i'm thinking of replacing my cats and slp y-pipe with an ory. i'm guessing i'll need o2 sims, but would like like to know how it goes about doing its job. i'm particullarly concerned about a simulated signal giving my pcm information that will make my car run worse, negating any gains that i might pick up from the loss of the cats.

thanks in advance...

 

The sims have two functions: to give a 450 mV signal to the PCM (= cats are OK) and to adsorb the power usually used to heat the O2 sensors.
Sims won't hurt at all.

 

i have an add on to this "?"... is it possible to remove the cat and see any kind of gain without replacing the 02 sensor with an 02 sim? and are any o2 sims out there any better than the others? main reason im asking is i had a nearly free flowing exhuast on my x-firebird no cat no o2 sims and it basically ran like a stock if not worse than a stock bird, would 02 sims have made a difference? (im considering removing the cat on my LT1 but this has bothered me since i saw o2 sims mentioned). thx for any answers in advance

 

I believe if you remove the cats on OBD-2 you either have to reprogram the pcm or use 2 O2 sims for the rear O2 sensors.

 

Yes, you have to use sims (are all the same) or reprogram the PCM.
You should have a code if you remove the cats.
What do you mean with "free flowing exaust"? Headers + catback?
Without any other mod they won't give you that much power... other mods = heads, cam, stroker, N2O, blower...
My suggestion: leave the exhaust alone and save your money for other serious mods. The exhaust is to get the max of the other mods and for the sound.

 

i gained a half a second from headers and removal of cats i have no o2 sims so i get a SES light but it still got me a half second on my formula

 

Actually the O2 sims I have seen actually have an ocilator in them. If you look at them in EFIlive. It's not a flat line, it's a square wave. This is cause the PCM is looking for the switching of the O2. If it sits at the same level, it will thow a code. I have found a couple bad ones and this was the problem, they weren't switching.

 

Good information, Dark Angel!

 

I don't understand why you would want to remove your oxygen sensor?

If your buying an exhaust without O2 sensor bungs just buy the cheapo $5-$10 weld-on sensor bung and be done with it.

The O2 sensor detects how rich or lean your engine is running and adjusts it accordingly. Even if you are only intending to run at full-throttle only, do your really want to be telling your car that your not? This doesn't make sense, many people are replacing their stock O2 sensor with wide band sensors to increase the sensitivety not eliminate it.

 

the rear 02 sensors are only there to test the converter. They have NO function for controling fuel trim. There needs to be a correct deley from switcing when compared to the front 02's this tells the computer that the converter is not flowing too much (where they switch at the same rate) if the computer sees bias voltage ( 450Mv) they it will set a no activity code. The computer needs to see the rear 02 switching or you get a catylyst efficiency code. The sim is just that. a simulator. it mimics the signal to the computer as a properly working cat/02 would and this will not set a code. You only need to worry about sims on an OBDII compliant vehicle. anything without a rear 02 you can cut, gut, **** on etc the cat and the computer will not know the difference.


Also as a note. NEVER EVER EVER put an 02 sim on a front 02 sensor. This is bad bad bad and yes, I have seen where people have done it. Sims are ONLY for the rear

 

Whide band instead of the front O2's?
I think they give different signals as the stock sensors. I would say additionals wide band.
Some heated wide band sensors can be put at the end of the exhaust.