Open/closed loop

**c5z28** · 08-01-2010, 11:06 PM

Can anyone explain it for a newb? Was talking with someone about open/closed loop who had tuning software and told him about my o2's being cut. I guess they call that open loop. I know the car runs rich since I smogged it for giggles and would like to verify putting my o2's back on (and a new tune I guess)will cure that. My car won't pass visual but with cats and only bolt-ons it should still pass the sniffer. My car got to 1500ppm and they shut it down because it just wasn't going to pass.

**0rion** · 08-01-2010, 11:16 PM

In a nutshell the front O2's "close" the loop and the pcm uses feedback from them to determine fueling. That's the one sentence version.

Do you have a specific question about it?

**c5z28** · 08-01-2010, 11:20 PM

I don't like the idea of my car running on a closed table(not sure if that's the word or open is the word). I don't see how my car with cats and only being bolt-ons could have failed so miserably.
I guess a pertinent question would be: is there any benefit to running an open loop? Does the maf even do anything if the o2's are closed?

**0rion** · 08-01-2010, 11:26 PM

yes, the MAF still functions in open or closed loop. You have to tune it to speed density to get rid of the MAF. You're correct though, with your limited mods I would keep your O2's (closed loop).

**c5z28** · 08-01-2010, 11:40 PM

I know it's late so feel free to sleep on this one. Is there any actual benefit to running an open loop for those who are more modified? Seems like it would be track based rather than meant for street driving.

**Frost** · 08-02-2010, 05:00 AM

Only the ability to run leaded fuel (since it kills O2s and cats).

You NEED your front O2s. You gas mileage will come back when you fix them as well.

**c5z28** · 08-02-2010, 02:27 PM

Originally Posted by Frost

Only the ability to run leaded fuel (since it kills O2s and cats).

You NEED your front O2s. You gas mileage will come back when you fix them as well.

Well my tuner tuned them out, I didn't ask him to he just did. And I can smell gas when it runs so I guess the problem isn't necessarily the high flow magnaflow cats. Good to know thanks for the wisdom.