A friend of mine bought this turbo timer and wanted to show me where he was mounting it. I noticed it had a readout for A/F and also O2 sensor voltage. Looking through the english version, it explains its O2 voltage to wideband A/F number. According to the manual, .96 is = 10.0 to 1, but the nut clencher is .94 is 12.0 to 1. Now I know the stock sensor sucks for tuning compared to the wideband, but why, in the past 6 plus years, of owning the PFS PMC, etc. the target number from Peter himself is .86 to be still considered safe and rich, but the Apexi guys seem to think .94 is still safe at 12.0 to 1, but anything lower is getting close to lean. Also, I know its not linear and the further away from stoich, the stock gauge gets more useless, but to go from way rich of 10.0 to 1 at .96 to safe at 12.0 to 1 is only .94, man thats nuts. Are they just off on the linearization of the stock O2 or is Peter off in his statements?

Any comments or ideas?

Tim Benton

 

Tim,

I had a PMS on my car for a while. The .86v was mentioned by all back then(about 1996). Most owners ran between .86 and .9 and did not blow their engines. I think Peter is more correct!

 

That's what I thought as well. Heck, I can't remember who it was, but one of the big list members, regular poster that was knowledgable, said with the bosch O2 sensor for the escort, he'd actually tune it down to .78 or so with it and he was still rich. Man thats been a while but I can't remember who it was. Trey, Trev, Brooks, Wael, crap, I can't remember.
I have that escort O2 sensor, but there's no way I'd go below .86, just to nerve racking. Unless I was tuning via wideband and was still 12 to 1 or richer and I just so happen to look at the O2 voltage and saw it was that low as well.
Tim Benton

 

I also use the ESCORT O2 sensor, and have my AFRs adjusted to the middle to high 11s from 4000 to 8000 rpm in forth. Maybe I should have a passenger check my PFC O2 voltage and see what it reads when under boost. Too bad the numers are so small on the menu that you can't read them yourself.

 

This seems like a good thread for me to relate a story. The previous owner of my 7 had a wire spliced into the O2 sensor which ran into the driver's side floorboard. It was no longer connected to any device, which I assume had been removed (this guy's electronics prowess was not stellar).

Well, I got the idea that I would hook my multimeter up to this wire so I could get a nice big temporary display of my O2 because I was gonna do some runs. I tested it at idle and with the multimeter off the reading on the Commander was 0.75. When I clicked the multimeter on the reading went to 0.67. This happened repeatedly (not always the same values). Well that scared me too much to do runs with it so I didn't use it at all. I may have had a bad ground on the multi, didn't have much time to fool with it.

Any opinions on this? Would other devices like an Autometer A/F gauge rob voltage from the sensor, thus making it less accurate?

-Scott

 

The O2 sensor output current is so low, that an average volt meter loads it down and thus drops the voltage. You will have to use a high impedance digital volt meter.

 

I have an APEXi auto timer and a PowerFC w/ the commander and most of the time, the O2 readings don't match even though the auto timer is just tapping into the same wire that's going into the PFC... I have my doubts about the accuracy of the O2 readings of that timer...