I just got a good compression JDM Turbo engine and am ready to drop it into my 88 convertible. I used to race an ITS Rx-7 and this one has a lot into the suspension and interior and seems worth the trouble.
The engine (an S5) came without the ECU or the mass airflow sensor assembly, damn those hucksters. Do have the trans tho.
So the harness was cut at the ECU. Now I have to make the old NA harness meet the JDM Turbo engine and pray I can find an 89-91T ECU and MAFS.
I heard that the driveshaft from an automatic bolts in.
Can you fellow enthusiasts direct me to the right thread with all the info? I have seen some of it in fragments here and there posted. I guess I need the ECU plug also and solder it back on?
I did research all the other mods that are a good idea like porting the wastegate and the other usual snafus. But this harness I don't know.
I found the sections on the alternator wires, (thank you, Hailers) I'm just imagining that there will be sensors without wires to feed them etc. , or different plug configurations.
I see that its easiest to use my old NA harness and somehow fit the T2 ECU to it???

 

Mismatched engine/chassis swaps are such a pain, I don't know why people bother...

Keep the harness you have in the car, this will halve the work you have to do. Get an S4 TII ECU and plug it straight in. You'll need to make two small wiring changes at the ECU but nothing major. You'll also need an S4 TII AFM and MAP sensor to replace the NA ones. If you want to use an OMP you'll need to swap on an S4 TII front cover and TB, otherwise you'll have to premix.

That's as far as my memoroy goes for this post.

 

I did hear that version of the mod, you have to change the crank trigger with the timing cover and also the injectors. But what about things such as the knock sensor that don't have outs on the NA harness..
Thanks for the pics of how my car wil look, how bout some with the top down? And those wheels are perfect, I have the outdated looking oversize BBS wheels. But it really is the car they should have made. Any tips on my roof leaking? Only on one side near the curve of the roof I think. The rubber all looks ok.

 

I did hear that version of the mod, you have to change the crank trigger with the timing cover and also the injectors. But what about things such as the knock sensor that don't have outs on the NA harness..
Thanks for the pics of how my car wil look, how bout some with the top down? And those wheels are perfect, I have the outdated looking oversize BBS wheels. But it really is the car they should have made. Any tips on my roof leaking? Only on one side near the curve of the roof I think. The rubber all looks ok.
I gather from your post that the S4Turbo ecu will plug into the 88 na harness fine?

 

You need to change the front cover if you want a functioning OMP, but the CAS (which mounts in the front cover) is the same for all FC's and doesn't need to be changed. You don't need to change the injectors but you do need to cut the injector plugs off your S4 harness and replace them with the ones on the S5 harness.

If you're using the S4 TII ECU on an S4 NA harness there are only two differences that need to be addressed.

Pin 1R (LG/B wire) is the knock control unit on Turbos and the power steering pressure switch on NA's. If you're installing the Turbo knock control unit you'll need to cut the wire ~6" from the ECU connector and extend the connector side to where you've installed the knock control unit (which also needs power and ground connections). If you're not installing the knock control unit and you have power steering you'll need to cut the wire anyway, otherwise every time you turned the wheel the ECU would get what it thinks is a knock signal and retard the ignition timing.

Pin 2K (L/B wire) is the twin-scroll solenoid valve on turbos and the split air solenoid valve on NA's. In this case since your S5 doesn't have the twin-scroll system you don't have to do anything.

Note that all this info is easily found by studying the ECU info in the FSM Fuel Systems and Wiring Diagrams chapters. You need to be looking at this stuff now so you understand what you're doing. If you don't have the FSM, click here and download it in PDF format for free.

After six years I still haven't figured that out.

Correct, all ECU's of the same series are physically identical. Only the firmware inside is different.