My Car Thinks Stoich is 15:1

[RevGTO]

Yep, multiple tuning experiments have proven it. I have played with VE and MAF calibrations and the only thing that changes is the LTFT's. No matter what I do, the logged AFR stays the same. I have gone from wildly negative to wildly positive LTFT's by altering the VE and MAF tables. But logged AFR stays around 15:1 while commanded is 14:63.

I don't really mind as I'm not running cats and being a little bit lean isn't going to hurt anything. But the net effects are that PE and lean cruise are off, so that I have to compensate by commanding richer AFR's than actual.

I thought that I had jacked my VE and MAF tables both so far out of whack that they were finding equilibrium at 15:1. But that theory didn't test out.

So I'm left with two theories: either the .cax files corrupted my tune so it wants to go lean, even when not commanded (unlikely), or that ethanol in the gas misleads the O2's regarding stoich.

Any opinions?

[5.7ute]

You will find that the fuel trims will trim until a stoich AFR (according to the narrowband sensors) is met when in closed loop, regardless of the fuel used. There is obviously a difference in what your wideband reports as stoich in comparison to your wideband.
What is B3601 set to?

[mr.prick]

What WBO2 are you using?
The pre-defined PIDs for all of the WBO2's are for the manufacturers stoich AFR and
that is almost always 14.7:1
Serial WBO2 is the same.

It maybe just a little bit of error between the calc_pid for AFR and commanded AFR.
If that's the case it's .03 AFR leaner than commanded not .07AFR leaner

[joecar]

Did you disable lean cruise, and do a full flash...?

[RevGTO]

B3601 is 14.63. I'll have to check my LM-1, but IIRC, stoich is 14.7 on there, so that could be a source of some of the discrepancy.

Lean cruise is not enabled; my current tune is built from one that has never had it enabled. But I have not done a full reflash with it.

[WeathermanShawn]

PE and lean cruise are off, so that I have to compensate by commanding richer AFR's than actual.

or that ethanol in the gas misleads the O2's regarding stoich.Any opinions?

RevGTO:

I thought you were running a lean cruise of sorts ( going from memory on your tune). I'm with Joe. I would make sure my B3605 is 'stock' and/or eliminate the EQ's <1.0 and make sure B3639 is all zero's. Then do a complete re-flash. I assume all your B3618 has EQ > 1.0?

I changed all my B4105 setting to 550mv. It just seemed to line up with an EQ of 1.0 (14.63 AFR) much better. Thats a thought.

My hunch is that it is still your wideband reading. I know you went through all the voltage offsets (another thread), but lately I have been glad I went with a serial connection through V2. Other than occasionally changing out the O2 sensor, it has all went flawlessly.

I believe the ethanol will change stoich more toward AFR values approaching 14.1 (10% ethanol). So it does not make sense it would swing you toward higher AFR's.

Just my thoughts. Good luck..

[mr.prick]

Ethanol in the gas won't change the AFR reading the sensor displays.
For serial WBO2 when stoich is seen it will display the AFR that it is programmed to show and for Lambda 1.00 and for analog it will depend on the calc_pid expression.

You can correct this by checking the Lambda value the WBO2 gives and multiplying it
by {B3601}.
Serial or analog?
If analog what is the analog output programmed to?

[joecar]

RevGTO, if you believe something got corrupted, do this sequence:
1. view all tables, make sure they're all sensible/sane and in-range.
2. full flash in a known good stock file for your PCM/OS/year/model.
3. cal-only flash in the file from 1. above.

Doing that will fix anything that may have gotten munged by an incorrect .cax definition.

[RevGTO]

RevGTO: I thought you were running a lean cruise of sorts ( going from memory on your tune). I'm with Joe. I would make sure my B3605 is 'stock' and/or eliminate the EQ's <1.0 and make sure B3639 is all zero's. Then do a complete re-flash. I assume all your B3618 has EQ > 1.0?

I changed all my B4105 setting to 550mv. It just seemed to line up with an EQ of 1.0 (14.63 AFR) much better. Thats a thought.

My hunch is that it is still your wideband reading. I know you went through all the voltage offsets (another thread), but lately I have been glad I went with a serial connection through V2. Other than occasionally changing out the O2 sensor, it has all went flawlessly.

1. I WAS running lean cruise ... this is one of the reasons I wanted to insure my AFR's were on target. Same thing with PE at the track. I had already edited all the tables you mentioned ... zeros in B3639, all cells in B3605 at stoich or below, except for a few that are 14.77, PE in mid to low 12's.

2. I have my nb's at 450mv ... that's what your tutorial suggests, but I've done that for a while ... I think AutoVE may recommend that. Do you now suggest 550, or is that a typo?

3. I think my wideband reading is good. Per the other thread, I knew it was off because logged consistently read leaner than metered. Since reprogramming, the logged and meter read exactly the same. I reset the stoich calibration to 14.6. We'll see if that makes a difference. This is V1 analog btw. All the specs can be found in the final post here: http://forum.efilive.com/showthread.php?t=13380&page=4

[WeathermanShawn]

No, I don't not recommend 550mv as the O2 voltage. I am only suggesting it as one way of manipulating stoich AFR. I also recommend that running the factory O2 settings are acceptable..they vary per airflow, and do include 550mv at the higher airflows.

I don't know what to say. My car runs at 14.63 AFR..so if someone else runs at 15.0..and they are 100% sure their wideband is totally accurate..I don't know what to say other than it is very unusual.

I guess you could change B3601 to 15.1 as your EQ and tune for that.

Other than trying another wideband..I guess you have to tune around your new stoich. Tough call. If it was me, I would go to a dyno or try another wideband.

Anybody have any ideas?