Looking to hollow out my cat?!? - Chevy Cobalt SS Forum : Chevrolet Cobalt SS Forums
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post #1 of 14 (permalink) Old 06-19-2007, 12:28 AM Thread Starter
 
Join Date: May 2007
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Question Looking to hollow out my cat?!?

Im looking to hollow out my cat and i am looking for a o2 plug in that will trick the computer. do you guys know where to purchase one?
no emisions where i live.
matt
turbobuick is offline  
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post #2 of 14 (permalink) Old 06-20-2007, 06:11 PM
 
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^bad idea. The hollowed cat will leave a large hollow canister in your exhaust. That will trap hot air, and be detrimental to the flow of your exhaust. (And it will make an anoying 'buzzing' sound from the exhaust)

Just take out the whole DP, and have a shop weld together a custom DP without the cat, or buy one from ZZPerformance.

Then you will need somone with HP tuners to turn off your:
P0136, P0137, P0138, P0140, P0141, P0420, and other related cat codes.
socalsilverrl is offline  
post #3 of 14 (permalink) Old 06-22-2007, 07:54 AM
 
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One word - DON'T
codyss is offline  
 
post #4 of 14 (permalink) Old 06-22-2007, 09:09 AM
 
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hollowing out the cat is the redneck way of thinking you will get more horsepower, but you will not. The GMPP exhaust is actually smaller than stock yet gives you more tq/power, simply because the exhast flows faster and smoother than stock which ranges in size and the exhaust constantly speeds up and gets choked back down, if you hollowed out your cat then all you wuld do is speed it up then choke it back down. A cat doesnt really fuck with that much power unless your in the high stages a good flowing cat-back exhaust would be a better option. Just my .2
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post #5 of 14 (permalink) Old 06-22-2007, 12:56 PM
 
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my 2...

my STOCK cat went out at about 18K mi. That was without ANY tuning, or modifications to the engine. Just the GMPP Catback (which is one of the most HP producing exhausts...BTW).

Mine went out after 1 day of track time, with 95 mixed octane (91+100). Then it was made worse by a broken intercooler pump, causing higher exhaust temps.

Many people see their stock cat get clogged when going with smaller S/C pullies, and especially when leaning out the AFR's.

/my 2
socalsilverrl is offline  
post #6 of 14 (permalink) Old 06-22-2007, 04:49 PM
 
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Mine actually took a crap 3 weeks after Stage 2 was installed.

Still though holloing one out isn't the answer.
codyss is offline  
post #7 of 14 (permalink) Old 07-17-2007, 06:47 PM
 
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Quote:
Originally Posted by codyss View Post
One word - DON'T
WHY? The environment is a good reason. for a track car it is alright. not as an excuse but there are vehicles that leave more emmissions than we do being catless.

operationaly - there is ways around catless.

Quote:
Originally Posted by suprchged View Post
hollowing out the cat is the redneck way of thinking you will get more horsepower, but you will not. The GMPP exhaust is actually smaller than stock yet gives you more tq/power, simply because the exhast flows faster and smoother than stock which ranges in size and the exhaust constantly speeds up and gets choked back down, if you hollowed out your cat then all you wuld do is speed it up then choke it back down. A cat doesnt really fuck with that much power unless your in the high stages a good flowing cat-back exhaust would be a better option. Just my .2
It is not redneck, you will get more HP.

GMPP exhaust is small due to the expectations of having just GMS2 and also 2.25" is larger than other restrictions in the exhaust. the header is really small, the down pipe at the flex point is only 2"s so why go bigger GM thought. then aftermarket filled the void and made parts that work better. exhaust is the biggest way you can get HP and if you do complete exhuast, depending on modifications you have before making a change, can make 35HP difference.

speed it up and choke it back down....LOL ..... sounds like our cars have an illnees COPD Chronic Obstructive Pulmonary Disease....LOL but this would not happen. I have stock cat back with a ZZP header and 3" catless downpipe and it does not choke.

Quote:
Originally Posted by socalsilverrl View Post
my 2...

my STOCK cat went out at about 18K mi. That was without ANY tuning, or modifications to the engine. Just the GMPP Catback (which is one of the most HP producing exhausts...BTW).

Mine went out after 1 day of track time, with 95 mixed octane (91+100). Then it was made worse by a broken intercooler pump, causing higher exhaust temps.

Many people see their stock cat get clogged when going with smaller S/C pullies, and especially when leaning out the AFR's.

/my 2
one of the most hP producing exhausts? lol there only way were going to know that is an independent test on the same car on the same day on the same dyno. it blow me away when people think of it as easy as 15HP gain is so much better than a claim of 12HP. they can be exactly the same with 3HP difference and depending on the car too. all cars come from the factory with more or less HP then the benchmark.

Quote:
Originally Posted by codyss View Post
Mine actually took a crap 3 weeks after Stage 2 was installed.

Still though holloing one out isn't the answer.
answer for what? More HP? it most certainly is but even better. rather than sink 600 or better in a catback. get the header and downpipe with cat if you wish instead. you will have better sound, more flow than any catback will ever deliver. I know of a company in Quebec who did 60lbs injectors, cams, header and downpipe and did 13.05 in 1/4. they used the stock rear exhaust and muffler.

CATBACK is not the way to go for performance on a budget.
ssnipes is offline  
post #8 of 14 (permalink) Old 07-19-2007, 06:23 PM
 
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CodySS is talking about its pointless to hollow it out. You would never notice a gain or even see a gain on a dyno by hollowing out your cat. Personally i hate having them on my cars.

I would remecomend running (for more HP) either highflow cat or no cat at all.. You wont beable to tell the difference between the two.
KlugSRT-4v2 is offline  
post #9 of 14 (permalink) Old 07-21-2007, 07:41 PM
 
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Most converters are already high flow stock, there main restiction is bends or restricted inlets/outlets.
codyss is offline  
post #10 of 14 (permalink) Old 07-23-2007, 07:06 PM
 
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Quote:
Originally Posted by codyss View Post
Most converters are already high flow stock, there main restiction is bends or restricted inlets/outlets.
who told you that. have you looked inside your pipe. have you heard the difference between the catless and stock exhaust. I can tell you there is a difference. I could not pull a Hemi R/T before, just keep up. now I pull them.
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