I sort of grasp that concept Stu - the BMW tach works on a frequency based system, the frequency which is generated by the ECU

Fuzzy on here with his E30 touring cosworth has the standard BMW revcounter working, but he isn't sure how its been done, as he paid someone else to do it

I need to start looking for ways and means of getting the tacho working, but i'm at a loss as-to where to start