C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Eliminate pre cats?

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Old Aug 6, 2007 | 12:28 AM
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Default Eliminate pre cats?

I'm looking at this Y-pipe for sale at exotic muscle. Should I get any HP improvement? I have a Carsound high flow cat and catbacks with stock shorty headers.


C1151 STAINLESS STEEL FRONT Y-PIPE
This High Performance. Y-Pipe is designed to fit Corvettes 86-91. Recommended for off-road use only.

$ 195.95 ** APPLICATION: C4 / L98 86-91
http://www.exoticmuscle.com/webpage....CATSEL=EXHAUST
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Old Aug 6, 2007 | 12:57 AM
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do it. most smog folks can't ID a pre-cat from a calico.

the precats only work at startup... after that, they become power robbing pigs.

I would consider a high-flow main cat, too.
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Old Aug 6, 2007 | 01:12 AM
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Originally Posted by bogus
do it. most smog folks can't ID a pre-cat from a calico.

the precats only work at startup... after that, they become power robbing pigs.

I would consider a high-flow main cat, too.
Got one, a Carsound cat. I heard I can gain about 10 HP. Anybody have any info on this?

Last edited by Kool88vette; Aug 6, 2007 at 01:35 AM.
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Old Aug 6, 2007 | 02:05 AM
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You probably won't notice the difference in SOTP, but it will lower your underhood temps, which is always a good thing.
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Old Aug 6, 2007 | 02:07 AM
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I have always felt that the L98 exhaust was it's biggest problem. The main cat will help.

So will losing the pre-cats. I think all in all, it will add about 20hp. You can now do some work to the intake and get another 10 or 15. It all adds up.
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Old Aug 6, 2007 | 02:09 AM
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Either purchae a front y-pipe without the precats or take it to a muffler shop and have them cut off. Your choice. The only difference you will most likely notice is sound.
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Old Aug 6, 2007 | 08:18 AM
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Originally Posted by RRT vette
Either purchae a front y-pipe without the precats or take it to a muffler shop and have them cut off. Your choice. The only difference you will most likely notice is sound.
The ad says nothing about pipe size. Stock is 2 1/4. If the new pipe is 2 1/2 like the rest of the exhaust system I should see some HP improvement. Right?
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Old Aug 6, 2007 | 08:20 AM
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Originally Posted by bogus
I have always felt that the L98 exhaust was it's biggest problem. The main cat will help.

So will losing the pre-cats. I think all in all, it will add about 20hp. You can now do some work to the intake and get another 10 or 15. It all adds up.
I worked on the intake it has a superram and a 52mm TB.
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Old Aug 6, 2007 | 10:34 AM
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Originally Posted by RRT vette
Either purchae a front y-pipe without the precats or take it to a muffler shop and have them cut off. Your choice. The only difference you will most likely notice is sound.
no exhaust shop in the state of California would be caught dead removing emissions control devices.

Replace with the new part... it's a DIY project.
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Old Aug 6, 2007 | 10:37 AM
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Do it. I deleted my precats and went with Carsound (Magnaflow) on the main cat. It will probably be louder on decel.
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Old Aug 6, 2007 | 10:47 AM
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the exhaust is to restrictive on our vettes, but I'm not sure I'd pay the price their asking.
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Old Aug 6, 2007 | 11:30 AM
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$200 is way to much for that IMO. I would cut them off and use expanded end pipes with clamps, in the cats place. Or cut them off and have a shop weld pipe in. Either of witch would save money. And be less work since you don't have to try and remove the bolts from the manifolds.
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Old Aug 6, 2007 | 11:55 AM
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I had my cats cut off and sleeved. Just not sure they will do that in Kalifornea. It was $50.
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Old Aug 6, 2007 | 12:07 PM
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uh, lemme try this again:

NO CALIFORNIA SHOP IN THEIR RIGHT MIND WOULD REMOVE AN EMISSIONS DEVICE.
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Old Aug 6, 2007 | 12:11 PM
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Mine are removed+sleeved, definitely sounds better.
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Old Aug 6, 2007 | 12:32 PM
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Originally Posted by bogus
uh, lemme try this again:

NO CALIFORNIA SHOP IN THEIR RIGHT MIND WOULD REMOVE AN EMISSIONS DEVICE.
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Old Aug 6, 2007 | 12:45 PM
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Originally Posted by bogus
uh, lemme try this again:

NO CALIFORNIA SHOP IN THEIR RIGHT MIND WOULD REMOVE AN EMISSIONS DEVICE.
GOT IT THE FIRST TIME!
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To Eliminate pre cats?

Old Aug 6, 2007 | 01:13 PM
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Originally Posted by BADDUCK
GOT IT THE FIRST TIME!
Those damn Kalifornia smog *****. I just called a mechanic friend and he said it a big fine here if you get caught with no pre cats.
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Old Aug 6, 2007 | 01:14 PM
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Originally Posted by Kool88vette
Those damn Kalifornia smog *****. I just called a mechanic friend and he said it a big fine here if you get caught with no pre cats.
What part of illegal don't we understand?

It is illegal... they are just useless bits of added weight.

Get the new pipe and DIY. Check Performance Peddler, too.
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Old Aug 6, 2007 | 02:15 PM
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Originally Posted by bogus
no exhaust shop in the state of California would be caught dead removing emissions control devices.

Replace with the new part... it's a DIY project.
Didn't notice the OP was in California. In that case, purchase the front y-pipe and install.
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