No cats and still passing emissions testing!!

austin · #1 (**permalink**) 07-19-06, 09:52 PM

Is this true or BS.... Someone on another board installed headers and removed the cats, and then claimed to pass the emission testing by Purchasing a Diablosport Tuner and turning off the rear O2 sensors through the OBD-II.

StealthV · #2 (**permalink**) 07-19-06, 10:02 PM

If the emissions test is just to see if there are any active DTCs and that all tests have passed, then yes, passing emmissions is easily done by turning off the rear O2 codes. It's not Diablo specific - any tuning software will do it.

austin · #3 (**permalink**) 07-19-06, 10:09 PM

Thanks..

TXSilverV · #4 (**permalink**) 07-19-06, 10:49 PM

FYI! I just passed mine in Texas this week! No cats

atdeneve · #5 (**permalink**) 07-20-06, 10:57 AM

Roughly how much horsepower do you gain by going catless?

Does it increase sound levels at all?

trukk · #6 (**permalink**) 07-20-06, 03:50 PM

It definately increases the 'stink' level. You will definately smell the distinct odor of unburnt fuel. I don't think I could stand that.

-Chris

urbanski · #7 (**permalink**) 07-20-06, 04:14 PM

bah, this stink isnt so bad, you get used to it. hell all cars stink when starting up til the cats warm up. imagine that all the time...but you get used to it

2004ctsv · #8 (**permalink**) 07-20-06, 05:10 PM

If your car doesn't have a check engine light on during inspection then the tech may pass your car.
If you're in PA and they also lift your car to check brakes and they see that you removed your cats, you can be in for a nice fine.
If you log less than 5000 miles, you may get by without them pulling your wheels.

atdeneve · #9 (**permalink**) 07-21-06, 05:53 AM

Damn, I didn't even think about the fumes being an issue. I guess, that's definitely a factor to consider.

But, again, what really matters: Anyone know if going catless provides any horsepower gains and how much? Sound levels increased? Gratz.

1QUICKV · #10 (**permalink**) 07-27-06, 08:19 PM

I Just Want To Know About The Hp Gain? Do You Feel The Difference?

NoSlackCadillac · #11 (**permalink**) 07-29-06, 07:50 AM

Trips to the dyno in similar conditions, but nearly two weeks apart showed +13rwhp with the cats removed on a modified car.

atdeneve · #12 (**permalink**) 07-29-06, 08:18 AM

Wow, that is definitely a gain. I wasn't expecting that much from going catless, but I guess it does take out quite a bottleneck. Hmmm.

ewill3rd · #13 (**permalink**) 08-01-06, 05:34 PM

If cars can pass emissions tests without cats, why do carmakers spend billions on installing them?
Just curious... I think someone's pulling your leg.

I do think there are some operating conditions under which some of the readings may stay below the maximum limits, but a true dynomometer emissions inspection.... I seriously doubt it.

SoCadillac · #14 (**permalink**) 08-01-06, 06:01 PM

Quote:

Originally Posted by ewill3rd

If cars can pass emissions tests without cats, why do carmakers spend billions on installing them?
Just curious... I think someone's pulling your leg.

I do think there are some operating conditions under which some of the readings may stay below the maximum limits, but a true dynomometer emissions inspection.... I seriously doubt it.

California cars get a sniffer shoved up their tailpipe and engine rpm range run through for analysis. There is no way a CATless V would make through; unless someone did something under the able.

GotStroke? · #15 (**permalink**) 08-02-06, 02:44 AM

If an engine is running efficiently it doesn't need cats to pass emissions testing, this is true of all types of OEM engines. I've heard of a few random car owners that tack welded cat heat shields to their O/R exhaust in order to pass the visual.
Also having had an O/R pipe equipped car for over 7 years, yes it's louder and you mostly notice the fumes when the car isn't in motion such as at a stoplight, or when parked/idling.
As for the potential power gain, vs. the stock cats, I believe 13rwhp, but against 3" metallic substrates, no way.