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MS43 ECU with M54-powered BMW E30

Practical Motorsport Wiring - Club Level

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Has anyone experience with MS43 ECUs with M54-powered BMWs?

I'm starting afresh wiring an M54 into an E30 which has had the entire original wiring harness removed. Almost all of the M54->E30 conversions use harness adapters into the existing E30 loom, which does not really help me. Also I'm considering discarding the standard BMW relays and fuses and replacing them with relays and fuses in a Bussmann/GEP/Littlefuse PDM.

If I am correct, the stock MS43 ECU receives switched +12V power from S2 Ignition switch (Fuse F29) to pin 26 X60004 (see M54_MS43.png). The ECU also receives permanent power from the terminal 30/B+ to pin 7 X60001. Pin 23 X60002 is the signal to activate the DME relay and the DME relay supplies power to pin 8 X60001 (F2).

BTW F2 also supplies power to the DISA solenoid valve, VANOS valves and IACV. F3 supplies power to the MAF, Cam/crank sensors, e-Thermostat and coil circuit of the fuel pump relay. F1 ignition coils, F4 O2 sensors amongst other things not needed and F5 injection relay.

If I were to keep the original fuses and relays, I think I would need to supply switched power to the A2076 B+ potential distributor highlighted in yellow.

I could mirror the standard power supply using four EFI relays and switched power to pin 26 X60004 and permanent power to pin 7 X60001 as per E30_M54_Power_Supply.png. A race car may not need this. A simpler option could be to provide switched +12V directly to pin 8 X60001. Will either of these work?

BTW I’m leaning towards the GEP 72 position PDM which has more that enough space for 4 relays and 8 fuses.

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