Badams932

I have an interesting build I’m hoping to get some insight with as electronics are not my strong suit.

First, the car/motor

-1990 1.6 body/trans

-engine 2000 eudm BP5A engine with a flat top intake and an NA8 alternator, turbocharged

-coils and fuel rail are off of the BP5A
(Running flow force 640s, thanks Nigel!)

-ECU DIYPNP that I took on a trade. I believe
its from a mustang but I’m hoping someone can confirm/help me finish switching to Miata. (See attached picture of main board)

I do not have the 1.6 motor or any components otherwise I would simply reuse the 1.6 CAS
and throttle body.

-more on the ECU. It is wired for sequential fueling and I would like to add sequential ignition (Toyota COPs waiting for Install) I believe in order to add sequential firing I need to jumper IG1-S1, IG2-S2, WLD-S3, and ALD-S-4.

In addition I believe I need to adds resistor to R14 and a diode to R5. (can someone advise which resistor/diode and confirm I need to add them)

The board is populated in a few other areas that I do not believe I will use. Can I leave them in place or should I remove them from the main board?

it is my intention to retain the crank sensor and cam sensor instead of purchasing a CAS, (Splice in to existing CAS harness) is there anything special I need to add to the board in order to accomplish this?

Im also hoping to do this with the throttle body wiring.

Any help is very appreciated. I have a newborn at home so my time to research is somewhat limited. Thanks for your patients!

Martin Y

Is the engine already installed in the car and wired in? If so, do you know what wiring mods were made?

It sounds like you have the original 1990 loom, so the DIYPNP would have to connect to those wires, but then the other end needs to be adapted to connect the 2000 sensors etc which will involve choices. The TPS, for example; the '90 wiring just uses throttle wide open and closed switches but the '00 engine has a variable TPS so you'll want to dedicate a wire to that signal.

One mod I will recommend for your DIYPNP is adding the jbperf PWM converter board to raise the drive frequency to the IAC valve. The original '90 ISC valve is content to be driven at a few tens of Hz but the later IAC valves really like to be driven at several hundred Hz to operate smoothly and quietly.

Badams932

the engine isn’t in the car yet, I’m planning on running a skunk 2 throttle body on a square top manifold
and modifying the existing harness to the 2000 sensors. I actually have a few questions about that as well. I know the 2000 fuel injector harness that is on the motor is wired for sequential injection and the megasquirt is set up for it, but will I need to modify the 90 main harness to plug into the 2000 injector sub harness?

I would like to run Toyota COP for firing and have the megasquirt also set up for that now but everything I’m reading modify’s 1.6 components. I have the 1990 main harness but 2000 coil packs, what do I need to change/purchase to run COPs?

here’s where im at with the engine,

thanks for the help

Martin Y

Yeah, you will. That question at least I can answer. The '90 ECU used batch injection and only ran two wires to the four injectors; a yellow wire on pin 2U drove injectors 1 & 3 together and a yellow/black wire on 2V drove 2 & 4.

https://www.miataforumz.com/1990-200...ing/90diag.pdf