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Old 07-10-2007, 01:39 AM   #1
Redboss
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Default Replace WRX exhaust with stock STi exhaust? pro's and con's?

Hi. I haven't done any exhaust mod yet and I plan to keep it pretty conservative. I may have an opportunity to buy an 07 STi exhaust system. Will this make sense on an 07 WRX? I'll get the catless downpipe and a stock look no? A few HP and quicker spool up? I've been searching for days and I'm learning a few things but couldn't find specific answers for this one. Thanks.
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Old 07-10-2007, 01:49 AM   #2
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From my understanding the STI exhaust does flow quite well. Not as good as a AM 3". But I hear people run stage 2 software with a AM downpipe and a STi Exaust.

That is what I plan to do.
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Old 07-10-2007, 02:03 AM   #3
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Well I was hoping I'd get the trifecta with the STi downpipe + in that I could pass visual, emissions and only spend a few hundred bucks. Am I dreaming? I've got the Vishnu reflash so hopefully this could hold me for a while so I can address some exterior improvements.
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Old 07-10-2007, 02:08 AM   #4
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you won't get much of a gain by going with the STi downpipe...

for the best gain... go catless.... but then again, living in cali is a crappy place to be a car enthusiast

if you're worried about the fuzz, maybe go with the sti piece...
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Old 07-10-2007, 02:29 AM   #5
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There's a lot more knuckleheads that will divert the police's attention, still I like the idea of being stealth. Isn't the STi downpipe catless? Another option I was exploring was the Helix catted downpipe. They claim it will pass CA emissions test. How do these compare?
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Old 07-10-2007, 06:39 AM   #6
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the sti downpipe does have cats in it.
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Old 07-10-2007, 12:41 PM   #7
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Well that's that then. I'd be completely lost w/o this forum. Thanks all.
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Old 07-10-2007, 12:53 PM   #8
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the exhausts are THE SAME



no gain going from a wrx exhaust to an sti exhaust...save your money
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Old 07-10-2007, 12:55 PM   #9
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But isn't one like super sti cool
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Old 07-10-2007, 01:01 PM   #10
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Only difference is the STi axleback sounds much better.
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Old 07-10-2007, 01:02 PM   #11
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sti axel back for the look and sound
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Old 07-10-2007, 01:06 PM   #12
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Quote:
Originally Posted by djsniggedy View Post
the exhausts are THE SAME



no gain going from a wrx exhaust to an sti exhaust...save your money
This is true. The downpipe is EXACTLY THE SAME. So is the uppipe. The resonator might be different (not sure), and the axleback is different. None of the STI exhause parts will free up any noticeable power. Don't waste your money.
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Old 07-10-2007, 01:13 PM   #13
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So I'm wrong again. Back to the drawing board. Perhaps a Helix catted DP. I hear they'll pass the sniffer out here. Or maybe the Stromung?
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Old 07-10-2007, 01:19 PM   #14
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I have an STI exhaust on my WRX. I like it. It has just the right amount of noise without being annoying and the ballsy rumble lets my wife know when I get home.

