ECU

I have been pondering where to place the ECU. I have seen photos of all sorts of different mounts including low on the firewall, above the bulkhead in front of the scuttle and under the scuttle in the passenger footwell. The 2009 Focus ECU that I have is different to earlier Focus ECUs in that it uses three plug connectors rather than two, and these are on the top rather than on the back. They do however require a cable entry from the right. Also on the plus side, this ECU is considerably smaller, thinner and lighter. Given the Birkin chassis for the Duratec engine has a much deeper fusebox (cutting into the passenger footwell), I took some measurements and came to the conclusion I could mount the ECU in the bottom of the fusebox, below the fuse and relay frame. This position is good as I don't trust the dust seals on the connectors so I was skeptical about mounting the ECU in the engine bay. Ford obviously agree with me because the ECU came out of a heavily sealed plastic box in the Focus.

I started by putting the ECU in the footwell and positioning it for marking up the mounting holes.

From here I drilled through the footwell into the fusebox. To isolate any metal on metal vibration on the ECU, I lined the back of it with thin neoprene where it sat flat against the fusebox side. I also machined up some thin aluminum spreaders to use in the footwell rather than washers as the aluminum at the end of the footwell is quite thin so I wanted to spread the load out. I was able to connect up the rear harness connectors and lay these in the bottom of the fusebox before fitting the fuse and relay frame above it. This will make the relays and fuses easily accessible from the top of the fuse box.