How much hp does a catalytic converter steal?
 

Just curious

A stock one? About 10-15. An aftermarket one? About 5. Not worth gutting, unless you're cheap.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

Car Craft did a test on this about 6 months back on a supercharged 305 making over 315HP at the wheels. With the cats on, it lost 2 peak HP but gained 8lb/ft of torque from 2000RPM to its torque peak.

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1985 Z28, Jasper Class 1 350, Edelbrock Performer intake, Dual snorkel air cleaner, K&N, Edelbrock headers, Catco 3" cat, Hooker 3" cat-back, Richmond 3.73's, built 700r4 w/Darrell Young 2400 stall TC, JET Stage 2 chip, Hypertech coil, Lakewood LCA's, Powertrax locker, SSM subframes, Centerline Auto Drag's

Sure, and they probably failed to tune the engine for optimized operation with a more open exhaust. It probably leaned out whereas if they had bumped up the fuel a little more horsepower would have been realized without the cat. A catalytic converter merely adds backpressure, and I can't see how it would increase flow velocity better than a straight pipe. It is the velocity of the exhaust gases that must be maximized for power production, while the backpressure should be kept to a minimum. From a performance standpoint, there is nothing positive to be said about a catalytic converter. I really hate to get into this again.... https://www.thirdgen.org/messgboard/biggrin.gif.

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1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, MSD coil, 180 t-stat, Bald Eagle tires,
Hypertech fan switch, Accel 23# injectors, Holley AFPR, ported plenum,
Ported Daytona Yellow stock base, Moroso valve covers, other stuff,
Ruger P95DC, hot wife, new oil filter, thick rubber floormats, no cats.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

well, if u gut the cat and don't put a pipe inside of it, then can't the open area creat turbulence?

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88' GTA 350 MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT

i guess i am cheep i gutted it, why pay 100 when you dont even have to pass emissions and you need to get ride of back pressure. i would beleve that it would cause tubulance but there it should be nothing compared to the resistance of a stock cat.

Yes it does create turbulance. A gutted cat acts the same as a muffler, it redirects flow but doesent have a clear path to travel thus reducing HP.

To anyone how wants to gut thier cat! Please for the sake of GM spend 5 bucks and get a piece of pipe to stick in there galvinized pole is cheap and can be bought at home depo.
but dont use it for a replacement pipe.
SSC https://www.thirdgen.org/messgboard/smile.gif