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Discussion Starter · #1 ·
OK, I've read all of the articles on exhaust. I'm looking to get a full exhaust system (headers, cat, cat-back) by Christmas. I was planning on getting some Comptech 4-2-1 s/s mig welded headers, carsound cat, and GReddy EVO cat back. My whp goal is about 190whp-200whp. The GReddy EVO is 60mm piping, the right size for my goal. I want 60mm piping all the way through the exhaust (headers to muffler) right? If this is so, what are some headers that have 60mm piping? Does Carsound only have 2.25" and 2.5" cats, or do they have 60mm cats as well? If I am completely wrong in my assumptions, tell me what I should be looking for. Sorry about all the questions, I just want to make sure that I buy the right exhaust for my car. Thanks!
 

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The 2.0" stock-sized Comptech header is too small if you're going for the 200whp range. You'll probably want to step up to one of the 2.5" JDM size headers and cat. The one you choose basically depends on your budget. The least expensive in this category is the DC Sports JDM 4-1 which is pretty much a copy of the Mugen 4-1 but surprisingly performed better in the great header test. Most of the other 2.5" models can get up there in price starting at $600 going all the way up $1300.

For the exhaust I would go with a 2.5" system to make it 2.5" all the way through. If budget requires you to get a cheaper 60mm exhaust then get SMSP's step down adapter flange that will slowly taper from the cat's 2.5" size to the 60mm size so the system will still flow smoothly.
 

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i have to say i was very pleased w/the greddy header & evo catback combined, but i have a custom cat to fit the piping evenly, so im not sure about what cat to use..
 

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Discussion Starter · #4 ·
Well, my goal of 200 whp probably won't happen for a long time. For the imediate future the only mods that I'll have will be I/H/C/E. If this is the case should I just stick with 2.25" or 60mm exhaust? If I do go with the 60mm exhaust, should I get the 2.5" cat with the step down adapter? Are there any headers that are 60mm or 2.25"? If so, which ones? Budget is a big concern for me, a full time student with a part time job. Thanks for the help.
 

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not sure of budget but heres what i paid.. it hep w/decision in regards to what size considering you know size of greddy...
header-$359
cat-back-$499
custom cat-$70
 

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The JDM ITR header you can say is a little smaller as it has a 2.25" ID collector, but it is still 2.5" OD and will need a 2.5" cat to go with it.

I'd do it right the first time, sucks redoing things let me tell you. I've changed my entire I/H/C/E setup with this car because I messed it up the first time and that's alot of wasted money.
 

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Discussion Starter · #7 ·
I want to go ahead and put in 2.5" all the way through, but will I just be hurting myself? The only mods that I'll have on my car for a long time will me I/H/C/E. There's no way that my GSR will be cranking out over 210 whp with just I/H/C/E. I might be able to bore mine out to 2.0 L though (I got the hookup with someone). SurferX, in your article you say that I shouldn't oversize my exhaust either. Would putting in 2.5" be too big? Thanks again.

PS: How much performance is gained by boring out the engine?
 

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to be honest... 2.5" is just right anything bigger is for forced induction...
Also, boring out will give you more torque & about 5 hp w/no mods.
 

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You won't hurt yourself with a 2.5" system. The big problem with oversizing are when people have a stock sized 2.0" header and cat mated to a 2.5-3.0" exhaust. If you size it correctly throughout the system it will work good.

The exhaust sizing chart is only a general guide. The most important thing is how the header-cat-exhaust are sized together. You can stick with a 60mm exhaust on the 2.5" header-cat setup and only sacrifice a couple HP in the high end if budget requires you to do that. Since the 60mm size is big enough for your horsepower output you won't be choking yourself off tremendously.
 

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Discussion Starter · #10 ·
Thanks, I think I will get 2.5" header and cat with a 60mm exhaust (budget). How much is the tapered 2.5" to 60mm connecter that you were talking about? SMSP is the one who sells the catalytic converters, right? You said that the DC JDM 4-1 headers were the cheapest 2.5" headers. Where could I buy these (I don't see them at modacar)? Are there any quality issues I should worry about with the DC JDM 4-1's? Thanks for all the help, you saved me from blowing a lot of money!
 

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Dave at SMSP does both the cats and flanges so he can set you up. He is a member on this site (SMSP) so email him with your planned setup and he'll know exactly what to get you.

Inlinefour.com I know at least sells the DC JDM.
 

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Discussion Starter · #12 ·
I also forgot to ask, since I'll be buying each component of the system seperately (when I get the money), would it be better to start at the exhaust and work my way to the headers, or start at the headers and work my way to the exhaust?
 
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