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Old 12-03-2003, 07:55 AM   #1
JDMSubaru
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Default 3" cat back for WRX...good idea or bad idea?

Does anyone know if this is beneficial for a stock WRX with no other engine mods?

Will I lose significant power at some points, etc.?
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Old 12-03-2003, 08:14 AM   #2
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I just installed one last night ona stock WRX and it seems to hit slightly higher boost and hold for longer on top end power. Bottom end feels better too.

Turbos need to breathe
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Old 12-03-2003, 09:10 AM   #3
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do it and be happy
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Old 12-03-2003, 09:58 AM   #4
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As you might expect, the jury is still out on the exact gains to be had numbers-wise (between 5 and 10 hp quoted typically).

But in general, you should notice only gains. I can't recall reading one case where someone said a 'name-brand' catback of 3"-diameter tubing actually detracted from performance.

Do a search on 'backpressure' if you're concerned about that issue w/a 3"... I don't want to start the 5-billionth thread-jack on that topic!

If nothing else, getting rid of the stocker's sewing-machine sound is worth it!

-James
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Old 12-03-2003, 11:31 AM   #5
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wow lots of noob posts

good idea.

an intersting read is max boost by corkey bell (turbo god)
the best exasut for a turbo car is no exasut.. the less back pressure you have after a turbo the better

however
you won't realize the potential of the system without some form of engine management a 3" turbo back +cobb stage 2 reflash = big power increase +50 whp
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Old 12-03-2003, 12:41 PM   #6
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imho: catback (3"+) on a totally stock wrx causes major low end torque loss (atleast for butt dyno and throttle response). For better gains get the Catback put on with a downpipe.
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Old 12-03-2003, 12:50 PM   #7
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3" = Awesome idea

I had permagrin for days, and my car felt very much torquier, BTW.

There are some that theorize that the turbo creates the backpressure needed for torque (since up-pipe pressures approach what, 40psi?), and that post-turbo pipe should be as backpressure free as possible. I belong to those, by the way...

TimK
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Old 12-03-2003, 01:01 PM   #8
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its a good idea, but it is the absolute worst bang for buck mod, and some people say it has less butt dyno pull.
batsy
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Old 12-03-2003, 02:42 PM   #9
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If you're totally stock, I personally would get a Cobb reflash stage 1. For the price of good cat-back (probably even less) you can get your ECU reflashed to Stage 1. According to Cobb's site, you shouldn't need to reflash again until you swap the downpipe I think.
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Old 12-03-2003, 02:52 PM   #10
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Please read on www.turbomagazine.com a wrx exhaust shootout on catback exhausts from many major manufacturers.

From that you can see if it's worthwhile to get one or not.
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Old 12-03-2003, 03:45 PM   #11
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Quote:
Originally posted by teiva-boy
Please read on www.turbomagazine.com a wrx exhaust shootout on catback exhausts from many major manufacturers.

From that you can see if it's worthwhile to get one or not.
lol..

Ultimately you're still suffocating the turbo with the 2-catted downpipe.
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Old 12-03-2003, 03:52 PM   #12
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Quote:
Originally posted by teiva-boy
Please read on www.turbomagazine.com a wrx exhaust shootout on catback exhausts from many major manufacturers.
Here's the link:
http://www.turbomagazine.com/tech/0212tur_exhaust/

Generally 10-15 hp & tq gain.

Tom
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Old 12-03-2003, 05:25 PM   #13
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Quote:
catback (3"+) on a totally stock wrx causes major low end torque loss (atleast for butt dyno and throttle response). For better gains get the Catback put on with a downpipe
oookay ...

the reason back pressure is relational to power on NA car is due to cyl scavaging .. the turbo will provide MORE back pressure than an exaust ever could so there is no merrit to the theroy that smaller exasut will increas power on a turbo car

that said the wrx ecu is sensitive enough that it may freak out some .. this is why the reflash plays such a important role
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Old 12-03-2003, 06:42 PM   #14
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call me a noob, but here is my theory.

