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Found A Easy Way To Do A R32 Rb25 Conversion

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Hey guys,

After many hours scouring the interweb on everything for a R32 into RB25 conversion I have found a site with some very useful information.

As most of us know the RB20 and RB25 ecu pinouts is the same except for the Injector 4 and 6 pins. This site is saying that all you need to do is use the RB20 Engine Loom, swap the two injector wires over, and the plugs for the injectors and then you pretty much just plug the RB25 ECU in and your pretty much good to go.

All that would be left is the VCT which by the looks of the wiring schematic for the RB25 would just need the plug from a RB25 loom and wire the 2 wires in.

Can anyone confirm if this would work? I have been thinking about it long and hard and cant find any reason it wouldnt seeings the pinouts are basically the same.

If it does then it would make one hell of an easy conversion, as there would be no need to splice looms and everything would plug straight in.

I have heard of people using the RB20 loom and ECU, but not the RB20 Loom and Rb25 ECU...

Any input appreciated :)

Here is the site:


And heres the DIY from the site:

Well, there seems to be a certain amount of confusing regarding wiring when doing the RB20 -> RB25 swap.

I read quite a few conflicting things in my search for accurate information, and at the end of the day i just looked over the wiring diagrams, and plugs on the harness, and used little bits of information i read.

So with that, i'm going to post everything you need to do (which is really not much at all). swapping from rb20 to 25 is about the easiest wiring swap you could possibly do. This makes swapping a SR20 into a 240sx look like rocket science.

We will be using the RB20 harness, as its 100x easier, and has no downsides.

You will need:

-Complete RB20 harness including injector sub harness

-RB25 injector sub harness.

- (optional) a plug that will fit onto the VVT solenoid, and some wire.

1) Take the injector sub harness off the RB25. This is the one with the plugs for the sidefeed injectors.

2) Cut all the plugs off, leaving enough wire to solder them onto the rb20 harness.

3) cut off all the top feed plugs on the RB20 harness. 3 are on the sub harness, and 3 are on the main harness.

4) Solder the sidefeed injector plugs onto the RB20 harness and sub harness.

5) You must swap the wires for injectors 4 & 6. Doing this at the ECU is the easiest Just cut pin 112 & 114 and cross them and resolder.

If you have an afermarket ecu (such as in the case of this install), and you can configure your outputs, you can do this in software. In our case we used an AEM EMS... its nice because it supports the RB20, 25, and 26 with one unit.

6) If you want your VVT to work, you must get a hold of the right connector for the VVT solenoid. If you have an rb25 harness, thats easy just take it from there, if not take a trip up to the wreakers and snag one off some random nissan that will work.

Then just solder 2 wires to it, plug it into the solenoid, and wire it up into the ecu. We didnt hook it up, so i'm not sure on the exact wiring. I do know pin 113 is a trigger for the VVT. It would be easy to figure out with a wiring schematic. If you need help with this, post a schematic that includes the VVT solenoid on it, and i'll tell you how to wire it.

7) Your done. Make sure you use an RB25 ecu or calibration.

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a mate of mine told me he ran a rb20 ecu in his car (ceffy running rb25) when he was trying to sort out a fault and he didn't alter any of the wiring and it ran fine (he's generally not one to bullshit)

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Yeh there are a lot of people running rb25s with rb20 looms and ecus as the rb20 ecus are easy to reprogram.

I'm interested to hear if people can think running the rb25 with the rb20 loom but the rb25 ecu would work as the wiring looms are basically the same. Which would mean no need to splice the looms

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Use rb20 computer and loom with a nistune and it is even easier.

this. you just lose a little bit of low to mid range power from not having the VCT. if you use a z32 ecu though you can keep the VCT. just need to do a little bit of splicing.

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Then it's not really any easier. I was just thinking If someone was to do a conversion it would be easy if you only had to swap over a couple wires and your running. Then you could do the nistune on the rb20 later down the track. I think a lot of people find the hardest part of this conversion the wiring

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um how is that not easier you don't change ANYTHING on the ecu side, you don't even change a 'couple of wires' they ALL stay the same lol.

The msd switch or eboost is seperate, you just run 2 wires to the relay, 2 to power and 1 to RPM input off the ECU.

It doesn't get any easier than that haha

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