Cutting out cats

local392-496 · June 15, 2006

I got a 2003 Silverado w/8.1, i was wandering if i could cut the cats out and put straight pipe in their place. Does anyone know of any negative effects of this?

snoman · June 15, 2006

I got a 2003 Silverado w/8.1, i was wandering if i could cut the cats out and put straight pipe in their place. Does anyone know of any negative effects of this?

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Why is everyone so fixated with cutting out CATS's? There is no magic power to be found here and you can loose a little bit of low RPM torque and responce here too. Those dual cats flow well and effort would be better spent elsewhere. If you have the coin and really want to boost power, instal a intercooled supercharger and if you do it will respond well to it and it will get down right scary at times. Lso using 89 octane or better will improve it performance as well.

Freyguy · June 15, 2006

Yup, and I heard that if you do, it will throw engine codes because of the O2 sensors. There's some kind of O2 sensor delete plugs out there, but I think they are hard to find.

Superman TNT · June 15, 2006

Not sure what state you're in but in Vermont you will fail inspection for emmisions. If the cops catch you it is also a ticket. Not really sure what your reasoning was for cutting them out, power or increased noise but in either case there are better ways to do that. My 2 cents.

snoman · June 15, 2006

Yup, and I heard that if you do, it will throw engine codes because of the O2 sensors. There's some kind of O2 sensor delete plugs out there, but I think they are hard to find.

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The reason that the O2 can throw codes is because the gas expands and cools to much before it hits sensor with too little restriction and it does not heat sensors up properly to function correctly. On the eliminators, they are a poor fix because they are fixed value and provide no mixture feed back to engine so mixutre is rarely correct anf MPG as well as performance can suffer (especailly MPG)

Frozen001 · June 15, 2006

I may be wrong, but I believe that O2 sensors work through an chemical reaction the produces a voltage between two electrodes, and has nothing to do with EGT or pressure. The reason for the code is because most late model vehicles will have 2 O2 sensors one before and one after the CAT. this will verify the the CAT is working properly.

snoman · June 15, 2006

I may be wrong, but I believe that O2 sensors work through an chemical reaction the produces a voltage between two electrodes, and has nothing to do with EGT or pressure. The reason for the code is because most late model vehicles will have 2 O2 sensors one before and one after the CAT. this will verify the the CAT is working properly.

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You are right and wrong. They do work by chemical reaction with exhaust gasses but they do need to be at least a certain temp before that can provide vaild data so exhaust temp os very important to their proper function and one reason why they can go nutz on cut out systems. (as a foot note, the ECM ignores O2 sensor data during warmup because it is waiting for engine and O2 sensor(s) to heat up.)

Steady Eddie · June 16, 2006

" (as a foot note, the ECM ignores O2 sensor data during warmup because it is waiting for engine and O2 sensor(s) to heat up.)"

During this time (when the PCM is waiting for things to warm-up) is it in

open-loop??

Speaking of GM cats: Aren't they THE most free-flowing cats available? Can you

not see daylight right through one??

dewfpo · June 16, 2006

During this time (when the PCM is waiting for things to warm-up) is it in

open-loop??

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That's correct.

DEWFPO

Daubs · June 17, 2006

I've cut cats off older trucks (my 82 for example), but would never think of doing it on my newer vehicles. There is just too many computers controlling things...and when you remove one piece of the puzzle...well, the whole thing can go to crap really fast.