does anyone know what will happen if my car has an 90 t2 engine with a 87 t2 ecu, will the car run good?

 

An 87 ECU is looking for low impedance secondary fuel injectors.
A 90 ECU is looking for high impedance secondary fuel injectors.

A way to test if the 87 ECU will work for your car is test the secondary injector's impedance. You can do this by removing the IC, throttle body and upper intake and testing the high outside injectors with a multimeter.
12-16 ohms is high impedance.
2-5 ohms is low impedance.
If you run high impedance injectors on an 87 ECU, you will burn the injectors.

I don't know if there is a difference between 88 and 90 ECU's, I would assume there is. I have an extra 88 T2 ECU (N333) that would possibly run your fuel injection, but I am not sure. I think the series 4 had two types of turbo computers (N332, N333) and series 5 had one (N???)

 

OK, I need to clear up a misconception here. All TII ECU's "see" high-impedance injectors. For those cars manufactured until June of 1987, low impedance injectors were used. In order to work correctly with the ECU, Mazda added a Solenoid Resistor Assy. - a metal covered set of 4 resistors with a 12V input, and an output from each resistor to each injector. This unit is in the passenger side front corner of the engine compartment under the air filter assy. If your car has one of these (I am assuming you are talking about an '87 chassis here), it is impossible to blow an ECU regardless of what injectors you are using. If your car does not have one of these, and someone for some unknown reason put low-impedance injectors into a '90 engine (Remember, everything made in '90 had high impedance injectors to start with), you could blow an ECU, but you would blow the '87, '88, '89, 90, and '91 ECU's - you get my point.

Having said that, and still assuming you have an '87 chassis here, you can get into a situation where the injectors will not work very well at all. On a car which has the solenoid resistor assy, if you try and run '90 injectors, you will end up with TOO MUCH impedance (Very High Impedance :p ). What you need to do in this situation is remove the solenoid resistor assy. from the car, and short the 5 wires going to it together. Then the injectors will be fine.

As far as the question about the '87 ECU running the '90 engine, it would be close if the '90 engine was a bare block, meaning that everything (manifolds, front covers, turbo, water pump assy, vacuum system) was bolted onto the new engine from the original '87. If you try it that way, I would get at least an A/F ratio meter, since the newer engine has higher compression and a lighter rotor assy.. Therefore, I am sure the fuel/ignition maps are not exactly the same. I haven't tried it, so there are no guarantees. Good luck.

Irv, Keith's dad