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Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons Bolt-Ons | Intakes | Exhaust

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Old 08-19-2013, 06:06 PM   #1
Criag B
 
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How much HP 2.5 exhaust?

How much HP will 2.5 exhaust support in a N/A car?? Was wondering if it was worth it to go with a full 3in. system. Thanks.
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Old 08-19-2013, 07:24 PM   #2
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Originally Posted by Criag B View Post
How much HP will 2.5 exhaust support in a N/A car?? Was wondering if it was worth it to go with a full 3in. system. Thanks.
Zero. The factory exhaust is 2.5'', and flows pretty well. There is almost no gain to be had in 2.5'' exhaust. 3'' is overkill on an N/A motor unless you have some bigger cubes, high flowing heads and a beastly cam.
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Old 08-19-2013, 07:25 PM   #3
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Zero. The factory exhaust is 2.5'', and flows pretty well. There is almost no gain to be had in 2.5'' exhaust. 3'' is overkill on an N/A motor unless you have some bigger cubes, high flowing heads and a beastly cam.
IIRC the stock system is good to ~600RWHP. Then the 3" is not just for sound anymore.
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Old 08-19-2013, 07:27 PM   #4
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You won't get a true 3" system unless you buy one. I think KOOKS and LG are about the only ones that make a full header to exhaust tip in 3".

Most headers and cat-backs have a 2.5" connection point.

Unless you're making really big HP I wouldn't worry about going to a full 3" system. However, a 3" will give you a little bit of deeper tone when idling.
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Old 08-19-2013, 07:27 PM   #5
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IIRC the stock system is good to ~600RWHP. Then the 3" is not just for sound anymore.
I stand corrected OP! You're gonna need a whole LOT of cubes then lol.
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Old 08-19-2013, 07:31 PM   #6
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the magic number is 2.2cfm /HP. Any more flow is a waste of money.

Here is a decent unbiased article with science behind exhaust system design
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Old 08-19-2013, 07:33 PM   #7
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You won't get a true 3" system unless you buy one. I think KOOKS and LG are about the only ones that make a full header to exhaust tip in 3".

Most headers and cat-backs have a 2.5" connection point.

Unless you're making really big HP I wouldn't worry about going to a full 3" system. However, a 3" will give you a little bit of deeper tone when idling.
Lots of companies make a full 3".
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Old 08-19-2013, 08:07 PM   #8
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n/a i dont think the gains will be but like 1-2 hp if that. the weight of the extra pipe. will counter balance that tho lol
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Old 08-19-2013, 08:25 PM   #9
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Thanks for the replies. Looks like it's not worth changing to 3in.
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Old 08-19-2013, 08:34 PM   #10
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Sure it is. A 3" sounds like heaven on these cars.
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Old 08-19-2013, 08:52 PM   #11
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JRE has an 800 rwhp on the 2.5" exhaust. Blower car though


I run the Kooks 3". It does sound evil at the track!
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Old 08-19-2013, 09:19 PM   #12
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Quote:
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the magic number is 2.2cfm /HP. Any more flow is a waste of money.

Here is a decent unbiased article with science behind exhaust system design
Great read
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Old 08-20-2013, 10:07 AM   #13
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Lots of companies make a full 3".
Not a true 3". I'm talking about 3" from the collector back.

Most 3" cat-backs have a 2.5" inlet so they can connect up to the stock mid pipes. KOOKS makes a 3" inlet cat-back as well as LG. I think ARH might have one setup that way as well.
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Old 08-20-2013, 12:32 PM   #14
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Not a true 3". I'm talking about 3" from the collector back.

Most 3" cat-backs have a 2.5" inlet so they can connect up to the stock mid pipes. KOOKS makes a 3" inlet cat-back as well as LG. I think ARH might have one setup that way as well.
And so does JBA. And so does SW. I know what you're talking about. I just know there are plenty of full 3" choices .
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Old 08-20-2013, 03:13 PM   #15
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I have 1 7/8 kooks, 3×3 cats. Cut off the 2.5 " end of flowmaster AT welded on 3 inch end. 3 inches all the way back. Love it.
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Old 08-20-2013, 06:58 PM   #16
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I have 1 7/8 kooks, 3×3 cats. Cut off the 2.5 " end of flowmaster AT welded on 3 inch end. 3 inches all the way back. Love it.
That's what I'm gonna do one of these days. I bought the neck-down version of the JBA 3" long before I got the headers. Simple problem with a simple remedy!
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Old 08-20-2013, 08:04 PM   #17
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I slapped a Flowmaster 3" catback and center mount exhaust with the kooks and I live it!
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Old 10-29-2013, 08:47 PM   #18
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Needed to update this. Now making 741 RWHP and still using 1-7/8 kooks headers, kooks off road pipes and stock 2.5 pipes. Thinking it would help some to move to a full 3 inch exhaust?
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Old 10-29-2013, 08:55 PM   #19
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Needed to update this. Now making 741 RWHP and still using 1-7/8 kooks headers, kooks off road pipes and stock 2.5 pipes. Thinking it would help some to move to a full 3 inch exhaust?
Nothing drastic. $/hp you will be disappointed.
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Old 10-30-2013, 01:23 AM   #20
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ARH makes a full 3" kit
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Old 10-30-2013, 02:05 AM   #21
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Needed to update this. Now making 741 RWHP and still using 1-7/8 kooks headers, kooks off road pipes and stock 2.5 pipes. Thinking it would help some to move to a full 3 inch exhaust?
At 700+whp, a full 3in exhaust would have already been on my car.
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Old 10-30-2013, 07:17 AM   #22
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Waste of money for true dual 3" on these cars.
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Old 10-30-2013, 08:52 AM   #23
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Waste of money for true dual 3" on these cars.
Says the guy without a 3" exhaust.
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Old 10-30-2013, 03:09 PM   #24
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Waste of money for true dual 3" on these cars.
Funny u say that because a guy that dyno's 100's of Camaro's told me he never sees any gains from cars that switched to 3inch exhaust. He has told me when your over 800 +rwhp then it's worth it. Has anyone done any back to back testing switching the 2.5 to 3 on the dyno??
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Old 10-30-2013, 03:36 PM   #25
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Funny u say that because a guy that dyno's 100's of Camaro's told me he never sees any gains from cars that switched to 3inch exhaust. He has told me when your over 800 +rwhp then it's worth it. Has anyone done any back to back testing switching the 2.5 to 3 on the dyno??
Everything I have ever seen says you won't gain much of anything going to a 3". I choose to look at it differently. You don't really lose anything by going with a 3" exhaust either. I think the 3" catbacks sound a LOT better than any of the 2.5" I have heard.
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