I've been getting quite a few PM's asking for wiring info for RB20->S13. So I'll just post it up here.

This how-to is for 89-90 240SXs that came equipped with SOHC engines. Wiring up a 91-94 DOHC engine should be very similar, but not quite the same. This how-to also assumes that you already have the engine and tranny installed. If you are performing this swap, make sure you have the engine and tranny installed properly.

1) Run the ECU harness into the passenger side of the car, extending the mass air flow sensor, and O2 sensor wires.

2) Locate 2 plugs on the RB20 motor harness. Both being rectangle and one having 6 wires, and the other having 8 wires.

3) After locating these, find the female end of each of these plugs and cut them back about 6-8 inches.

4) Locate 2 oval plugs on the KA chassis harness, one being grey, and the other being brown.

5) After finding these, cut the Black/red wire, and connect it to the Black/red wire on the RB plug that was just cut.

6) On that same plug, cut the Red wire and splice it to the white/black wire on the same RB plug.

7) Going towards the fuse box, there will be a white wire that goes into the box. Cut and strip both ends of it.

8) Splice the white/purple wire from the RB plug into the white wire.

9) Off of the ECU there is a Black/pink wire for the fuel pump, run a wire from the ECU into the engine bay to the black/pink wire from the fuse box.

10) Now there will be a plug with 2 wires in it on the KA chassis harness, one being white and the other being black/yellow. Find the black/white wire on the other RB plug and connect the two.

11) Coming out of the fuse box there will be a plug that contains a small white/red wire. Take that and connect it to the white red wire coming from the RB motor harness by the alternator.

12) Take the thick white/blue wire and run a wire from there to the positive battery terminal; that will charge the battery from the alternator. The way I did mine was I took the RB battery harness and connected it to the battery as well as the KA battery harness, that way it powers the KA harness and the RB harness, same goes for the negative battery cable.

13) Make sure to use the ground for the starter from the KA lower harness.

 

Right ON! Is this the same for an RB25 swap?

 

Definately not. The wiring for the R32 is alot like the 240, it has all it's main power stuff in the harness in the motor bay leading to the fuse block, where the 25 has it going into a main plug that goes to the ECU then out into the bay(someone correct me if I'm wrong, I very well may be).

 

Is that everything that I need to do? So both ecu's will be in the car? If you could give me a little more info that would be great.

 

NO ONLY ONE ECU WILL BE USED.... THE RB20 ONE.


TRICK #1: USE ONLY THE KA LOWER HARNESS. CUT THE STARTER AND ALTERNATOR PLUGS OFF THE KA HARNESS AND SPLICE THE RB PLUGS ON TO IT. THE REST OF THE HARNESS IS THE SAME MINUS THE OIL PRESSURE SWITCH WHICH ALL IT REALLY IS..... IS A LIGHT. THIS ALSO ALLOWS YOU TO USE THE STOCK SPEEDO AS LONG AS YOU USE THE KA SPEED SENSOR.

 

I have a question for you Nismo421. I'm doing a RB20 swap right now. I only have 1 square plug, the only other one that's free plugged into the windshield wiper motor(I got a clip and gutted it myself). I was just looking at the R32 GTR swap we have in stock and it has 2 square plugs right together, kinda at the end of the harness. I've already tested the plugs wires and found that 3 are constant +, one is switched +(stays on after IGN2), and the other 2 are for the A/C switch and P/S sensor. I'm also running the KA lower harness like projectrb240.
???????????

 

I know this is an old thread, but I guess my question falls in this category, is the wiring for a 240 with hud and digital speedo any different? Thanks

 

no, should al lbe the same. Those difference are in the dash, no in the engine wiring.

 

Does anyone know the differences when wiring the 91-94 DOHC, thanks !!!