I decided that it would be an awful hack to use the MC1 fuel/ignition computer and wiring with 034efi since there would be a lot of wasted wire and sensors in the engine bay.

My solution was to completely remove the MC-1 wiring and instead use ONLY the ignition side of a CIS III wiring harness. The reason this is possible is because CIS 3 has 2 completely discrete ECUs. One for fuel. One for ignition.

To acomplish this project I bought a complete 80 quattro parts car so I could salvage the harness, sensors, and computer. I actually ended up using a harness that my good friend Huw Powell had in storage with the promise of returning the one that is in my parts car to him once I strip it. He ends up making out on this deal since my parts car is a 1992 and has the updated electrical system which means sealing boots on all engine bay connectors....

After looking at the diagram for the harness in the Bentley, I realized that there were at least three wires which interfaced directly between the ingition and fuel comptuers. This worried me somewhat until I got confirmation from other listers that with 034 EFI connected, they were able to disconnect the CIS fuel computer and the car still ran. Reassured with this information I discovered that one of the wires is a potentiometer input to the ignition computer which compensates timing under load. 034EFI provides an output to drive this (driven off of MAP). One of the other wires is merely an indicator to the fuel computer that an ignition related fault has occured. Interestingly enough this can actually be used as a knock light.. albeit a limited one. The light illuminates when the ECU hits full retard from knock (which isn't a good thing).

While I can't claim complete victory yet as the car isn't ready to test fire for the first time, I can show you what I have accomplished so far... See this section of my image gallery.