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Old 01-18-2011, 08:35 PM   #1
DiscoBerry
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Default 3inch Wrx cat back on 2006 2.5i

Hi, I just bought a 3inch wrx catback off a bugeye wrx wagon and Im wondering if it will need to be modified to fit my car which is a 2006 impreza 2.5i wagon. I dont think the stock exhaust is 3inch so will I need adapters or new flanges welded on the exhaust. I got a really good deal on it and i would like to make it fit but if its not possible it not a huge loss to me.
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Old 01-18-2011, 08:43 PM   #2
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An exhaust shop should be able to make it work.
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Old 01-18-2011, 09:18 PM   #3
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You'll loose power and low end torque from that large of piping on an NA car. However, you can keep the axleback portion and just install that. You won't loose power by changing the piping that far back. You won't get any gains just the axleback either. You really won't get anything from the catback, so yeah.

Don't install the midpipe... that's what will cause a loss in power.
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Old 01-18-2011, 09:42 PM   #4
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ok but am i gona have to modiffy the axle back down to the stock pipe size or will the flanges mate up?
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Old 01-18-2011, 10:02 PM   #5
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Quote:
Originally Posted by DiscoBerry View Post
ok but am i gona have to modiffy the axle back down to the stock pipe size or will the flanges mate up?
At a welding/muffler shop, they'll probably just make some correct size tubing from the muffler to the midpipe. The size doesn't matter at that point since it's so far back in the overall exhaust system. I had it done for my both of the Prodrive axlebacks I bought. They were for a WRX and I fitted them on NA subies.
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Old 01-18-2011, 11:02 PM   #6
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Quote:
Originally Posted by DiscoBerry View Post
ok but am i gona have to modiffy the axle back down to the stock pipe size or will the flanges mate up?
The exhaust shop will just cut the flange off and weld it straight to your stock pipe.
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Old 01-19-2011, 07:07 AM   #7
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I was under the impression that the WRX catbacks were compatible with the 2.5i as long as the body style was the same, or is that just for the newer models or is that just wrong all together
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Old 01-19-2011, 10:57 AM   #8
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Quote:
Originally Posted by Millhouse_5 View Post
I was under the impression that the WRX catbacks were compatible with the 2.5i as long as the body style was the same, or is that just for the newer models or is that just wrong all together
That is ALL wrong.
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Old 01-19-2011, 11:12 AM   #9
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Quote:
Originally Posted by cmiovino View Post
You'll loose [sic] power and low end torque from that large of piping on an NA car.
Opening up the exhaust is not going to cause a loss in power.

Last edited by Patrick Olsen; 01-19-2011 at 11:02 PM. Reason: Loss, not low
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Old 01-19-2011, 01:43 PM   #10
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Is there any adapter that can make my stock axleback flange mate up to the 3inch one. I would rather not have it welded on as i want to be able to just bolt the stock one back on if i need to.
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Old 01-19-2011, 02:32 PM   #11
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Again, take it to the exhaust shop and tell them what you want. They can do it.
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Old 01-20-2011, 02:21 AM   #12
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Quote:
Originally Posted by DiscoBerry View Post
Is there any adapter that can make my stock axleback flange mate up to the 3inch one. I would rather not have it welded on as i want to be able to just bolt the stock one back on if i need to.

Supers587 on RS25.com makes (or did make) an adapter that did just that..
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Old 01-20-2011, 01:49 PM   #13
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what is the size of the stock pipe at the axle back flange?
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Old 01-20-2011, 02:46 PM   #14
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Quote:
Originally Posted by DiscoBerry View Post
what is the size of the stock pipe at the axle back flange?
Measure it dude. It's your car, we're not going to spoon-feed you everything. If you wrap a string around the pipe, you can get a rough estimate of the circmuference of the pipe, and from the circumference, you can calculate the diameter.

Circumference divided by 3.14 = Diameter
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Old 01-20-2011, 10:51 PM   #15
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Quote:
Originally Posted by Patrick Olsen View Post
Opening up the exhaust is not going to cause a loss in power.
But you'll loose BACKPRESSURE!!!!!

Quote:
Originally Posted by DiscoBerry View Post
what is the size of the stock pipe at the axle back flange?
I'll give you a hint...it's between 1 and 2"
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Old 01-21-2011, 07:25 AM   #16
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Quote:
Originally Posted by DiscoBerry View Post
what is the size of the stock pipe at the axle back flange?
If you're going to do this yourself, you should be able to measure it yourself.

If you're going to let an exhaust shop do this, you don't really need to know this anyway.
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Old 01-23-2011, 09:40 AM   #17
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I had on my until this past weekend a GREDDY Ti-C 3" wrx exhaust, instead of using the centerpipe from greddy, I used an STI centerpipe, had it lengthened and flange rotated for the greddy axleback, cost me about $40 at a shop.

Since I am UEL and no cats, I have two resonators on my centerpipe and with the greddy, was once of the meanest sounding NA's you could here, but times are tight, just listed it for sale
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Old 01-23-2011, 10:26 AM   #18
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i put a stock 05 wrx cat-back from my old wagon on my forester. i had to add a 2" coupling, kart boy long hangers, and rotate the mid-pipe to cat flange about 45 degrees. but the flanges were the same size even though the diameter of the wrx CB is about 1/2" larger. slap the bitch on.
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Old 01-23-2011, 02:45 PM   #19
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I put it on yesterday, it fit fine but the whole system was about 4 inchs short to the cat flange so I Had to weld in a extention.
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Old 01-23-2011, 11:36 PM   #20
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Quote:
Originally Posted by Patrick Olsen View Post
Opening up the exhaust is not going to cause a loss in power.
In most driving conditions, it will. There will be some loss in the low end and mid range, and the high end gains won't really be significant either, unless he has some engine work done. The N/A engines don't breathe well enough up top to warrant 3" pipe.
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Old 01-24-2011, 12:33 AM   #21
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Quote:
Originally Posted by Tim25RS View Post
In most driving conditions, it will. There will be some loss in the low end and mid range, and the high end gains won't really be significant either, unless he has some engine work done. The N/A engines don't breathe well enough up top to warrant 3" pipe.
Dude, this is like the 2nd or 3rd time you've been completely and utterly wrong in the last couple of days. Keep it up and we'll name you the new VISubie!

There will be no change in engine output based on changing the axleback or midpipe to a large size. They simply don't matter. No gains, no losses, nothing different other than the sound.
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