2.5. Also i have the EJ header setup with a cat, if that makes a difference to your input.

Thanks
Derek


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## thygreyt (Jun 7, 2009)

I have had 2 different exhaust, asides front factory.

One was2.75 and the other 2.05
I did a sort of dyno for comparative reasons...

Anyways, the 2.75 had less low end torque, but better mid power (hp), it would peak at 4500 rpm, and from there, it would all just go downhill up to 6500 rpm (end of test)

With the 2.5:
It has better low end, it peaks at 6500, its a more linear dyno, and the peak its about 5-8 hp higher.


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## DerekH (Sep 4, 2010)

Thanks thygreyt, that's the kind of info i was looking for. And more or less what i was expecting.

Any more info would be appreciated. But 2.5 looks like the way to go.


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## DerekH (Sep 4, 2010)

So, today i got a custom 2.5in straight pipe made. Ive definitely lost power. Gonna have to add some restriction to it. Sounds amazing at reasonable throttle but as soon as you go to WOT its ridiculous.


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## gl_volks (Sep 19, 2011)

I also recently put a 2.5" exhaust on, one Borla "S-type" muffler. Can"t honestly say there's a huge power difference, there may be but it's not noticeable. I'll be putting in another muffler because with just one as you say, accelerating and WOT are just ridiculous and distasteful.


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## jaja123 (Jan 17, 2011)

I never would expect anything from a catback anyways. A high flow cat with a tune then yes.


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## DerekH (Sep 4, 2010)

jaja123 said:


> I never would expect anything from a catback anyways. A high flow cat with a tune then yes.


I already have a header and high flow cat.


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## KyleLaughs (Mar 23, 2010)

i noticed C2 has a 3 inch test pipe for $99, no mention of it being turbod. anyone know of this?


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## DerekH (Sep 4, 2010)

Yeah, its for their turbo setup.


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## halbwissen (Jul 20, 2001)

I have 2.5" all the way back, exhaust manifold down..
Any larger then this would be excessive, I think.


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## nothing-leaves-stock (Mar 1, 2005)

2.5'' for ANY NA is fine and more then enough.
2.5'' or 3'' for turbo
3'' test pipe is for turbo
3'' will lose power and torque on a NA car.


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