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Old 10-03-2010, 11:55 AM   #1
Dknits782
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Default exhaust?

Hey I'm looking at getting a cat back exhaust for now and waiting for them to release a bolt up header to get the rest my friend runs a 3in on his 2.5i and he can get me the same at a super good deal but my question is isn't a 3in to big for our car not enough backpressure I would run 2.5 from the header to te cat the 3 out
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Old 10-03-2010, 02:01 PM   #2
iRazor
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backpressure=bad for 1 and for 2 a n/a car shouldnt really go over 2.25' otherwise you lose all your low end torque 2.5' is just about pushing it
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Old 10-03-2010, 02:04 PM   #3
nairbmik
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Whoever told you that that thing about backpressure, go ahead and slap them in the face. The backpressure thing is a MYTH. Exhaust velocity is the term you're looking for, since backpressure in any application is BAD.

Anyway, 2.25" is the size that most NA owners go with.
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Old 10-03-2010, 02:13 PM   #4
Dknits782
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OK cool thanks should I tell my friend to get new cat back will 3in cause any damage besides power loss
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Old 10-03-2010, 02:22 PM   #5
sol_tegra
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no, it wont cause any harm other than low end power loss!!!!
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Old 10-03-2010, 02:48 PM   #6
Dknits782
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LOL I think power loss is a big deal but my friend is kinda ricer like LOL but I will tell him thanks for all the input
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Old 10-03-2010, 09:14 PM   #7
RaineMan
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2.25... no need to go any bigger.
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Old 10-03-2010, 09:19 PM   #8
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Quote:
Originally Posted by RaineMan View Post
2.25... no need to go any bigger.
+1


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Old 10-03-2010, 11:04 PM   #9
PhilSine
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Quote:
Originally Posted by sol_tegra View Post
no, it wont cause any harm other than low end power loss!!!!
An accurate re-statement of this is that the torque curve will be move up the power band a bit and you'll gain better mid-range power.

The torque doesn't disappear, it moves to a different part of town where its more useful for driving on a track vs pulling the car from a dead stop.
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Old 01-11-2011, 07:40 PM   #10
Speedy2.5
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I just did a custom 2.25 with cat delete into a magnaflow muffler, i couldn't ask for any better sound or performance . I wouldn't want to go any bigger than 2.25 though.
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Old 01-11-2011, 08:55 PM   #11
RedGauge
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I have 2.5", it backfires, I am also catless. But I also have a turbo and no electronic engine management There are quite a few possibilities as to way it backfires, but I know its attributed to the bump from 1 7/8th to 2.5"

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Old 01-11-2011, 08:57 PM   #12
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I should add it only backfires after heavy acceleration.
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Old 01-11-2011, 11:54 PM   #13
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I am about to buy uel headers off of a 2005 2.5i for my 98gt. I have a 2.5" cat back system now and just want to get rid of the old raspy sounding headers. Any suggestions? Has anyone here done this?
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Old 01-13-2011, 09:30 PM   #14
Speedy2.5
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correction, mine is 2.5. sounds amazing
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Old 01-15-2011, 06:51 PM   #15
Millhouse_5
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There are plenty of NAs on here that are running 3" exhaust. and lots of people love it. You will loose some low end power (about 3k and under, and from what I've read its noticeable but not dramatic) and gain some top end, but it really is a matter of personal preference. If you like the sound of a 3" or spend a lot of time at the top end go for it. If you're going for all performance, stick with 2.25 max

Last edited by Millhouse_5; 01-15-2011 at 07:03 PM.
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Old 01-15-2011, 06:56 PM   #16
mrcrawford84
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I enjoy my 3in catback.
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Old 01-15-2011, 11:17 PM   #17
GEE-OTTO
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Well there probably will NEVER be a bolt up header for the 2.5i so you will be waiting for a long time. 3" is over kill hell 2.5 is pushing it 2.25" inch is about right your motor doesn't flow enough air to merit that large an exhaust down low or up top. Unless you like loud,which you must, 3 in is just too big.
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Old 01-15-2011, 11:46 PM   #18
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Quote:
Originally Posted by Millhouse_5 View Post
There are plenty of NAs on here that are running 3" exhaust. and lots of people love it. You will loose some low end power (about 3k and under, and from what I've read its noticeable but not dramatic) and gain some top end, but it really is a matter of personal preference. If you like the sound of a 3" or spend a lot of time at the top end go for it. If you're going for all performance, stick with 2.25 max
Quote:
Originally Posted by mrcrawford84 View Post
I enjoy my 3in catback.

I have a 3" and while it is a bit loud sometimes I dont mind it at all. I would like someway to tone it down when Im driving through town at 11 or later and dont want to attract attention. Other than that I can only tell a difference when the AC is on, then it pulls like a dog.
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Old 01-17-2011, 12:11 PM   #19
xTWiTCHx_Bugeye
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if you could send me a message of where a good web site for an 02 subaru impreza rs, catback exhaust is i would appreciate it
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Old 01-17-2011, 05:09 PM   #20
DCfreak2010
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Quote:
Originally Posted by xTWiTCHx_Bugeye
if you could send me a message of where a good web site for an 02 subaru impreza rs, catback exhaust is i would appreciate it
You can get 3" or 2.25". Nvidia, greddy, hks, tanabe, Espelir. They all make nice exhaust. But if ya want a true rumble you have to get Uel headers otherwise I don't think you will be satisfied. I have an 06 2.5i with Borla uels Rallisport hi flo cat and greddy tic catback. Spent about $1400 on the whole system. But it's worth it it sounds better than an Sti haha. Well an Sti with just a cat back on it lol. It's loud but badass.
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