as far as back pressure, when the exhaust exits the cylinder head and goes into the manifold it is forced through a tiny ass uppipe(I forget the actual dimensions), then goes through the turbo. All of these things will cause a certain amount of backpressure.Why some people feel that they need more is beyond me. I have a helixdp/blitz nur spec. all 3 inch, and there was no loss in torque that I could feel. I drove around with just the dp, and the difference was amazing(as well as being ungodly loud).Car pulled like a demon! It seems to me that the less backpressure after the turbo, the faster the spool up.
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Old 12-03-2003, 08:19 PM   #15
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nevermind
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Old 12-03-2003, 08:30 PM   #16
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Quote:
Originally posted by Happy_Days
imho: catback (3"+) on a totally stock wrx causes major low end torque loss (atleast for butt dyno and throttle response). For better gains get the Catback put on with a downpipe.
This is what I was worried about.

Can anyone else agree with this or confirm it?
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Old 12-03-2003, 08:55 PM   #17
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Quote:
Originally posted by Happy_Days
imho: catback (3"+) on a totally stock wrx causes major low end torque loss (atleast for butt dyno and throttle response). For better gains get the Catback put on with a downpipe.
Can't say I agree, Didn't feel any loss from my Cobb catback.

Tom
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Old 12-03-2003, 09:08 PM   #18
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Quote:
call me a noob, but here is my theory.
uh your a noob, haha

im just playing...backpressure is undesputadly bad, but what you need to concern yourself is exhaust velocity.

http://www.vishnutuning.com/exhaust101.htm

go there, read it, at least 5 times.
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Old 12-03-2003, 09:09 PM   #19
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BULL. Major low end loss. Bah. Bunch of hooey. You put a 3 inch exhaust on your car, make a few runs and all of your fears will be relieved. How can you say you will have a low end loss when your turbo starts to spool a heluvalot sooner. More boost+sooner in the rpm range=BIG FUN!\
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Old 12-04-2003, 02:20 AM   #20
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Quote:
Originally posted by Rickyh
BULL. Major low end loss. Bah. Bunch of hooey. You put a 3 inch exhaust on your car, make a few runs and all of your fears will be relieved. How can you say you will have a low end loss when your turbo starts to spool a heluvalot sooner. More boost+sooner in the rpm range=BIG FUN!\
whatever you guys like.. i've tried wrx's stock with just a 3" catback replacement... lazy spool.
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Old 12-04-2003, 03:51 AM   #21
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Heres some info on the exhaust design. Read most of it, some really good info. Even has some stuff for NA cars further down. Cobb seems to know there stuff, i don't know if this was written by one of them, but they put it on there site so im sure it is valid. ANyways enjoy!


http://www.cobbtuning.com/tech/exhaustdesign/index.htm



PS
I believe this same question was asked a while back, so you can do a search for more info on the subject.l
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Old 12-04-2003, 05:23 PM   #22
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Quote:
Originally posted by JDMSubaru
This is what I was worried about.

Can anyone else agree with this or confirm it?
the less restrictive your exhaust is the better on a turbocharged car... it would be better to do a turboback instead of catback... but a cat back is an impovement and will not cause loss of torque.
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Old 12-04-2003, 05:26 PM   #23
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Quote:
Originally posted by Rickyh
call me a noob, but here is my theory.

as far as back pressure, when the exhaust exits the cylinder head and goes into the manifold it is forced through a tiny ass uppipe(I forget the actual dimensions), then goes through the turbo. All of these things will cause a certain amount of backpressure.Why some people feel that they need more is beyond me. I have a helixdp/blitz nur spec. all 3 inch, and there was no loss in torque that I could feel. I drove around with just the dp, and the difference was amazing(as well as being ungodly loud).Car pulled like a demon! It seems to me that the less backpressure after the turbo, the faster the spool up.
you may be a n00b, but your are correct... the less restrictive exhuast will improve your performance.
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Old 12-05-2003, 10:03 AM   #24
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Quote:
Originally posted by Happy_Days
whatever you guys like.. i've tried wrx's stock with just a 3" catback replacement... lazy spool.
Really? I had to adjust my boost map after I added my Cobb, as it was spooling sooner than I had mapped for in high gears. Had a 20+ psi boost spike.

Tom

Last edited by SlideWRX; 12-05-2003 at 10:09 AM.
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Old 12-05-2003, 11:13 AM   #25
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hosed, haha tom
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