Testing Automotive ECUs

You are correct EFI is simple, more simple than ignition dwell and timing controls. The timer operations get complex when dwell extends prior to trigger events at high RPM. I find it easier to use two timer compare channels, than handle the complex cross-over in single timer compare activities. Speed is not typically an issue, ignition events happen at a few hundred Hertz max, the uC does 15 million instructions per second. A Bosch Motronic used an 8051, it is about 50 times slower than an Atmel AVR.