I am looking for the best place to mount the ECU on my MK Indy, but a little unsure as to where. I have considered inside above the passenger footwell, but means taking the wires through the bulkhead. Also considered mounting next to battery in the middle under the MK logo. Provided the ECU is grounded does it have to be mounted on a metal surface for heat problems. Any help gratefully accepted

John

Usually it does.... Especially if it has injector drivers in it....
Why not run the car with the ECU loose (but grounded) and see how hot it gets before fixing it finally in place.

If you are talking about the ignition amp then it is already on a heatsink and it is a good idea to place on a metal surface for further heat sinking. I remember when i took mine off the sierra it also had heat sink paste between the mounting surfaces. Not sure if the ECU is the same or not.

I used copper grease as heat sink paste - not sure if its suitable or not but seemed Ok for several K miles.