Rb25 Into R32

[JordansR32]

Hi guys as the title says im putting a rb25 in my 32. I tried searching but couldnt find the answers i needed. I want to use the series1 motor coz i have been told its the easiet and thats what i want, as ill still be using the rb20 loom.

Now i have been told that the series 1 rb25 will use the rb20 ifnitor module and coilpacks and will plug straight in using the s1 rb25 motor, and i have heard the afm is different, wont be a issue coz im running a adaptonic.

Or the other option was the s2 rb25, which dont run the ignitor all done threw the coilpacks, so what has to be done to still to the loom to make the works, and im sure there are other different parts to the motor.

If you could give me some info or links that would be much appreciated.

[phatlavish]

The series 1 rb25 AFM & rb20 afm are the same (5 pins, green sticker), but the series 2 is different (3 pins, pink sticker) and will need re-wiring

You can also use the rb20 coilpacks on a S1 rb25, they're the same - If you're gonna use the rb20 loom you can just keep the whole ignition setup. if you were using the rb25 engine loom you'd have to use the rb25 ignitor & coil loom as the plugs for the ignitor are a different size (slightly smaller if I remember right)

[JordansR32]

Yer i wont be using the afm anyway, im not running one. Think im going to go the s2 motor keeping the 20 loom, so i wont need to change to much?

[Traah221]

Well, I guess you're in luck seeing as how I just did this conversion myself.

I opted to go for a Series I RB25, since it is closer to the same style as the RB20. I kept the RB20 loom, hooked to the RB25 ECU. RB20 Loom to a series 2 ignition system is just begging for a whole mess of problems since the two are completely incompatible. The Series 2 has individual ignitor chips in each coil pack, so you would have to do some crafty wiring to make it work with the Rb20 Loom.

Now, the reason I used the RB20 loom was because it is almost plug-and-play. What needs swapped over are the Injector plugs. The Rb20 has Top-feed injectors, while the 25 has Side-feeds. So, just chop off the injector plugs from a 25 loom (all 6 will be on their own sub-harness under the intake) and solder them in place of the ones on your RB20 loom (3 will be on the main loom itself, 3 will be on a sub-loom under the intake). If you copy my setup, this is all the wiring fabrication necessary, easy as pie.

There are a few things to note on this conversion that I ran into.

-Use an RB20 Ignitor and Coil pack loom, this is a must because the RB20 and RB25 ignitors have opposite configurations, the Rb20 ignitor has a 6-pin feed from the ECU, and a 7-pin feed to the coil pack loom, while the RB25 one is exactly opposite. Obviously, this won't work with an RB20 Loom in that case.

-The heater hoses hardlines will be much larger on the RB25 block than what comes from the R32's heater core. I don't have any solid fix for this, I happened to get lucky at a hardware store and find a brass pipe fitting that I could clamp on to both hoses respectively to join them. Some people get joiners made, so maybe look into that?

-The throttle cable on the R32 is just a slight bit shorter than the R33, so if mounted as-is, the throttle will be open to about 2500 RPM at idle. Two ways to fix this, either nab an R33 throttle cable from a nearby wrecker, or do a little drilling on the metal bracket that secures the throttle cable to move it forward on the intake about half an inch or so.

-RB20 gearbox mounts right up the the Rb25, so no worries. It probably won't last behind that thing for very long though.

-Motor mounts and starter need to be swapped over to the RB25 once both engines are out, mounts are different, and the starter was just personal preference, so, not really a "Need".

-Still not sure how to deal with power steering setup, you should try keeping the RB25 power steering pump, or getting one to put on, because the pulley on the crank for it is a 2 valley pulley, while the pulley for an Rb20 Power steering pump (what I have) is a 3 valley. If you put the RB20 pump on, the RB25 belt will not fit, and the RB20 Belt will hang partway off the Crank pulley, so, your call.

-Have to use R33 radiator hoses, R32 ones will not work. Again, wrecker is probably your best bet.

-On the IACV, the Rb25 has a different setup from the RB20, so don't be alarmed if you can't find a mate for the purple plug on it. The brown plug actually controls your IACV, while the purple plug is meant for controlling airflow when running A/C. This isn't a problem since, well, the RB20 never had this in the first place, so your R32 won't notice a difference.

-I would highly recommend swapping over the wastegate on your Rb20 turbo to the RB25. The RB20 wastegate actuates at just a wee bit higher amount of boost, allowing more airflow, and giving you a free couple PSI with no risks.

Lastly, enjoy this conversion. It will breathe new life into the R32 GTS-t that you didn't know these old girls could do, it has been an absolute blast and I haven't even begun to build her yet. Any other questions or hiccups, feel free to give me a shout!

Have Fun, and Good Luck!

[StevenCJR31]

heater hose mismatch easily fixed by changing the metal inlet/ outlet fittings on the block to the ones on the 20

[StevenCJR31]

heater hose mismatch easily fixed by changing the metal inlet/ outlet fittings on the block to the ones on the 20