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I want to put an exhaust cut out in my exhaust on my rex. I was going to get something from summit racing, basic manual cap-it-off style. But what size is the stock pipe before the muffler? I'm assuming this would be the place to have it welded in correct? Anyone else have any experience with this? Will it give me any performance gains? It shouldnt be TOO loud with all the other stock cats still in right? Im running a stock setup right now. Thanks for any help!
 

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i think the stock pipe is 2.75" but i'm not positive on that one...as far as the car not being to loud with the stock cats...when i was putting my turbo back on i turned the car on with just the factory down pipe on...the rest was off. It was really freaking loud...performance gains wise if you're putting it right before the muffler i wouldn't see anything much higher than 2-3whp...cause all you're really cutting out is the last muffler.

edit: ps: cut outs usually go closer to the motor, but i'm not sure on where the best placement and fitment would be on a rex
 

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i felt a noticable difference when i unbolted my rear stock muffler, but then again, i'm not really stock. i noticed a very large gain fromwhen i drove the car.it felt a little faster than when i normally drive by myself, but the difference was that there were 2 extra people in the car. my mods are headers, up pipe, intake, catless stealthback, and fmic. i only did that to see what kind of set up i needed for the cutout.seeing that it was way too loud, i'm going to get resonator put in before the cutout.i've been looking for an electric one.

peter
 

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The WRX is not 2.75"...

Here are the actual sizes:

Uppipe
- Inlet exhaust size is 1 1/2"
- Outlet exhaust size is 1 5/8"

Downpipe/midpipe
- Inlet/outlet exhaust size is 2 1/4"

Catback (rear exhaust pipe/Axle back)
- rear exhaust pipe inlet/outlet exhaust size is 2 1/4"
- Axle back inlet exhaust size is 2"

As for HP gain the ideal place would be before any cat-converters, but if you've got a stock turboback them I would recommend between the downpipe and midpipe. That way you've only got one obstruction (downpipe cat). you won't gain much if you install it before the muffler.

I dyno'd my car with the stock turboback -vs- NO turboback at all (open exhaust, no muffler, no, cats, no pipe, no nothing) and here are the results:



So your cut out should be 2.25" and should be as close to the front of the exhaust as possible.
 

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What boost were you running?
I've got stock boost (13.5:confused: I don't have a boost gauge), that dyno strictly show just the difference between exhausts, nothing else has changed.
 

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I have a 2.5" old school cutout I ordered from Jegs. It's installed before the muffler (for easy access in case I want to cap it off), just like you're wondering about.
Performance-wise, all I have is the cutout and an Accel Kool Blue high-flow panel filter. With these two mods, my WRX pulls noticeably stronger and it registered well on the ol' butt dyno. The turbo spools a bit quicker and like I said, it pulls harder for sure. The sound is absolutely great! I was expecting it to be louder, but it is relatively tame in my opinion. It has a nice lopey sounding idle and it can get respectably loud when you really get on it, but for the most part you'll have no reason to ever want to cap it off. Unless, of course, you're like me and would like to be able to cap it off to take it to the dealer for warranty work and have the car sound stock. Could they find it if they really wanted to? Of course they could! But, if they pull it in and it sounds stock, then why would they have any reason to start poking around?
Anyway, I think it's a great cost-effective mod that keeps the car looking stock (and sounding that way too, should you cap it off), but it sounds great and gives a respectable performance gain. I would tend to agree that the usual cutout placement is as far upstream as possible, but I wanted to have easy access to it and not choke on exhaust fumes if I'm stuck in traffic. So far, I've noticed no ill effects with the pre-muffler placement of the cutout.
I say do it...after getting it welded up, I was only out less than $55 for the whole setup. Plus, you can go back to stock at any time if need be with only 3 wing nuts.
I may be getting rid of mine for a custom system, but only in the name of saving weight off my wagon. That's really the only downside I can see to the cutout - the weight of still having the factory exhaust. Other than that, I think it's a great mod.

Good luck and let us know how it goes!:)
 
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