2.5" or 3" exhaust? - Pontiac G8 Forum: G8 Forums - G8Board.com
Exhaust Tech Headers, Catbacks, Mufflers, lack of mufflers

 
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post #1 of 7 (permalink) Old 12-16-2016, 02:23 PM Thread Starter
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2.5" or 3" exhaust?

Hey guys.... Just wondering how much difference in power is it gonna make going with a full exhaust with headers on my Gxp with a 2300 if I put a 2.5" vs a 3" exhaust? I don't want the car to be real loud and if power is'nt a big difference I'd rather a 2.5". Thanks for input ahead of time.
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post #2 of 7 (permalink) Old 12-16-2016, 03:34 PM
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Originally Posted by Jfireboy1 View Post
Hey guys.... Just wondering how much difference in power is it gonna make going with a full exhaust with headers on my Gxp with a 2300 if I put a 2.5" vs a 3" exhaust? I don't want the car to be real loud and if power is'nt a big difference I'd rather a 2.5". Thanks for input ahead of time.
Difference in power will be negligible, the sound will be different though. I run 3" through dynomax vts and get compliments all the time...

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post #3 of 7 (permalink) Old 12-16-2016, 04:57 PM
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I heard somewhere that the bigger the exhaust, the more power you can make. Not sure if it's true or not. Has this ever been proven?
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post #4 of 7 (permalink) Old 12-16-2016, 06:13 PM
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Watch this link and make up your own mind. The guys at Engine Masters seem convinced the 3" is the way to go if you want the most power.


2009 G8 GXP #808 of 1829, #30 of 61 in this configuration: SRM, 6MT, Roof

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post #5 of 7 (permalink) Old 12-16-2016, 06:31 PM
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2.2CFM/HP is the number. Any more flow, there is no power gain.

Read David Vizard's unbiased technical article - if you dare.

BTW, I'm told it's 1.5CFM/HP on the intake side.

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post #6 of 7 (permalink) Old 01-14-2017, 02:33 PM Thread Starter
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Well decided to go with the borla catback and just installed it today. Waiting on my Kooks lt's and connectors so will just run the catback for now. Must say that video clips of exhaust set ups do not sound the same once you hear them in person. I was a bit skeptical at first because some members had the set up I was looking at which the video is real sensitive to the pops and crackles to where you never really get a clear sound of how they really sound. Must say I'm very happy and can't wait to hear how it sounds with lt's.😁
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post #7 of 7 (permalink) Old 01-14-2017, 03:00 PM
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I have Solo HFCs and a Borla catback and have liked the way it sounds from day one. I get lots of positive comments on the way it sounds too.

2009 G8 GXP #808 of 1829, #30 of 61 in this configuration: SRM, 6MT, Roof

Rotofab CAI, Solo HFC, Borla Catback, Livernois ECM tune, Holley Coil Covers, Heater Hose Relocation, rear Brembos.
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