IJCs in open loop/SD ?

[DrX]

Shouldn't the PCM be commanding identical IJCs for both banks when in open loop/SD mode. While they are usually close, but rarely identical, I am seeing differences of up to 13 points at WOT under boost(e.g. 66%/79% at 4000 RPM for a short period) How is this possible with no O2 feedback? This can't be good as my wideband only reports AFR from 1 bank.

[Tordne]

If you are running the V3 custom (which you must be for boost) and are commanding 14.63:1 AFR then you ill be in semi open loop, which will be trimming.

When in semi open loop is the only time I have seen the Injector Duty cycles different between banks.

[DrX]

If you are running the V3 custom (which you must be for boost) and are commanding 14.63:1 AFR then you ill be in semi open loop, which will be trimming.

When in semi open loop is the only time I have seen the Injector Duty cycles different between banks.

I don't have 14.63 entered anywhere except for PE(B3618) as per the tutorial. But I have normal PE disabled- I think(B3613 set to 285 kPa, B3616 set to 100%).

In B3647 all cells up to 85 kPa are set to 14.64 which still yields a commanded AFR of 14.73 for some reason. The 100 kPa column is all set at 11.8. As far as I know it should be in full open loop.

[DrX]

I also recall reading that the PCM will not go into open loop if there are any MAF DTCs set. As there is no way to prevent these DTCs, can this be what is causing the problem? Setting them to "non-emissions" still results in P0102 or P0103 being set. If I set them to "not reported" it results in a no-run condition unless I also plug in the disabled MAF, but then everything goes way lean??

It will run with the disabled MAF plugged in and the DTCs set to "non-emissions" but it does mess with the AutoVE logging even though the MAF doesn't appear to be reporting anything.

Everything is still set up as per the Custom OS and AutoVE tutorials and the MAF was unplugged when I logged the IJC differentials.

[Tordne]

Ross specifically altered the V3 custom OS's to operate in semi open loop when the commanded AFR = 14.629 (14.63) or the value in the {B3601} table if that tables exists in your OS.

This is specific only to the V3 Custom OS's and the only way to stop trimming occurring is to command an AFR that is different to 14.629 (14.63). I experimented briefly with changing the value in the {B3601} table. The only thing to remember if you try this is that all values the are calculated as an EQ of this value (PE for example) will also be affected.

Cheers,

[DrX]

Ross specifically altered the V3 custom OS's to operate in semi open loop when the commanded AFR = 14.629 (14.63) or the value in the {B3601} table if that tables exists in your OS.

This is specific only to the V3 Custom OS's and the only way to stop trimming occurring is to command an AFR that is different to 14.629 (14.63). I experimented briefly with changing the value in the {B3601} table. The only thing to remember if you try this is that all values the are calculated as an EQ of this value (PE for example) will also be affected.

Cheers,

No B3601 in my OS. I have been using 14.64 in B3647 with the intent of preventing going into semi-open loop. The actual "commanded AFR" seen with the Scan Tool is 14.73.

[Tordne]

So with no {B3601} 14.63 is assumed then. Try setting the AFR in {B3647} to 14.7. This is what I have mine set at and it also commands 14.73 in the scan tool, but definitely no trimming occurs. It may be that 14.64 is evaluated by the PCM as being too close to 14.63. If you were to change the display units to EQ you would find that it is probably the same number (just my guess).

[caver]

I am seeing differences of up to 13 points at WOT under boost(e.g. 66%/79% at 4000 RPM for a short period

The problem is at WOT when there is no feedback whatsoever.
Dont have a clue what the problem could be unless GM are expecting one bank to run leaner than another and are programming it to do that?.
Do log with the WB in one bank and then swap it to the other bank and see what the mixtures do.

[DrX]

unless GM are expecting one bank to run leaner than another and are programming it to do that?

I had considered that but most of the time the the IJCs are pretty close(the plot lines are coincident) with just the occasional divergence. If there was a programmed difference, I would expect it to be constant.

Does setting table B3618 all to 14.63 when AutoVE logging cause it to be ignored(i.e. 14.63=no enrichment)?

[caver]

I think so.
The idea is to run off b3605 to get commanded and actual the same.

[DrX]

So with no {B3601} 14.63 is assumed then. Try setting the AFR in {B3647} to 14.7. This is what I have mine set at and it also commands 14.73 in the scan tool, but definitely no trimming occurs. It may be that 14.64 is evaluated by the PCM as being too close to 14.63. If you were to change the display units to EQ you would find that it is probably the same number (just my guess).

Even with AFR set to 14.7 in B3647(reported commanded is 14.79) for MAP values up to 80kPa, I still see differing IJCs for Banks 1 & 2 when not at WOT. Either side can be higher or lower. Looks like trimming is active.

What's even stranger is that I am seeing this at WOT also.

I've gone through the tutorials multiple times and everything is set up correctly for open loop/SD.

With the MAF unplugged, LTFT/STFT and closed loop(temp) disabled, and no 14.63 values in B3647, what else could enable closed loop?

Could it be something to do with the custom OS/cal? Everything is up to date.

