My No Cat Dyno Experience
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,681
Likes: 2
From: Seven Devils NC
My No Cat Dyno Experience
So a bit of background ... I have a 2002 LS6 that has BB shorties gutted cat stock xpipe with stock TI exhaust. The motor has LS6 ported heads from Texas speed and a cam that is very near a G5X2 profile. Last year the car put down 426.
In late feb / march she dropped cyl 7 due to what I think was a week injector and common cyl 7 problem. Lost compression and I decided to rebuild back to stock. Motor was pulled and we honed the cylinders installed new rings on stock pistons as well as polished crank with new bearings.
Motor went back in and I decided to put a used Xpipe back on that had the cats intact then after a few baseline pulls the motor made a best of 416.5 at 11.75 Air/Fuel .... We then decided to put the Xpipe with cats gutted on and car belted out a 429.83 with 12.55 air/fuel. Both runs were 91.16F and 19% RH ...
So yes we took a bit of fuel away but do think the cats made the biggest difference ... I was always under the impression that cat removal was pointless but in my experience it did make a difference.
(note i may put them back on just cuz its not quite as loud and smells so much better)
In late feb / march she dropped cyl 7 due to what I think was a week injector and common cyl 7 problem. Lost compression and I decided to rebuild back to stock. Motor was pulled and we honed the cylinders installed new rings on stock pistons as well as polished crank with new bearings.
Motor went back in and I decided to put a used Xpipe back on that had the cats intact then after a few baseline pulls the motor made a best of 416.5 at 11.75 Air/Fuel .... We then decided to put the Xpipe with cats gutted on and car belted out a 429.83 with 12.55 air/fuel. Both runs were 91.16F and 19% RH ...
So yes we took a bit of fuel away but do think the cats made the biggest difference ... I was always under the impression that cat removal was pointless but in my experience it did make a difference.
(note i may put them back on just cuz its not quite as loud and smells so much better)
Drifting
Joined: Jan 2008
Posts: 1,722
Likes: 138
From: Florida
St. Jude Donor '09
I agree, I believe the cats are more restrictive than most think. This was my experience with my previous C-5.
http://forums.corvetteforum.com/1574501042-post11.html
http://forums.corvetteforum.com/1574501042-post11.html
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
Sorry, no amount of tuning will get rid of the stench-close your garage door for 10 minutes sometime with a car with cats vs. one without. Bet you'll change your mind then (assuming your still alive from the no-cat experience).
Drifting
Joined: Feb 2010
Posts: 1,720
Likes: 38
From: Colorado
having lived most of my life in AL, where you can smokescreen the town to the point the weather channel erroneously predicts a storm in your area, its kind of common to run w/o cats here. its widely known that if you're doing intake/exhaust mods, the cat becomes noticeably restrictive.
the added smell may or may not be worth it to you, depending on what you're doing, and if you live in a smog-test area you're boned.
dougbfresh: why dont you sit in a garage for 10 minutes with your engine running and let us know how that goes for you on any car? cat or not cat, these things dont spit out unicorns and pixie dust..
the added smell may or may not be worth it to you, depending on what you're doing, and if you live in a smog-test area you're boned.
dougbfresh: why dont you sit in a garage for 10 minutes with your engine running and let us know how that goes for you on any car? cat or not cat, these things dont spit out unicorns and pixie dust..
Burning Brakes
Joined: Jun 2009
Posts: 780
Likes: 0
From: Aquadale Speed Shop NC
Instead of getting into an internet battle with you I will simply say, please reread what I posted as it clearly says, "will HELP" with the smell, not totally cure the problem.
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Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
having lived most of my life in AL, where you can smokescreen the town to the point the weather channel erroneously predicts a storm in your area, its kind of common to run w/o cats here. its widely known that if you're doing intake/exhaust mods, the cat becomes noticeably restrictive.
the added smell may or may not be worth it to you, depending on what you're doing, and if you live in a smog-test area you're boned.
dougbfresh: why dont you sit in a garage for 10 minutes with your engine running and let us know how that goes for you on any car? cat or not cat, these things dont spit out unicorns and pixie dust..
the added smell may or may not be worth it to you, depending on what you're doing, and if you live in a smog-test area you're boned.
dougbfresh: why dont you sit in a garage for 10 minutes with your engine running and let us know how that goes for you on any car? cat or not cat, these things dont spit out unicorns and pixie dust..
My last Vette, a 69' had no cats-you would not want to be in a closed space for more than 2 minutes with that car running. If you think your doing much by removing the cats, your NOT. I live in an area where every 2 years we get tested-it's not worth the hassle (or the extra 2hp gain) to "F" with the cats. Cat's are not perfect, but it's a PROVEN fact, they do help cut down on the junk shot out the tailpipes that we ALL breath.
Guess some of us can ignore the laws we don't like just cause' we want to.
Last edited by dougbfresh; Jun 2, 2011 at 10:01 AM.
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
I definetly beg to differ. My garage has a 72 C3 454 with open sidepipes and a 68 mustang and neither one ever stink up the garage. I can let either car idle in the garage and never smell anything other than hot car (and burning oil in the case of the mustang) so if a carb can be tuned to not smell then a fuel injected car can too. This of course not to mention my catless C5 has no smell either. Just a simple mail order tune from ECS took care of that. On the stock tune it stunk like raw fuel. After the tune nothing.
Burning Brakes
Joined: Jun 2009
Posts: 780
Likes: 0
From: Aquadale Speed Shop NC
Don’t bother trying to reason with somebody that already knows everything....
May I suggest a Chevrolet Volt for you? I believe they are electric, it hardly emits any emissions. You'll save the world single handedly!
May I suggest a Chevrolet Volt for you? I believe they are electric, it hardly emits any emissions. You'll save the world single handedly!
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,681
Likes: 2
From: Seven Devils NC
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
I may be a little biased though, I really like the smell of gasoline, oil, burning rubber and that distinct iron and salt smell of all the blood and sweat I left inside the engine bay burning off.
Instructor
Joined: Jun 2007
Posts: 176
Likes: 0
From: Groveland Ca
I have a 98 with H/C, LT headers, X-pipe and no cats. It has a B&B
exhaust and can idle all day in the garage. The tune and air fuel ratio
is the answer!!!! It has 10K on the clock with no problems and my
county is smog exempt in CA.
exhaust and can idle all day in the garage. The tune and air fuel ratio
is the answer!!!! It has 10K on the clock with no problems and my
county is smog exempt in CA.
Team Owner
Joined: Mar 1999
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From: At the beach in little Rhody
Premium Supporting Vendor
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From: Providing the most proven supercharger kits for your C5/6/7 609-752-0321
I definetly beg to differ. My garage has a 72 C3 454 with open sidepipes and a 68 mustang and neither one ever stink up the garage. I can let either car idle in the garage and never smell anything other than hot car (and burning oil in the case of the mustang) so if a carb can be tuned to not smell then a fuel injected car can too. This of course not to mention my catless C5 has no smell either. Just a simple mail order tune from ECS took care of that. On the stock tune it stunk like raw fuel. After the tune nothing.
Le Mans Master
Joined: Oct 2001
Posts: 5,145
Likes: 125
From: The Motor City
Where was the wideband? If it was after the cats (ie. in the tailpipe), that's the reason why you got different A/F readings. Cats really mess with widebands. They should always be placed before the cat when tuning to get accurate readings.
