Have a friend who removed his catalytic converter in his Trooper. It backfires very little and the growl is not too loud at all. What would be the negative consequences of removing catalytic converter? (other than fines/tickets etcetera) Loss of torque? 02 sensor wreck havoc?

well, besides the obvious of being illegal and hurting your ability to pass emissions testing....

too much flow results in loss of backpressure which can hurt your low end.

If you have post 96 OBD-2, this will screw with your O2 readings that are after the cat.

-Rob

Thanks for the reply. My mistake, should have mentioned it is a 1991 V6.

Is it possible to pass emissions without a cat? i've heard different stories on this. there is stuff you can buy at autozone thats call like "garrented to pass" it says if you don't pass then they'll give you your money back or something like that. but thats probably asuming you have all of your factory equipment. i was just wondering if something like that might work.

In Georgia, you pay $25 bucks to get emissions.
If it doesn't pass, you have one chance to fix it. If it doesn't pass again on the second time, you pay another $25 bucks the third time. "Guaranteed to pass or your money back"... yeah, they give you your money back, but your car still doesn't pass emissions and you pay to have it certified again. Unless you are running an alternative fuel, I guarantee you it won't pass without a converter.
You can dump some methanol in the tank before taking it and it will help... but they will fail it if it runs "too clean" also..

Yes, i've seen it before, but i wouldn't count on it. Odds are more likely you won't. if you originally came equiped with a cat, its supposed to be there as part of the visual test. But here in NC, i've seen friends pass with gutted cats.

-Rob

Yeah, they use a mirror to check if you have them. If they are gutted and your emissions are OK otherwise you will pass. There is no way for them to check if it actually works or not unless they take temp readings which I never seen done. Obviously if you dont have a cat at all you will fail.

<img src="/forums/images/graemlins/shame.gif" alt="" /> If you knew how much cleaner your emissions are with a cat versus without, you wouldn't even consider going without. Maybe you are too young to remember what the smog used to be like... <img src="/forums/images/graemlins/barf.gif" alt="" />

Those of us who breathe thank you.

I agree, and for what purpose are you removing the cat? performance? the performance gain, if any at all, on our engines and what we do won't be noticable.

-Rob

I had an argument a while ago with couple of members on this board, so before this thread gets ugly i would like to say that the gains will not be even noticeble (if any at all).
Last time i was stating otherwise, but since i was forced to cut my muffler out completley (one of the damages in Uwharrie) there's actualy quite noticeble los in low-end toque & power. Yes sure when the engine revvs at 4500-5000rpm it has more juice, but at lower rpm's i deffinatley lost it.

Just my $.02

rubo