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Old 11-03-2001, 10:27 PM   #1
Scooby Specialist
Member#: 8635
Join Date: Jul 2001
Location: Texas
04 STI, 07 FXT

Default Cat removal on 1993 Impreza 1.8l

My daughter owns a 1993 impreza (base model). It has acquired an exhaust leak just before the cat. The stock exhaust looks crazy how it snakes the air before it heads straight back to the muffler. I was wondering about putting in a different Y pipe and removing the cat to help improve exhaust flow. Since the o2 is just before the cat, I would assume this should not cause any computer problems.

Any comments?


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Old 11-03-2001, 11:03 PM   #2
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Member#: 6585
Join Date: May 2001
Location: Wits End,PA
1997 acura integra
champion white


you shouldnt experence any computer problems, i have an L also, and the flow on the front pipe looks a little restrictive. my thoughts were maybe trying the front pipe section from a 2.2 or a 2.5 if they'll fit.
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Old 11-04-2001, 06:03 AM   #3
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Chapter/Region: MWSOC
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'01 GC8 Dinged STM
'09 Concours 14 ABS Black


oh yes....if you remove the cat and go to a free flwoing exhaust kiss ANY torque that car makes goodbye. IIRC the RS or OBS exhaust is a totally different make up.

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Old 11-04-2001, 12:58 PM   #4
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Location: Manchester, NH
MY04 Foz XS
MY02 Imp TS


I'd invest in a cat back exhaust, and if you're bent on replacing/removing the cat, I'd just get a slightly larger high flow cat... there's no sense in completely removing that cat on a small displacement N/A motor, you'd feel some pretty bad power losses, I'd think.
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Old 11-04-2001, 05:48 PM   #5
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Chapter/Region: MAIC
Location: Bel Air Md.
2005 Legacy GT wagon
2009 Forester X


Be carefull removing the cats,I just installed a high flow cat on my RS.Got the ole check engine light after about a 100miles.It doesnt worry me cause im sure its the O2 sensor readin weird.Yep did an ECU reset.Lost a little at the bottem end but picked it up on top.The engine just wants to go(godamn rev limiter).
Just thought id add that if your worried about CEL's.
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Old 11-06-2001, 07:10 PM   #6
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Location: Sin City
1993 Impreza GCStyle


How would removing the cat reduce torque??? If you say backpressure, I'll laugh. Anyone who has ever tested exhaust systems will prove that its the exhaust velocity, not backpressure that makes or breaks hp. As for the CEL, the backpressure can help the o2 sensor heat up to operating temp sooner.

I upgraded my 1.8L cat to a 2.25" cat designed for a turbo chrysler. The power gain was VERY nice, probably because the turbo went on at the same time.

93 1.8T
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