GM.DYNCYLAIR vs GM.DYNCYLAIR_DMA

[DrX]

Why would these differ if they are both calculated based on the VE table? (Speed density tune)

GM.DYNAIR - GM's estimated airflow in grams per second based on the VE table. This value is calculated independantly of the MAF. It is used to test MAF rationality and when the PCM is in speed density mode (i.e. MAF removed or disabled).

GM.DYNCYLAIR - GM's estimated airflow in grams per cylinder based on the GM.DYNAIR value.

GM.DYNCYLAIR_DMA - internal (DMA) PID that is used by the PCM as an index to look up various tables that are indexed on grams/second(??). This values is derived from the MAP, RPM, IAT and VE tables and is independant of the MAF.

[joecar]

I don't remember...

[DrX]

I don't remember...

Lol...My age group can relate to that.

[joecar]

lol

They should have the same values (or close), but they are conditions where they will be different...

but, from your other thread I think they should not be different and this is causing the problem...

so if we can find why they are different (may have to experiment with MAF and VE tables to further see how those pids are "influenced").

[GMPX]

Put me in the don't remember specifics group too.
The DMA PID would be a more accurate value as it is usually the final result from a specific routine in the ECM (pretty sure we chose the value used specifically by the spark table look ups). The normal non-DMA PID's will sometimes be filtered and scaled before being output to a scantool. However as Joe said the values should not differ too much.

[DrX]

Yes they only differ significantly during the rapid RPM increase/transition into boost. The same time my the throttle momentarily closing issue occurs. This issue seems to have started when I swapped in my other 80E and converter. This converter seems rather loose, stalling at 3800 rather than the spec'd 2600.