hey guys. i just recently bought an 87 with an S5 motor in it. to run the S5 motor and bigger turbo ect, the previous owner used a stand alone. im not familiar with the stand alones, ecu, harnesses for these cars so im not sure if it totally replaced the factory harness or what..., if i wanted to go back to factory specs, would i get an S5 or S4 harness and ECU? i would think S4 if the plugs ect sensors ect are still in the car from being an S4 chassis but being that the previous owner used a standalone im assuming all wiring is gone so i may be able to use either S4 or S5 harness?? please help! THANKS IN ADVANCE

 

http://www.rotaryresurrection.com/2n...o_s4_swap.html

You're likely missing the emissions (EM) harness. Some standalones use a replacement harness. The important thing to know is that the EM harness connects the ECU to most engine sensors, and it also connects to the front (F) harness. The front harness connects to many things behind the dash and around the driver-side of the engine bay. Browse through the S4 and S5 wiring diagrams to see the junction points: http://foxed.ca/foxed/index.php?page=rx7manual

The easiest way is to keep the wiring, ECU and sensors all S4 (AFM, MAP, TPS). Strip the S5 engine down to just a keg, and switch the front cover and TB with the S4 versions. You would be running the S4 mechanical MOP.

 

if it runs why would you want to go back to factory?