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Old 08-22-2004, 02:25 PM   #1
BistroSti
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Default Gut the OEM STi DP

Has anyone gutted the OEM Sti DP? I was thinking about doing so since I now have my twin scroll on and a cat back. The only thing I was affraid of was a CEL.
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Old 08-22-2004, 02:50 PM   #2
carguyx
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there isnt any cat in the oem DP
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Old 08-22-2004, 04:14 PM   #3
Jitenshakun
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Quote:
Originally Posted by carguyx
there isnt any cat in the oem DP


There are 2 cats after your turbo. One in the dp proper and one in the mid-pipe.

If you gut the cat you'll get a CEL (low cat efficiency). You can get a CEL fix by wiring around it (Perrin has one) or going with a bung that has a small amount of cat material in it (godspeed does a nice one).

-J
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Old 08-22-2004, 04:18 PM   #4
T-WRX
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carguyx - I believe you are thinking of the stock STi uppipe.

BistroSTi - PM V6turboTA. The WRX and STi downpipes are the same. He put a gutted WRX pipe on his STi for a decent gain.

IMHO, you are much better off purchasing a bellmouth or divorced downpipe to free up the wastegate exhaust flow. You have a $30k car. Evidently you also have STi suspension parts (per your profile). Don't cheap out now.
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Old 08-22-2004, 08:48 PM   #5
BistroSti
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I have a 04 Sti and I have the JDM twin scroll turbo kit on it. The JDM DP is already a bell mouth, but is a bit diff than the none twin scroll bell mouth so after-market DP's are rare and expensive to import.
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Old 08-22-2004, 09:04 PM   #6
kedrin
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i used to use a gutted stock wrx down pipe. ran great.

do it its real easy if your a VERY good welder
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Old 08-22-2004, 09:19 PM   #7
BistroSti
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did you use the CEL fix?
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Old 08-22-2004, 09:37 PM   #8
kedrin
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yes i did. its also very easy and only cost me 2 dollars at autozone.
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Old 08-22-2004, 09:42 PM   #9
BistroSti
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did you just add a inline resistor?
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Old 08-22-2004, 10:02 PM   #10
kedrin
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i took two anti fouling adapters and drilled out on and screwed it into the other one then took the sensor and screwed it into the two adapters. Then took that and screwed it into the 3rd cat.
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Old 08-22-2004, 10:05 PM   #11
BistroSti
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eh,got a picture?
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Old 08-22-2004, 10:07 PM   #12
kedrin
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theres a DIY somehwer on here im sure. it has details and pictures. or try scoobymods.com
or
wrxfanatics.com (diy database.... we need one here)
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Old 08-22-2004, 10:14 PM   #13
BistroSti
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got a link can't seem to find it
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Old 08-22-2004, 10:22 PM   #14
kedrin
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Old 08-22-2004, 11:10 PM   #15
V6TurboTA
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If you want to check out what it could sound like check out the video I posted. Thats the gutted DP and 2nd cat (3rd cat off wrx) with my ghetto axle back. http://forums.nasioc.com/forums/showthread.php?t=604205

With just the cats hollowed it does pull nice, but it smells like hell. If I was to do it again I might just do the downpipe. I still have my stock 2nd cat so I can just throw it on to try it but im lazy.

I have the stock muffler on it now and I like it the way it is. Its pretty much like stock, but much deeper.

I did NOT cut my downpipe up to gut it. I just bashed the insides to pieces and pulled it out slowly but surely. Same with the 3rd cat.

I still have yet to run any impressive numbers with it tho...

~v6
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Old 08-22-2004, 11:14 PM   #16
kedrin
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Quote:
Originally Posted by V6TurboTA
If you want to check out what it could sound like check out the video I posted. Thats the gutted DP and 2nd cat (3rd cat off wrx) with my ghetto axle back. http://forums.nasioc.com/forums/showthread.php?t=604205

With just the cats hollowed it does pull nice, but it smells like hell. If I was to do it again I might just do the downpipe. I still have my stock 2nd cat so I can just throw it on to try it but im lazy.

I have the stock muffler on it now and I like it the way it is. Its pretty much like stock, but much deeper.

I did NOT cut my downpipe up to gut it. I just bashed the insides to pieces and pulled it out slowly but surely. Same with the 3rd cat.

I still have yet to run any impressive numbers with it tho...

~v6
hmmm im bored enough right now at 10 pm at night that im going into my garage to gut the extra 3rd cat i have sitting around lol. im gonna try your style.
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Old 08-22-2004, 11:15 PM   #17
Jaxx
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iirc the sti DP cat is bigger than the WRX DP cat... but the point is moot
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Old 08-22-2004, 11:18 PM   #18
V6TurboTA
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Quote:
Originally Posted by Jaxx
iirc the sti DP cat is bigger than the WRX DP cat... but the point is moot
Yes, I was told that also.
Not sure if its a better or worst thing once its hollowed out.

~v6
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Old 08-22-2004, 11:20 PM   #19
V6TurboTA
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Quote:
Originally Posted by kedrin
hmmm im bored enough right now at 10 pm at night that im going into my garage to gut the extra 3rd cat i have sitting around lol. im gonna try your style.
Try not to breathe too much of that crap in... its pretty deadly.

You will probably need a prybar and a hammer, or a BIG screwdriver or something like it.

Also you will get a CEL with it hollow unless you do the anti fouler CEL fix. (My CEL hasnt come back on in about 500 miles since the CEL fix, but I am told it still will occasionally pop up from time to time.)
That fix is simple, cheap, and fits on the STi like a glove

~v6
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Old 08-22-2004, 11:45 PM   #20
BistroSti
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nice clip, i'll post a vid up as soon as I have mine all done. I can't wait to hear it as the twin scroll header will delete the boxer sound.
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