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.