Mitsubishi ECU

[Peter Wales]

The early Mitsubishi ECU used  a Motorola 6803 processor base with some
extras in it which made it unobtainable. Typically of the Japanese, the
semiconductor sales people knew nothing about the mask programmed CPU, ask
the car people. The car people said we make cars not chips....go away.

A considerable amount of work allowed me to read the firmware and create a
pcb with an expansion port on it. This had the CPU, an EPROM and a port
expander chip connected to the CPU's multiplexed addrss/data lines. The
whole pcb plugged into a socket on the motherboard where the CPU used to be,
and the same pcb fitted the later Starion and the Colt cars available in
England in 1985 and on.

The fuelling on these cars is computed, not looked up from a table. This
made it very difficult to change because without knowing the full algorithm
changing one things altered others. My main concern was the removal of the
boost limit and this was less difficult. We ran the Colt cars at 15 PSI
boost without any problems (except massive torque steer) and as I remember
we got about 175 HP from the engine.

The way I would do it today would probably be with an FCD as it was too
expensive in engineering time to do it that way for the few sales we got. To
remove the boost limit, connect a 330ohm resistor in series with the boost
pressure sensor line, and a 4.3v zener to ground to clamp the input to a
maximum of about 4.5v. This will stop it cutting out, but when you get over
12 PSI boost the engine will start to lean out, so use your air fuel
moinitor. Ignition is controlled from a seperate unit.

I probably still have one or two of the pcbs lying around in England and you
may have one if you want one. If I don't have any and have to get them made,
I will sell them to you at my cost. Alternatively, I may even have the
original artwork and you can make your own. You can also have the software
as well.

Hooking a laptop upto this computer will be very difficult as you would have
to make an interface to convert all of the input signals to a digital format
and write the sofware to display them.

Let me know if you want any more info.

Peter Wales
Superchips Inc