Let's clear-up that 3" vs 2,5" Catback thing for the LSJ.
11-02-2011, 01:47 PM
#77
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GMPP catback is 2.25" (which I know you already know). So, I can see why he gained some horsepower.
I've found that a good 2.5" catback provides the best of both worlds (excellent exhaust gas velocity & flow).
Although, WSfraiser puts down around 350whp with a TVS & GMPP catback so, it's still debatable which setup is best.
I've found that a good 2.5" catback provides the best of both worlds (excellent exhaust gas velocity & flow).
Although, WSfraiser puts down around 350whp with a TVS & GMPP catback so, it's still debatable which setup is best.
11-02-2011, 01:55 PM
#78
I'm not saying a 2.5" catback is best for every setup, but it flows more than well enough for prob 90% of the SS/SC owners on here. It also provides excellent exhaust gas velocity which is just as important as flow.
The larger the pipe the slower the velocity, unless you are flowing the amount of air to compensate for the reduction in velocity (this I'm sure you already know).
11-02-2011, 04:44 PM
#79
Exactly. Cat-backs do NOT gain power on these cars, not enough to justify much cost anyway. I could port a stock manifold and gain more power than you will gain from swapping to a larger cat-back.
A good header, a well-made catless downpipe, and some free-flowing mufflers (which is part of the reason I like GMPP, the borla mufflers are very well designed and flow nicely for the size of the system, along with sounding great) is all you need. A 3" exhaust isn't needed on these or really any other car under 400hp. On a turbo car there can be gains due to better pressure differential across the turbine, but that doesn't apply on the LSJ cars.
A good header, a well-made catless downpipe, and some free-flowing mufflers (which is part of the reason I like GMPP, the borla mufflers are very well designed and flow nicely for the size of the system, along with sounding great) is all you need. A 3" exhaust isn't needed on these or really any other car under 400hp. On a turbo car there can be gains due to better pressure differential across the turbine, but that doesn't apply on the LSJ cars.
11-02-2011, 04:56 PM
#80
Exactly. Cat-backs do NOT gain power on these cars, not enough to justify much cost anyway. I could port a stock manifold and gain more power than you will gain from swapping to a larger cat-back.
A good header, a well-made catless downpipe, and some free-flowing mufflers (which is part of the reason I like GMPP, the borla mufflers are very well designed and flow nicely for the size of the system, along with sounding great) is all you need. A 3" exhaust isn't needed on these or really any other car under 400hp. On a turbo car there can be gains due to better pressure differential across the turbine, but that doesn't apply on the LSJ cars.
A good header, a well-made catless downpipe, and some free-flowing mufflers (which is part of the reason I like GMPP, the borla mufflers are very well designed and flow nicely for the size of the system, along with sounding great) is all you need. A 3" exhaust isn't needed on these or really any other car under 400hp. On a turbo car there can be gains due to better pressure differential across the turbine, but that doesn't apply on the LSJ cars.
as for me i got injen, badmab header, and corsa touring cat back ,stock dp. i know the dp is very restrictive, but listen to this! not my vid but same setup... sounds sooo sexy
Cobalt SS/SC Corsa Exhaust Pull Away - YouTube
11-02-2011, 09:53 PM
#81
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I believe he dyno'd 15whp from switching from a noodle header, 2.5" downpipe, and 2.5" catback to a badmab header, 3" downpipe, 3" catback. No doubt in my mind most of the restriction was found in the header.
I'm not saying a 2.5" catback is best for every setup, but it flows more than well enough for prob 90% of the SS/SC owners on here. It also provides excellent exhaust gas velocity which is just as important as flow.
The larger the pipe the slower the velocity, unless you are flowing the amount of air to compensate for the reduction in velocity (this I'm sure you already know).
I'm not saying a 2.5" catback is best for every setup, but it flows more than well enough for prob 90% of the SS/SC owners on here. It also provides excellent exhaust gas velocity which is just as important as flow.
The larger the pipe the slower the velocity, unless you are flowing the amount of air to compensate for the reduction in velocity (this I'm sure you already know).
https://www.cobaltss.net/forums/2-0l...-tuned-263910/
11-03-2011, 07:11 AM
#82
Well at least this guy picked-up 42whp from stock exhaust to open exhaust (cut-out):
https://www.cobaltss.net/forums/2-0l...-tuned-263910/
https://www.cobaltss.net/forums/2-0l...-tuned-263910/
From the words of Hennessey, and his HPE700 LS9 Camaro.... "The neat thing about superchargers is they are not real sensitive to exhaust back pressure. They just force the air out (so don't go shoving a banana in your tailpipe, because it will send it to the moon)".
Agreed, the only major increase u can get is catless dp and header.
as for me i got injen, badmab header, and corsa touring cat back ,stock dp. i know the dp is very restrictive, but listen to this! not my vid but same setup... sounds sooo sexy
Cobalt SS/SC Corsa Exhaust Pull Away - YouTube
as for me i got injen, badmab header, and corsa touring cat back ,stock dp. i know the dp is very restrictive, but listen to this! not my vid but same setup... sounds sooo sexy
Cobalt SS/SC Corsa Exhaust Pull Away - YouTube
Although, my stock downpipe has been slightly modified to remove the restrictive O2 sensor area.
Last edited by Staged07SS; 11-03-2011 at 07:12 AM. Reason: Automerged Doublepost
11-03-2011, 07:42 AM
#84
Senior Member
corsa sounds great , that car sounds almost like mine but ive got a modified GMPP setup, proper zzp shorty header and a catless custom dp which gets me compliments all day long granted every other catless LSJ ive heard sounds like poop. 
11-03-2011, 09:27 AM
#87
The old car smell....
My exhaust smelled just like my fathers 65 GTO's exhaust. While that's fine for a classic car, I got sick of smelling it on a daily basis with my car.
Although, I do miss the sweet smell race gas gives when I filled up with CAM2. Can't really smell anything with a cat re-installed.
My exhaust smelled just like my fathers 65 GTO's exhaust. While that's fine for a classic car, I got sick of smelling it on a daily basis with my car.
Although, I do miss the sweet smell race gas gives when I filled up with CAM2. Can't really smell anything with a cat re-installed.
11-09-2011, 01:59 PM
#95
People need to understand that bigger is not always better. You need to find the happy medium of exhaust flow & exhaust gas velocity.
What is your current setup??
11-09-2011, 02:41 PM
#99
You will def notice some more power after a tune. I would leave your exhaust as is, and focus on a tune. Your catless 2.5" downpipe should be flowing more than enough for your current setup.
11-09-2011, 06:51 PM
#100
Just curious...
Cause im currently on the fence on what to get.
But guys are making gains with a 3" over a 2.25 on a n/a cav eco.
Now im supercharged and plan on eventually going with the tvs...basically shooting for 300whp. Can I get away with a 2.5 and retain a somewhat good sounding exhaust or is the 3" going to make the difference?
The plan is a Bad-mab header, zzp catless 2.5" downpipe, cat, longest resonator I can fit, superturbo muffler.
Cause im currently on the fence on what to get.
But guys are making gains with a 3" over a 2.25 on a n/a cav eco.
Now im supercharged and plan on eventually going with the tvs...basically shooting for 300whp. Can I get away with a 2.5 and retain a somewhat good sounding exhaust or is the 3" going to make the difference?
The plan is a Bad-mab header, zzp catless 2.5" downpipe, cat, longest resonator I can fit, superturbo muffler.