[ncmncm]

About every microcontroller has hardware timer devices that can be set to trigger a signal change with N-nanosecond resolution (N from say 5-50), and even interrupt the core when it is done. The only sharply timing-sensitive bit would be ignition firing, so maybe control those with a hardware timer.

Thing is, you can use the whole repeating schedule, parameterized with adjustments to instantaneous RPM, for many cycles before there is need to check for e.g. throttle input changes.

In between, it is a dance -- shoot some fuel into 1, wait a bit, stop shooting fuel, wait a bit, start closing a valve, wait a bit, schedule a spark, wait a bit, ...

All the settings are chosen, whenever input changes, by table lookup. So tuning means fooling with table entries.