COS 5 alpha-n/tp ve with STFTs?

[Mud]

Not sure if this is a daft question, but I'm struggling to find an answer to it. Is it possible to use COS 5 in alpha-n mode (i.e. A0007 doing its thing) and still have STFTs?

[joecar]

Yes, you can, you can do either and/or both of these:
- run OL alpha-N, the stoich cells in B3647 would cause/allow STFT trimming;
- run CL alpha-N with LTFT disabled, this allows STFT trimming to operate during CL.

[joecar]

BTW: and in SD or alpha-N (i.e. MAF is intentionally failed/absent) the HO/LO adaptive spark mechanism still works (even if MAF DTC is present), this the COS's intent.

[Mud]

Thanks - I assume B3647 is a bit bodgey/coarse if alpha-n is necessitated by lack of a sane MAP signal (at least for certain engine conditions)...almost reverting to the 1D AFR as function of RPM vector (whose name I forget).

[joecar]

Yes, wherever MAP lands at, the higher MAP columns (i.e. closer to 100 kPa column)


( it would have been nice to have an RPM xTPS OL fueling table )

[joecar]

Much like the PE table, B3618.

[Mud]

That's the one I was trying to remember! :)

[Mud]

Possibly being daft again (chucked the MAF long ago) - can I use B0120 (RPM threshold for airflow calculation) to command MAF fueling for higher RPMs, then A0007 (TP VE) for low RPMs? I'm thinking perhaps a MAF would be advantageous for medium load conditions like climbing hills (vs. pure alpha-n).

I think I understand how the MAF is normally used (blended with SD as described below), but I'm not sure if the 'dynamically calculated airflow value' simply comes from A0007 (subject to whatever air modifiers the IAC imposes), or whether a bad/full-scale high MAP signal would stuff things. I'm thinking ITBs with a MAF reading off one cylinder bank, so MAP pretty meaningless above for most RPMs.

-------------------------
B0120 description:
If engine speed is less than this value, then the PCM uses a dynamically calculated airflow value to determine grams of air per cylinder.
While the airflow is in a "steady state", then a correction factor is updated based on the airflow difference between the MAF sensed airflow and the MAP calculated airflow.
During rapid changes in airflow, the correction factor is applied to the airflow calculations to compensate.

If engine speed is above this value, then the PCM will use the MAF sensor exclusively (if not disabled by DTCs) to calculate grams of air per cylinder.
No updates are made to the airflow correction factor.
-------------------------

I've related my current B0101 to what I think A0007 will look like by crunching some old data...I can describe this if there's any interest, but it's unproven and may be folly! I realise logging the VE table lookup value PID could go straight there, but I don't have any historic data for this.

[joecar]

B0120: this is the threshold above which PCM uses MAF-only, and below which PCM uses MAF for steady-state airflow and VE for transient airflow...

without MAF (i.e. MAF DTC present) then PCM uses VE-only (i.e. B0101 VE table).


If COS has A0003 TPSVE enabled, then when RPM, MAP, TPS are below A0004, A0005, A0006 respectively, then COS will use A0007 TPSVE instead of B0101 VE...

so when TPSVE is active, A0007 is used instead of B0101 in all the situations that would use VE (including transient airflow conditions when RPM is below B0120 when MAF is present).

[Mud]

Excellent, thanks :)