If you can get one cheap, like I did, it's well worth it.
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Old 07-10-2007, 01:38 PM   #15
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Why are you worrying about smog/emissions this early in the game? You car is brand new, you won't need to get smog checked before 2011 or so.
And even if you have to get smog checked, the smog station will need to put the car on 4-wheel dyno which they probably won't have. They'll end up doing a "static" check at 2500 RPM or so in neutral. I can't imagine failing emissions at 2500 RPM in neutral (virtually no load on the engine) with a catted downpipe (unless the car is badly tunned).
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Old 07-10-2007, 01:45 PM   #16
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I've had no problems with my perrin catted downpipe. Didn't run into any problems passing inspection with the single catted downpipe, so you should be fine with the helix catted downpipe or whichever you may choose. Hey look its a cat! ding ding ding you pass
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Old 07-10-2007, 02:06 PM   #17
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Thanks again. I thinks I'll just go with the downpipe. I'm not after sound but performance. I just don't want to be putting out an illegal amount of emissions. I remember buying an old Volvo for the wife and got it smogged at a funky little shop down the road. Later I had a mechanic tell me there was no cat in the exhaust system!
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Old 07-10-2007, 02:09 PM   #18
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Quote:
Originally Posted by Redboss View Post
Thanks again. I thinks I'll just go with the downpipe. I'm not after sound but performance. I just don't want to be putting out an illegal amount of emissions. I remember buying an old Volvo for the wife and got it smogged at a funky little shop down the road. Later I had a mechanic tell me there was no cat in the exhaust system!
some cars burn clean enough such that they will pass w/o a cat. I believe NA Subarus are within that bunch, but I am not sure. I do know that Dyno-Comp's '04 STi track car passed cali smog with a single hi-flow. You gotta remember...despite all the power, it's still just a four-banger.
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Old 07-10-2007, 02:15 PM   #19
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your 07 wrx is exempt from smog for 6 years from the model date.unless you are pulled over and sited for modified emissions,or selling it.

AWD is exempt from the enhanced dyno testing,but TSI testing is still required

a modified down pipe unless C.A.R.B approved, is illegal regardless if it passes tailpipe emissions or not so if the tech see's it, its a fail.

also unless the wrx is on a list of exempt from OBD2 testing or CAN,i dont think subaru has switched to CAN yet? i havent seen a sub that new in here yet,many computer reflashes,MAPs etc. can cause problems and fail.

im a smog tech in the north bay any questions feel free to pm me

cheers


adding: 1996 + needs a OBD2 certified cat,you can not add or subtract them either,its factory or fail essentially
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Old 07-10-2007, 02:20 PM   #20
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stock wrx catback has a 2.25" diameter piping. the stock STi catback has a 2.5" diameter piping. if you're running a stock downpipe and run a sti catback you wont feel a damn thing in difference
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Old 07-10-2007, 02:21 PM   #21
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Go steathback.
turbo XS
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Old 07-10-2007, 03:19 PM   #22
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Quote:
Originally Posted by Brock31 View Post
Only difference is the STi axleback sounds much better.
Maybe at Stage 0. But I switched out my Prodrive Oval last week for a STi muffler which is mated to a Cobb catted DP, STi midpipe, STi UP, and the STi muffler sounded so raspy and tin can like. Was not a fan really, but looked good and stealthy. Went back to the Prodrive and couldn't be happier.
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Old 07-10-2007, 03:22 PM   #23
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Pro's - none

Con's - Cost

The sounds is so minutely different that I would say its a bad use of money. I know a guy with an STI turbo back and I didnt know until he told me. Then I laughed at him...
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Old 07-10-2007, 03:30 PM   #24
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Quote:
Originally Posted by eurospek View Post
Maybe at Stage 0. But I switched out my Prodrive Oval last week for a STi muffler which is mated to a Cobb catted DP, STi midpipe, STi UP, and the STi muffler sounded so raspy and tin can like. Was not a fan really, but looked good and stealthy. Went back to the Prodrive and couldn't be happier.
I just put a STi axleback on my stock WRX exhaust 3 days ago and it sounds nothing like that. I've got a gutted stock UP, that is the only other mod. At idle and low rpm the tone is much deeper and I can only tell a minor dB increase at higher RPM's. I bought the whole TBE off a guy for $150, but have only put on the muffler at this point.
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Old 07-10-2007, 03:33 PM   #25
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Quote:
Originally Posted by Brock31 View Post
I just put a STi axleback on my stock WRX exhaust 3 days ago and it sounds nothing like that. I've got a gutted stock UP, that is the only other mod. At idle and low rpm the tone is much deeper and I can only tell a minor dB increase at higher RPM's. I bought the whole TBE off a guy for $150, but have only put on the muffler at this point.
It's nothing like that cause you still have two restrictive cats in there, unlike me.
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