Microtech Noob Really Needs Help!
 

Here’s a post from a real Microtech Noob. I bought a ’93 RX7 (in non-running condition) this fall which has a Microtech LT10s/X4 and I am debating whether to replace the ECU with a Power FC. I am trying to figure out what was done when this one was installed (person who did the install has left town) which will then also help me figure out what has to be undone if I decide to replace it. But regardless if it stays or I pull it – I would really like to know what was done and was it done correctly. I apologize if this is information I should know or can readily find out. I have searched and read applicable threads back several years with little success. So here goes –

I have posted 4 diagrams I made showing the 4 yellow connectors and their inputs/outputs which go into the stock ECU. I realize the Microtech has it’s own “harness”. And I assume the installer basically intercepts wires (thermosensors, crank angle sensors, etc.) and ties them into the Microtech harness. And I guess that a lot of the stuff which is not used by the Microtech (emissions, sequential turbo system, various brake, clutch switches, etc. are simply not hooked up). But isn’t there some stuff which the old ECU controlled and is still needed? There doesn’t appear to be an installation book which specifically addresses this stuff (or at least I haven’t been able to find one). So here is where I need the help from you guys.

What do you do about the Oil Metering Pump? Just run premix? Use Rotary Aviation’s replacement system? Does RA’s unit vary the amount of oil injected based on throttle position? I read where Microtech has a “plug and play” adapter which will run it but I don’t think I have that. Or at least I can’t find it anywhere.

What now controls the radiator fans? There are several fan relays which depending on the engine temperature and whether A.C. is on are told by the stock ECU to turn on in different combinations.

I guess there is a tach ouput off of the Microtech so that shouldn’t be an issue. Although I have read a lot of posts about tachs not working. Mine does, I think.

And I guess there is a means to hook up the A.C. using one of the Aux inputs and then adding fuel at idle (or increase idle rpm). Need to explore that one more. There are a couple of good threads which talk about A.C. in this section.

There is a white connector and a blue connector on the stock harness (cabin side) which I believe connect to the dash and or instrument cluster (haven’t figured this one out yet). Isn’t it true these must remain to supply data to instruments, etc.? Which I guess means the existing harness must remain in place.

I realize I have asked a lot of questions, but if anyone could just answer even one of two of these questions maybe between several of you I can get this sorted out.

I have been told that the Microtech is just “ignition timing and fuel” and that looks like it pretty much sums it up. So how do you keep the other stuff going?

Thanks,

Jeff

By the way, maybe someone can make use of the connector diagrams. The Mazda wiring manual sure has been difficult for me to interpret. I didn’t mark the outputs to the coils – didn’t know which ones they are.

The microtech isnt a very good computer for an FD..

But in your car case the car has been butchered already to fit it.

So if you wanted to go powerfc youll need a new engine harness.

I do recommend you make the change back to powerfc, as the microtech controls nothing else but injectors and spark.

Thank you for the reply and the recommendation. I agree, ultimately I would like to have the PowerFC running the car. I have an engine and emissions harness which I am going through and checking/repairing. But I am afraid it won't be as simple as just replacing the harness. The previous owner has "modified" the system powering the fuel pump, the cooling fans run as soon as I turn the key "ON", and who knows what else yet. Has a turbo timer and a AVCR boost controller which may also affect the systems. I am in the process of pulling the motor for a rebuild (blown seal I think) so maybe some of this will become more clear when I have everything disconnected from the Microtech and see what I really have.

The car ran well with the Microtech, I don't want to change too much at one time so I plan on getting it running again with that ECU and then make changes later.

Just thought I would offer the pin out diagrams I made and try to get other's opinions on some of the questions I asked.

As far as i have tried, never have been able to get the tacho wiring.

The FD was a very complicated car and the microtech wasnt broad enough to do everything.
In saying that, if the car is running well. Then dont play with it too much.

If your factory computer is still their, everything should be working fairly descent.
Depends on what the standard computer still picks up changes what it does.

Thank you for the reply. The factory computer was removed but I have one I could put in it's place. Is it possible to run both computers? This might solve some problems but there are some sensors like the Throttle Position Sensor which would have to go to both computers. Doesn't the TPS feed info to the stock ECU so that it knows how much oil to inject based on rpms?

I'll have to trace the tach wiring because my tach is working with the Microtech.

As i said in another thread my tach works with my LT-8. but i used the harness adapter