Progress is slow, but there is progress. I found I made some mistakes in V1 of the board, first tried to add some wires:
But I found I make too many mistakes and there are board defaults for the clutch, fan, fuel pump and tacho signal. Besides that, I decided not to mess with the design of the alternator controller, I just fitted the alternator controller I bought
so that was done. That leaves me ample room on the PCB to fit the ULN2803 and the resistor, without messing with the original Speeduino board (which has no local 12V source on the experiment site). I just looped through the Arduino Pins to the Speeduino connector and put the ULN on the PCB. With that done, the PCB arrived last week and I installed all:
Nice and clean, the only two extra wires are from an LED driver of the wide band sensor controller. I abused some exhaust gas recirculation valve control wires for that, as that valve has been eliminated anyway.
So, still a lot to do on the car, but the ECU seems done. I have some PCBs left, if anyone is willing to try give me a should. It's not tested, yet.