We have been talking about automotive compters in school the last few days. like all the sensors and stuff what the should read etc... I got to thinking, what do O2 sims till the computer?? Do they use readings from other sensors and tell the PCM something based on those readings. or do they just give a generic reading that tells the PM things are reading fine and in spec. Thanks guys.

 

All they do is lie to the PCM.

 

Thanks. But im more intrested in HOW they lie to the PCM. Like do they just give the PCM a flat reading right at 14.7:1 A/F?? Or do they actually tell the PCM based on other sensors in the car. Cause unless they actually give the computer some values that are based on what the engine is doing then im going to keep running cats, because quit frankly ODBII is a damn good thing.

Thanks.

 

My understanding is all they do is confirm that they are operational, and consequently the cats must be operating properly.

 

Sounds like you may be thinking they replace the front O2 sensors. The sims can only be used on the rear sensors, who's only purpose is to return a signal that can be compared to the front sensors to see if the cats are working. So the front sensors are the ones the computer's using to manage your a/f, the rears aren't used for any actual engine management. The sims are hooked to no other sensors, and simply send back a generic O2 signal that the PCM reads to determine that yes, your cats are actually working.

But if you're considering removing cats, my vote is not to do it. Sounds worse, smells worse, not much value unless there's some other reason you don't want cats....

Dave

 

O2 sims don't give a constant signal to the PCM if that's what you're wondering. I've watched the values with my scanning software and the mv value jumps around, not nearly as much as the front O2's do though.

 

I knew they replaced the rears, but i had which senors did what. So what you guys make sense, i just got a litte mixed up.

I woundnt be removing the cats for a while, until i go with a true duel setup. But i may end up keeping them on for sound level reasons(and so i have somebackpressure).

 

Sorry, I am trying to step on this thread. But, where do you buy o2 sims and how much are they?

 

Go to www.tbyrne.com or www.thunderracing.com