There is a PID in my datalogs which I intentionally record, but I don't know when/if it is important, nor do I know how it is measured and with what sensor. I am speaking of course about the INTAKE MAN TEMP (Intake Manifold Temperature) PID. Does anyone know how this is even measured or by what sensor?
I know it is always higher than the IAT temp reading, except at startup in the mornings after cooling off all night. But once the engine is up to normal operating temperature, the manifold temp will consistently be 10-20F higher than the IAT temp, with summer time bringing the largest delta between the two.
I haven't found anything that says how that temp is used, what it might affect when calculated in, or what sensor provides the reading to the PCM. It's like it doesn't even exist...except that I know that it does because my data logs record its existence.
Surely I am not the first person to notice this black sheep of the PIDs and wonder what's up with it, am I?