No cats?
Thread Starter
Racer
Joined: Sep 2008
Posts: 375
Likes: 0
From: Dallas Texas
No cats?
I've had my headers on for about 3 weeks now and yesterday my engine started throwing a code. It's not sputtering or acting weird. I'm pretty sure it's an O2 sensor. I have a 3 inch x pipe with high flow cats. I want to cut the cats off and just have the O2 sensors tuned out.
Can anyone give me some pros and cons to this??
Thanks a lot.
Can anyone give me some pros and cons to this??
Thanks a lot.
Melting Slicks
Joined: Feb 2007
Posts: 3,266
Likes: 8
From: Indian Rocks Beach FL
St. Jude Donor '08-'09-'10
If you remove the cats you will get a fuel smell that can be hard to tolerate. You won't get any performance gain from running without cats. You can't tune out the front O2's, they are needed for the fuel system to operate correctly. You can tune out the rear O2's, which many people do with no ill effect.
You best solution lies in the tune, not butchering your exhaust system. Of course that's just my opinion.
You best solution lies in the tune, not butchering your exhaust system. Of course that's just my opinion.
Instructor
Joined: Oct 2005
Posts: 132
Likes: 0
From: Killeen TX
no cats
If you remove the cats you will get a fuel smell that can be hard to tolerate. You won't get any performance gain from running without cats. You can't tune out the front O2's, they are needed for the fuel system to operate correctly. You can tune out the rear O2's, which many people do with no ill effect.
You best solution lies in the tune, not butchering your exhaust system. Of course that's just my opinion.
You best solution lies in the tune, not butchering your exhaust system. Of course that's just my opinion.
Melting Slicks
Joined: Feb 2007
Posts: 3,266
Likes: 8
From: Indian Rocks Beach FL
St. Jude Donor '08-'09-'10
What you are talking about are O2 simulators, referred to as SIM's. They have been illegal for some time now and you can accomplish the same thing in your tune. The car should have been tuned when the headers were installed both to maximize their benefit and to ensure the car was running as it should.
Instructor
Joined: Oct 2005
Posts: 132
Likes: 0
From: Killeen TX
What you are talking about are O2 simulators, referred to as SIM's. They have been illegal for some time now and you can accomplish the same thing in your tune. The car should have been tuned when the headers were installed both to maximize their benefit and to ensure the car was running as it should.
Thread Starter
Racer
Joined: Sep 2008
Posts: 375
Likes: 0
From: Dallas Texas
If you remove the cats you will get a fuel smell that can be hard to tolerate. You won't get any performance gain from running without cats. You can't tune out the front O2's, they are needed for the fuel system to operate correctly. You can tune out the rear O2's, which many people do with no ill effect.
You best solution lies in the tune, not butchering your exhaust system. Of course that's just my opinion.
You best solution lies in the tune, not butchering your exhaust system. Of course that's just my opinion.
Drifting
Joined: Mar 2010
Posts: 1,628
Likes: 15
From: Seattle WA
You have high flow cats. They are not restrictive. You might gain 1-2 horsepower from removing them, and I think that's a liberal estimate. It would be easier to just lose some weight (either you, or the car) to get that advantage.
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Le Mans Master
Joined: Dec 2008
Posts: 5,414
Likes: 25
From: Texas
get the rear o2 sensors tuned out... your probably throwing po420/po430 codes for cat efficiency below threshold... the aftermarket high flow cats do not satisfy the computer like the OE ones....
you would have more of a fuel smell with no cats, and would prob only pick up a couple of HP running no cats, as stated above....
or find some rear o2 simulators to replace the rear oxygen sensors and to get rid of the codes...
you would have more of a fuel smell with no cats, and would prob only pick up a couple of HP running no cats, as stated above....
or find some rear o2 simulators to replace the rear oxygen sensors and to get rid of the codes...
Melting Slicks
Joined: Feb 2007
Posts: 3,266
Likes: 8
From: Indian Rocks Beach FL
St. Jude Donor '08-'09-'10
Drifting
Joined: Jan 2008
Posts: 1,722
Likes: 138
From: Florida
St. Jude Donor '09
The CATS, (at least the H-pipe with the pup-cats) are more restrictive than you might think. I have two H-pipes, a stock unit with the all four cats intact, and a modified version with not cats for auto-cross and track days.
With the stock exhaust manifolds and no other modification than the off-road h-pipe and a dyno tune, my completely stock MM6 LS1 produced 338 RWHP & 349 RWTQ.
I'm sure the tune had much to do with the power this car makes since the car was tuned by a reputable supporting vendor but I do not think it was responsible for all of the nearly 30 RWHP above what you normaly see on a 6-SP LS1.
With the stock exhaust manifolds and no other modification than the off-road h-pipe and a dyno tune, my completely stock MM6 LS1 produced 338 RWHP & 349 RWTQ.
I'm sure the tune had much to do with the power this car makes since the car was tuned by a reputable supporting vendor but I do not think it was responsible for all of the nearly 30 RWHP above what you normaly see on a 6-SP LS1.
Thread Starter
Racer
Joined: Sep 2008
Posts: 375
Likes: 0
From: Dallas Texas
Melting Slicks
Joined: Feb 2007
Posts: 3,266
Likes: 8
From: Indian Rocks Beach FL
St. Jude Donor '08-'09-'10
Team Owner
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From: S.W. Ohio. . . . . . NRA Life Member
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
maybe stock cats & pups but not High flow cats.
Safety Car
Joined: Jul 2001
Posts: 4,661
Likes: 67
From: Ocean Springs MS
The CATS, (at least the H-pipe with the pup-cats) are more restrictive than you might think. I have two H-pipes, a stock unit with the all four cats intact, and a modified version with not cats for auto-cross and track days.
With the stock exhaust manifolds and no other modification than the off-road h-pipe and a dyno tune, my completely stock MM6 LS1 produced 338 RWHP & 349 RWTQ.
I'm sure the tune had much to do with the power this car makes since the car was tuned by a reputable supporting vendor but I do not think it was responsible for all of the nearly 30 RWHP above what you normaly see on a 6-SP LS1.
With the stock exhaust manifolds and no other modification than the off-road h-pipe and a dyno tune, my completely stock MM6 LS1 produced 338 RWHP & 349 RWTQ.
I'm sure the tune had much to do with the power this car makes since the car was tuned by a reputable supporting vendor but I do not think it was responsible for all of the nearly 30 RWHP above what you normaly see on a 6-SP LS1.
Drifting
Joined: Jan 2008
Posts: 1,722
Likes: 138
From: Florida
St. Jude Donor '09
Adding any component to the exhaust system wheter it's a muffler, resonator or high flow cat will increase exhaust back pressure.
