Does Catback exhaust equal lost torque??
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 842
Likes: 4
From: Corpus Christi TX
St. Jude Donor '05
Does Catback exhaust equal lost torque??
Many moons ago... I had Mustangs... Great cars for the time of life I was in back then. Anyway, on one of them, I installed a 2.5" Flowmaster American Thunder Catback exhaust system (at a whopping $219). The sound was super nice, but I lost a noticeable amount of torque.. very noticeable. I think it was due to a loss of exhaust gas scavenging. Is this a problem for the Corvette systems? I want the sound... but I don't want the loss of precious torque.
Le Mans Master
Joined: Sep 2007
Posts: 7,604
Likes: 8
From: Belleville Il
I'd say NO to torque loss.My car was run on a dyno jet last weekend,,All I have on the car is Blackwing Intake and Corsa Touring exhaust.13 runs were done (3 runs on the first round then 5 more pairs)The car "learned" and adjusted air/fuel each pair, Wound up 346ft lb at the wheels.I'd say that I gained torque. 
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Burning Brakes
Joined: Dec 2006
Posts: 1,092
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From: Deerfield VA
St. Jude Donor '07
Thank you! You said first what i intended to, torque is never "lost" it just comes on harder higher up on the RPM scale. Not a big deal with a V-8 engine. what ails most 2 valve engines is their inability to breathe at upper
RPMS, headers, midpipe, and catback all rectify that problem to the the extent of the flow of the heads/cam.
BTW, my Mustang got "softer" out of the hole with headers, midpipe and catback, but MORE than makes up for it 3000 RPMs UP!
John
Race Director
Joined: Jan 2006
Posts: 10,554
Likes: 33
From: Not on either liberal coast.
Most exhaust systems do this...move your torque/horsepower up where most (street car) owners least want it.
Most owners want torque/horsepower down low and that's why gear changes might be more beneficial than exhaust in most cases.
Le Mans Master
Joined: Sep 2007
Posts: 7,604
Likes: 8
From: Belleville Il
Torque is not a problem on LS1 engines,I dug out the Full rpm logs from the Dyno runs. at 1750 RPM The first run had 164ft lb,,,on the last it had 204 ft lb @ 1800 with Corsa touring. At 2000 RPM #1- 247ft lb and the last one 287 ft lb Plenty of low RPM torque. On vets I'd call cat back torque shift a moot point,you'll never notice it.
Premium Supporting Vendor
Joined: Oct 2004
Posts: 36,838
Likes: 438
From: Manassas Park VA
St. Jude Donor '07-'08,-'13-'14, '16-'17
No, because most aftermarket Cat Back, or as the industry calls them, Axle Backs, are made with 2.5" pipe.
If you make an exhaust and go to 3" then you will have a loss do to a lack of scavenging, unless you have boost
Peace
Chip
If you make an exhaust and go to 3" then you will have a loss do to a lack of scavenging, unless you have boost
Peace
Chip
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Tech Contributor
Joined: Jan 2004
Posts: 20,030
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From: Wylie TX --> Less is More, except under the hood !
What you way makes sence, but I'm confused now. LG's dyno tested there new Big 3 (3" exhaust) against stock Z06 Ti's (2.5") and gained torque across the entire RPM range.
See here.
http://forums.corvetteforum.com/show....php?t=1960487
Toque
