O2 Sims

jagyro · 05-31-2006, 10:28 AM

hey all,

i was wondering right. When i install my full exhaust system would 02 sims protect the engine from running real lean? if so I'll just pick up a pair for the drive down to get the tune. Unless someone wants to let me borrow theirs

Doodad · 05-31-2006, 07:14 PM

If the GTOs are like the fbodys (and I suspect they are) the rear o2s only report their presence. Which is why you can sim them. It changes nothing except the computer report of emissions status. Needed to pass in other words because you throw codes.

jagyro · 06-01-2006, 01:13 AM

So i would take that as a. I will have to get it towed. damn even more of a pain.... thx

socal gto · 06-01-2006, 03:14 AM

If I heard correctly the o2 sensors that matter the most are the ones in front and not the back, so you shouldn't have any problems.

jagyro · 06-01-2006, 08:13 AM

i was hoping that with changing over to O2 sims it would help to not lean out my engine so i could get it to the dyno without worry of bad stuff happening

Doodad · 06-01-2006, 05:16 PM

I don't think you will have any problem. I know the fbodys (both LT and LS engines) ran pig rich. You should not run lean. When I did my full exhaust we had to lean and lean out the mix. Granted that was an LT1, but my friends experiences were similar. Other than smelling like gas you will survive.

bergenfelter · 06-01-2006, 08:16 PM

The front O2 sensors regulate the A/F ratio by changing the fuel injector pulse width, or the amount of fuel each injector sprays into the cylinder on each intake stroke. The front O2's are absolutely necessary, you cannot simulate them.

The rear O2 sensors can be simulated by a constant feedback voltage to the PCM. The feedback voltage needs to be pretty much steady state, so the PCM knows the cats are "working" and not following the same voltage variances the front O2 sensors see from the varying injector pulse width. This can be done by a mini voltage divider electronic gizmo plugged into the rear O2 sensor harness. I might have a couple that will fit the GTO, I'll need to verify, just PM me. Or, a cleaner method is to have the rear O2 detection programming removed from the PCM program.