Maybe we should do 2 more topics with "Idle entry conditions" and "Measures of good idle" ???
The first one seems interesting, the second seems obvious? For given engine temperature RPM and AFR are constant with a low standard deviation. You could additionally say that, without closed loop behaviour, it resisted changes in RPM due to load. Start the first one for sure! :-)
FWIW, I absolutely HATE modern engines, especially diesels, that try to maintain idle RPM under driveline load while lugging the engine. Horrible. And in some cases actually dangerous. Old dumb engines are MUCH nicer in such situations, especially if they behave well to low RPM levels. It's not uncommon for me to drag an engine down to 500 while in slow traffic then let it pull itself out again with light throttle before continuing to accelerate normally. It's OK for a driver to stall! That's THEIR fault!
There are just too many variables like alternator load, AC compressor on / off, atmospheric conditions and engine conditions.
Those things can be incorporated into the feed-forward value in some cases. eg, AC is typically turned on by the ECU AFTER the ECU ups idle speed/airflow.
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- the open source engine management systemFreeEMS dev diary
and its comments thread
and my turbo truck!n00bs
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