DIM Electronic Advance Ignition

Kit,

You have a good understanding of the complexities. Some variables have a fairly minor effect and/or a simple algebraic equation can manage them, with no input from the User. The effect of IAT on required fuel flow is an example. The Megasquirt manual shows how they use a fixed equation to account for IAT (I recall). Users need more simplicity, which is why self-tuning controllers are so popular.

I have designed controls in engineering for decades. Open-loop control is termed "feed-forward". Ideally, the equations (predictors) adjust the outputs (fuel flow, spark timing) so the desired setpoints are hit directly (desired O/F ratio, max spark lead w/o pinging). Of course, that is never perfect, due to unmeasured variables (camshaft & valves, exact displacement, gasoline quality, fuel pressure & temperature), so one uses feedback (O2 sensor, knock sensor) to move exactly to the setpoint.

In our cars the factory designed only crude mechanical feedforward controls - accelerator pump, vacuum secondaries or air valve (4bbl carbs), centrifugal and vacuum spark advance. The only feedback is very slow - owner adjusts distributor to the ping limit, changes jets and rod distances, and such. Electronics are much better, but not simple or cheap. It does seem they could be cheaper though. We saw a promise of that in the RabidGator spark controller, but I have yet to see an actual product. Megasquirt had the promise of cheap, but reality is ~$500 and much installation effort.