O2 windows, specifically on the 16197427 $0D

[FSJ Guy]

Ok, so we got talking about O2 windows and then started hijacking another thread! :D

New thread time!

I found 4 tables for O2 windows:

Closed Loop @ 0x48F5
Open Loop @ 0x48F7
Closed Loop Idle @ 0x48F9
Open Loop Idle @ 48FB

The limits are all DIFFERENT! Some, not by much, however. The upper limits range from 677mV to 734 mV. The lower limits are from 278mV to 352 mV.

How much should I tighten them up to? Or, in what increments do you suggest I change them? I, too, think that swinging the AFR up and down is pretty silly. Seems like the motor would be happier with a constant AFR, not something that's zigzagging all over the place.

Thank you!

[gregs78cam]

I, too, think that swinging the AFR up and down is pretty silly. Seems like the motor would be happier with a constant AFR, not something that's zigzagging all over the place.


The thing is that the NBO2 is only accurate in a narrow band right around stoich. Hence the name. So the best signal the PCM could possibly have is one that goes rich to lean to rich just as fast as possible.

And here are a few more.

493D O2 mV Hysteresis for Rich/Lean
493E Minimum Slow O2 Error to Update INT
4940 Rich Idle O2 Voltage Threshold
4941 Lean Idle O2 Voltage Threshold
4942 Mean Rich/ Lean Idle O2 Voltage Threshold
4943 Proportional Duration Offset at Idle
4944 Proportional Duration Dead Band

The Idle PID parameters follow next.

Then a few more tables that deal with O2 and airflow starting at 4CD7.

[JeepsAndGuns]

Yea watching my innovate WB gauge while idleing, its jumping up and down a lot, never steady. I have been meaning to take a video of that thing and post it.

[PJG1173]

my WB and NB did the same thing at idle I reduced the idle spark error correction and that cut the bouncing around down alot. still swings all over the place while driving though.

[EagleMark]

There's a good read in the writeups on O2 sensors. It shows a bench test with volt meter and a propane tourch. Mentions readings as being lead fouled or silacone fouled as well.
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?82-Good-read-on-O2-sensors

[FSJ Guy]

And here are a few more.

493D O2 mV Hysteresis for Rich/Lean
493E Minimum Slow O2 Error to Update INT
4940 Rich Idle O2 Voltage Threshold
4941 Lean Idle O2 Voltage Threshold
4942 Mean Rich/ Lean Idle O2 Voltage Threshold
4943 Proportional Duration Offset at Idle
4944 Proportional Duration Dead Band

The Idle PID parameters follow next.

Then a few more tables that deal with O2 and airflow starting at 4CD7.

I can understand the window tables. But what about the above parameters?

IIRC, the value for the Hysteresis for Rich/Lean was set at zero.

[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?

[RobertISaar]

depends, i only try and fill at stations that i know have low/no levels of ethanol in their 87.

as for PE AFR, with E0(straight gasoline), i run an AFR of 12:1, which is close to the theoretical optimal point of 11.8:1 for E10.

i can't remember how A1 works ATM, but when going PE, if the BLM is north or south of 128(only one of them), it will auto-reset to 128 when entering PE and stay locked there until out of PE, when it will be allowed to move again. i should probably make sure that when above 128 that it won't auto-reset, otherwise when jumping into PE with ethanol-heavy fuel, while it works perfectly out of PE, it could go considerably leaner than i was anticipating since it would remove fuel.

[EagleMark]

There's a WOT locker program in the $EE information thread that locks BLM/INT to 128 during PE like your talking about. Way cool! I added 20% fuel to PE table and O2 right and O2 left stay around .900 during WOT!

[EagleMark]

Back to topic!!!

So if you have your tune close would there be any benifit to closing the gap of swing points?

[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?

[RobertISaar]

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?

that's entirely possible.


There's a WOT locker program in the $EE information thread that locks BLM/INT to 128 during PE like your talking about. Way cool! I added 20% fuel to PE table and O2 right and O2 left stay around .900 during WOT!

yeah, but what happens when you get a bad batch of gas(high ethanol) and to compensate for it the PCM has to drive the BLM up to 140 or so to maintain stoich in closed loop? that's 10% more fuel than what a BLM of 128 would deliver. then you go PE, it resets and instead of the 20% fuel added via the PE table, you only get 10%. now you're at a target AFR of ~13.2:1 instead of ~11.8.

[EagleMark]

Glad I set that up with the 93 non ethanol! I was actually trying to get some things worked out for last day at track to get a time but rained out last day of season... Now I've been just daily driving with no other changes to those type settings, I wonder what the O2 sensors would read with 10% ethanol enhanced fuel? Great, now I have to go do a WOT test! But I can't it's snowing...

You also got me thinking cause I ran a tank of 87 10% ethanol fuel and had to take out the four degrees timing I had added in there. I blamed it purely on octane, but it may have been stioch of fuel? Stock LT1 timing showed 1 degree retard from knock in a couple places, add 4 degrees and 93 non ethanol and no retard from knock.

Was going to add 4:56 gears and Nitrous too! :jfj:

But I may be pulling engine and trans for project or my Suburban and parting out the car. Dealer I got it from can't come up with title, filed complaint, he went out of business... got registration though? Don't know if I will ever own it? Can't sell it?

[RobertISaar]

could have been the E10's lower stoich ratio, could have been the lower octane, hard to tell without running E0 87 back to back with E10 87.

NORMALLY, you won't run into retard issues after the O2 sensor accounts for the fueling discrepency, since you'll then be running stoich at the same octane, but with that BLM locker stuff? hard to tell.