O2 windows, specifically on the 16197427 $0D

[PJG1173]

4940 Rich Idle O2 Voltage Threshold
4941 Lean Idle O2 Voltage Threshold

I've read on FSC.com about these can be used to adjust what afr the ecm thinks it seeing.

[RobertISaar]

I've read on FSC.com about these can be used to adjust what afr the ecm thinks it seeing.

you can use them to essentially change the target O2 mV where the ECM considers the rich/lean transition to be, i.e. Stoich.

some masks don't use single values though and use tables based on airflow/etc.

[EagleMark]

This brings up another parameter I have never changed. Stoich AFR! It's always set to 14.7 so if you changed it to 13.0 would O2 sesnor settings keep it there?

[RobertISaar]

bad idea to change it to anything other than the real stoich ratio of the fuel you're running.

reason being that the O2 sensor will adjust it back to the real stoich point when it does eventually add/subtract enough fuel to cause it to swing around the stoich calibration parameters.

so essentially, you would cause massive fuel trim issues. since the O2 sensor knows only lambda/stoich and doesn't care what fuel you're running, it will always transition from rich to lean or lean to rich when the fuel mixture transitions(assuming no odd things are happening, like fuel still combusting while passing the sensor, combusting AFTER the sensor, etc).

[EagleMark]

Then that brings up stoich ratio in fuels? Could they possibly be identical to fuel of 1987? Ethanol blends, some states have summer fuel and winter fuel... we have here now available 93 octane Non Ethanol!

I've seen some bins with 14.73 to 1 AFR. Is it still the same on todays OBDII cars?

[RobertISaar]

pretty much everything is within the range of 14.6-14.7:1....

and the ethanol blends? that's what the O2 sensor is for. GM knew back then that buyers would be switching between straight gasoline, E10 and everything in between. E15 is probably a stretch for a lot of cars, but it's still doable after tuning.

i made this a few years ago, but it may be useful... obviously, it's just a guide, but it's a hell of a starting point.

[EagleMark]

Cool! Is E10 what we see at the pumps that have I think it says 10% ethonal? Have you ever changed stioch and PE to these levels?

[PJG1173]

you can use them to essentially change the target O2 mV where the ECM considers the rich/lean transition to be, i.e. Stoich.

some masks don't use single values though and use tables based on airflow/etc.

yeah thats what the article said i just couldn't get my fingers to type what I was thinking. What I'm thinking is I can use these tables to basically recalibrate the O2 to compensate for the long tube hedders, or was I reading that article wrong?