Mitsubishi ECU

[Joel A. Robinson]

On Thu, 9 Mar 1995, Peter Wales wrote:
> 
> 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.

You would know better than I, will the PCB of which you speak work with 
the 1984 Colt?  I know that the engines are very similar but I think 
there are differences between the computers.  As I understand it, the '84 
is unique, 85 & 86 had the same ECU and '87 & '88 had a newer computer 
without a boost driven fuel cut.  I think that the '87-on computer 
performs some other type of calculation like MAF > set maximum to protect 
the engine.  I really can't remember what I read, it was printed in a 
copy of Turbo and High Tech Performance that featured an '87 Colt Turbo 
with quite a few mods.  This article has been lost, God Damnit!

> 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.
My father has an '84 Colt Turbo with the '87 engine and ECU and I would 
estimate (no rolling road) he has 160+ horsepower.  His main performance 
gain came from having no trace of a Catalytic (parasitic) converter.  If 
I remember correctly, his car rarely exceeds 11 psi probably due to the 
microscopic turbo unit fitted to these cars.
 
> 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 am not familiar with the term 'zener'.  Would you mind drawing this 
unit up and emailing it to me?  I would certainly like to build the 
circuit you are talking about.

Why does the engine lean out?  Are the injectors maxxed out?  How could I 
keep the AF ratio correct at higher boost levels?  I have a little device 
that I ordered from JC Whitney (not exactly a world class performance 
outfit) that increases the injector pulse width and will allow up to 25% 
more fuel (if available of course) at an RPM starting point that you can 
set.  The problem is, it only works with single primary injector TBI units 
and mine has 2.  I guess this brings up another question:  How the hell do my 
injectors operate?  Are they like anti-aircraft guns that fire back and 
forth or is one really a primary injector?  No repair manual that I have 
come across specifies, they only tell you that they're injectors A & B.
   
> 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.

I would certainly be interested in a PCB!!!!  I would like to see the 
software too!  I can't believe that you exist!  No one ever has anything 
for these little cars.


> 
> 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.

Okay then, forget it.

My father has a Subaru Legacy 2.2L Turbo and I think I remember seeing a 
chip advertised for his car.  What does this chip do and what is required 
to get the horsepower rating that was listed?  I think it was around 250, 
a big jump from the extremely tame 160 HP it comes with.

Thank you very, very much for your help!

Joel Robinson
robinj at src.usbm.gov