[Tordne]

OK,

Just check some other shit for me:

{B3801} = Disabled
{B4205} = Max temp
{B4101} = 0
{B4102} = 0
{B4103} = 0
{B4104} = 0
{B4108} = Disabled

All that is to ensure that no trimming is occurring. This is how I have my tune set (confirmed by Ross as being correct) and I don't see any evidence of trimming when not commanding 14.63.

[DrX]

OK,

Just check some other shit for me:

{B3801} = Disabled
{B4205} = Max temp
{B4101} = 0
{B4102} = 0
{B4103} = 0
{B4104} = 0
{B4108} = Disabled

All that is to ensure that no trimming is occurring. This is how I have my tune set (confirmed by Ross as being correct) and I don't see any evidence of trimming when not commanding 14.63.

B4101 to B4104 were still at the factory settings as I assumed that they would only affect idle. I can try changing them now that I know 0s are OK, but it doesn't seem that they would affect what's going on at part throttle and WOT.

Otherwise my settings are the same as yours including B0701=Disable and MAF disabled according to the tutorials.

[DrX]

Tried setting B3101-B4104 to 0"s. Doesn't seem to make much difference. Except that the first time I started it there was no ramp in to the commanded AFR. It went directly to 14.79. On subsequent starts the ramp in was active again. While the IJCs are identical at times, they still vary. Does everyone else see identical IJCs for both banks at all times in OL?

[DrX]

Could this be a data transmission issue? Just looked at a new log file and noticed at one point VSS goes from 3 to 39mph very abruptly. I wish that I had that kind of acceleration.

[Blacky]

What scan mode are you using? While logging press Ctrl+Y to display the "Profile window". It shows logging speed and scan mode. press Ctrl+Y to hide the Profile window again.

In the Properties window on the [Logging] tab page you can select the scan mode you want to use. Select Async 10x24 (soon to be renamed Stream-Fast) that should give you the most accurate scan data.

Unless you have a 98, then you should select Dynamic.

Regards
Paul

[DrX]

What scan mode are you using? While logging press Ctrl+Y to display the "Profile window". It shows logging speed and scan mode. press Ctrl+Y to hide the Profile window again.

In the Properties window on the [Logging] tab page you can select the scan mode you want to use. Select Async 10x24 (soon to be renamed Stream-Fast) that should give you the most accurate scan data.

Unless you have a 98, then you should select Dynamic.

Regards
Paul

Thanks, it was set to Asynch but I was using my 98 laptop. Will try again with my XP laptop tomorrow.

[DrX]

What scan mode are you using? While logging press Ctrl+Y to display the "Profile window". It shows logging speed and scan mode. press Ctrl+Y to hide the Profile window again.
Regards
Paul

So much for that theory. Didn't make any difference.

My next experiment was to disconnect the front O2 sensors. Worked like a charm. Both IJCs were always identical and the AutoVE process was getting things dialed in nicely.......until... I did a couple of reflashes and now I have differing IJC values on each bank again! They are close but no longer always identical. Experience tells me that if I attempt any further AutoVE tuning, it will make things worse, not better. I have even tried going back to the base tune that I started with after disconnecting the O2's and which seemed to work great. I am still seeing the non-identical IJCs.

The only DTC is still P0102 (MAF Sensor Circuit Low)

[Blacky]

When the INJDC differ, is it always the same one that is less than the other one? If so, try swapping the front O2 sensors from left to right to see if the INJDC follow the O2 sensors. It could be one O2 is calibrated slightly different to the other - or is getting lazy or old but not enough to throw a code yet.

Regards
Paul

[Blacky]

If that does not prodcue any results, swap the 4 injectors from one bank to the other bank. If the INJDC values "swap" with that change then it could be a faulty injector. The next problem would be to work out which one of the 4 is the problem.
Regards
Paul

[DrX]

When the INJDC differ, is it always the same one that is less than the other one? If so, try swapping the front O2 sensors from left to right to see if the INJDC follow the O2 sensors. It could be one O2 is calibrated slightly different to the other - or is getting lazy or old but not enough to throw a code yet.

Regards
Paul

No sometimes one side is higher, sometimes the other. The front O2 sensors are still not connected and the slightly divergent INJDCs have started up again. Worked fine for 2 or 3 logs right after I disconnected the O2 sensors. All O2 DTC enablers are set to non emissions.

It has to be in OL with the MAF and O2 sensors unplugged.

History/freeze frame data associated with P0102 says MAF airflow was 1.58g/s(the lowest value in the B5001 MAF calibration table). Should a MAF value be present at all with the MAF unplugged? Does it default to this if there is no signal?

[DrX]

Finally got around to bolting on my headers/ORY this W/E. No more O2s(fronts were already unplugged and all were "disabled" in the tune). Injector Duty Cycles are always identical again. Hope it sticks!

AutoVE seems to be working the way it was intended to now also.

Holy crap! What a difference. -18*C ambient air doesn't hurt either. Good thing our roads aren't iced over yet. No problem to smoke all 4 (more like 3) tires. Cleaned out all the junk in the little compartments on my dash on the 4WD launch. I see a 4l80E in my future.

Still have to deal with the fuel supply issue. INJDCs hit 100% at 5000 RPM and A/F starts to climb immediately. Looks like larger injectors with a properly sloped IFR table may be the only workable solution. Not sure how easy idle tuning will be though.