Proportional and Integral idle correction debacle

[Hib Halverson]

For a long time, I've wondered about a seemingly contradictory observation I have about the proportional and integral idle corrections.

With the proportional idle table.... [ECM] 12196 - Idle Proportional Airflow vs RPM Error. Proportional idle airflow adjustment. When Error RPM is negative (RPM high) then values are subtracted from idle airflow, Otherwise values are added...you can see that when the error is high, the table is reducing airflow...all is good.

Proportional.png

But when you look at the integral idle table....[ECM] 12195 - Idle Integral Airflow vs RPM Error. Integral idle airflow adjustment. When error RPM is negative (RPM high) then values are subtracted from idle aiflow, otherwise values are added...the graph shows the opposite happens when RPM error is high, that is: when the error is high, the table adds airflow which would seem to make the RPM error greater not less.

Integral.png

Has anyone else ever noticed that.

[hjtrbo]

Hard to answer accurately without knowing which form the GM PID equation is in. In the standard form, those values are fine as the P term will drive the direction of the result. But, in the standard form, P is usually expressed as a gain with the I and D as time constants. Hard to answer. If it works, just roll with it.

[Hib Halverson]

Thanks for replying