TPS/AFM?

[jondee86]

AFM contains a potentiometer to signal engine load (=airflow) to the ECU.
It also contains a switch to turn the fuel pump on, the idle air control and
(sometimes) the entering air temperature sensor.

TPS contains a potentiometer to signal throttle position, and contacts for
throttle closed (= idle) and throttle >70 deg open (= WOT or open loop).

The ECU uses the signals from both the AFM and the TPS to calculate
the mixture and ignition timing, accelerator pump function, fuel cut on
overrun, off-idle enrichment, hot and cold idle settings etc.

I believe it is possible to use the ECU to control ignition timing only, but
you will need to ask one of the Megasquirt gurus how this is done. The
other alternative is to use a distributor with built-in electronic advance,
such as is found on one of the K-Series (4K ?) engines.

Cheers... jondee86