Afm > map

[aurace]

have been playing with a euro spec e30 318is m42.  Have currently got an aem piggyback and MAP sensor and am trying to replicate the original AFM signal.  

What i have found is that the AFM signal will vary depending on the engine temperature - which makes replicating it with a map sensor very hard.

Can anyone confirm this is what the stock AFM does? eg: Cold engine at idle ~ 800rpm AFm will read 1.2v .  However when hot - 800rpm, same Load it will read 0.8v

is this what the little blue resistor in the afm does?

[DesktopDave]

I know that there is a thermistor built in...I'd assume you're right about it varying the voltage curve.  I have no idea what it'd look like though.

There is a very wide variety of cars that ran this Motronic system, I'm sure that information is out there somewhere.  OpenECU.org perhaps?

I'd suspect you're also going to see some really wide variations on 20 year old AFM units.  Even Bosch can't make something that works perfectly for that long.