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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
 

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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.
 

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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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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¢
 

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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.

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.

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.

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.
 

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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.
 

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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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the reason peoples cats tend to go out on stock vehicles is because the stock tune and pulley is so fat.... they are so rich its a joke. being too rich can quickly kill a cat, as well as being really lean (but the pcm has a COT feature, so unless you disable it, you cant kill the cat by leaning it out). DONT, DONT gut a stock cat. unless you plan on running more boost than a 2.8", and going extensively into mods (FULL exhuast, high boost, etc etc) dont even waste your time with getting rid of the cat, get a ZZP downpipe with a highflow cat.

also, ssnipes is 100% right. the GMPP exhuast is NOT the most powermaking system, and it can actually become restrictive if the highly restrictive header and downpipe is replaced.... it was actually made a 2.25" so it would work for both the 2.0 and the 2.4. if you put a full 2.5" with those straight thru mufflers on a stock/mild 2.4, you would LOOSE torque, and GM didnt want that (and they also didnt wanna make four different exhausts).

for those of you in the hunt for serious power, take some time to look over jmc's flow numbers, they will be quite helpful to you all.
 

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Who's company in Quebec are you talking about ? And about the stock catback, do you know that it only flows 300 CFM (just see te following link), which is CLEARLY NOT ENOUGH for a 200+ HP car !!!

http://www.corsaperf.com/chevy_cobalt.htm



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.



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.



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.



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.
 

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well i have an 07SS/sc and i have the GMP exhaust the first day i put it on i had the 420 cat code drop on me. since then i have put the K&n CAI and the GMP stage two upgrade my car is actually slower now my cat went bad
on me and i only have 5000 miles on the car the dealer is putting a new one one but i manage a meineke and im going to weld up a custom down pipe to eliminate the cat has anyone done this yet and how much gain is noticed? it was weird i knew it was resticted cuz it didnt pull like it used too while boosting and the boost gage would go to 20 psi because the cat wasnt letting it out and the waste gate was dumping the boost. thus the reason for 20 psi
 

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Flow: while plugged you will definately lose performance... but normally you will have a ton of flow from your stock cat, most cats are high flow from the factory.... notice I said "high flow" not "zero restriction".

Sound: a lot of people associate louder sound as more power, a lot of people even think they feel more power when they open their exhaust, I am here to tell you to put it on the dyno and prove it.... I hate to hear people talk out of their asses.

Legality: "I don't have emissions where I live" is a crock of crap. Emissions laws apply in all 50 states and in all counties in all of those states.... There are many places that do not "enforce" the emissions laws by way of a test station that you have to visit from time to time, but the law still exists and you can get busted for tampering with and/or removing any and all federal emissions equipment (including EGR, cats, PCV), all you have to do is give the cop a probable cause (ie loud exhaust or neons or wings) and he can check it and fine you for non compliance. technically for your performance parts to be legal for use on a highway driven car, it needs a CARB EO number on it.

Tuning nightmare: the other problem that you can create is a tuning nightmare. if you remove or hollowout your cat, your rear O2 sensor now sees everything as is the cat were'nt there and will tell the ECU that the Catalyst is inefficient, it will also see lots of oxygen and assume a lean condition exists and dump fuel to richen up the mixture.

Warranty: unless you know a service manager at a GM dealer, I would be willing to bet that if you come in with a failed cat and you tampered with emissions devices, your warranty claim will turn into customer pay and it will be you and not general motors that pays that bill. (I am a ASE certified master tech at a GM dealer)

these are all just things to keep in mind when modifying your car
 
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