Rb25 Into R32 - Basic Guide

[predator]

Well my conversion has been finished for a few weeks. I did pretty much 100% of the work myself, with a bit of help from my flatmate in getting the engine in one day. It is not difficult, and I saved 1000's.

I will write up a more comprehensive guide to appear on my site soon (with photos), but for now I will just run down what I discovered. A few details I found when doing the conversion are not really mentioned in other threads on the topic so are covered here.

I also need to add, this is how *I* did the conversion. Others may have their own methods to do certain things, but all I can go on is how I did things and what I needed to do.

Special thanks to bhdave, bh_slo32, and others for the useful info in threads here and there on the various things that were required.

Engine removal

Pretty straight forward. Can be done in a couple of hours. No need to be a gun mechanic.

1. Remove the radiator and shroud totally for easier access (drain before-hand). Also recommend removing the clutch fan (engine fan), using 10mm spanner.. Just so there is a bit more room to bring the motor forward.

2. Remove all stuff on the top of the engine, cross over pipe, intercooler piping, and turbo heat shield (use 10mm spanner to get down there, fiddly). Remove passenger side rectangular block (fuel pump backup resistor).

3. Remove battery, to give a bit more room. Remove negative terminal from block. Follow negative lead to wear it bolts to block and remove there.

4. Remove bonnet and set aside. Requires 2x people.

Start on passenger side of motor. ..

5. Remove aircon belt and aircon compressor from block. 2 bolts bottom. One bold top I believe. Pull it aside, being careful not to puncture lines (if you have any gas).

6. Remove belt, and then remove power steering pump from block as one unit with all lines still together. You'll have to undo the tensioner, and the main lock bolt. Wiggle it back and forward on the bracket until it slips out.

7. Remove dump pipe totally from car. You may get away with leaving cat-back part still on car.

Switch to driver side area..

8. Remove starter motor wiring, noting / marking wiring position. Undo starter (difficult access). Remove first bolt from top, and remove bottom bolt. It's not too difficult with around 60cm of extenders stacked together, as can manuever with more room near the battery. Remove starter.

9. Not necessary to remove alternator, but can if you like. Remove wiring from back, note wiring.

10. Remove Oil pressure sender plug. Sender is metal can like thing near oil filter with rubber plug.

11. Remove the ecu from passenger foot well. Unplug ECU plug from ECU.. Remove ECCS and IGN relays (just unplug the tops) to allow easier pull through the firewall. In engine bay, remove foam access panel. Pretty much pull the loom, check for blockages, go back into the footwell, move it a little, back into engine bay, pull some more. Eventually it will come out. Leave engine/ecu loom ontop of engine. You may need to cut the factory cable ties to the firewall to get the loom free.

12. Jack up car at front. Get under engine and remove sump plug. Drain oil into pan. Recommended, as can be difficult / messy to do later.

13. Remove tailshaft.. bolts near diff. Center bearing bracket, and pull forward from gearbox. Set aside. Place oil pan near back of box (as now angled, gearbox oil will leak out the back of the box). Fit couple of plastic bags or similar over end of gearbox, using string or cable ties to keep oil from leaking out gearbox when lifted.

14. Support gearbox with second jack. Undo 4x bolts at gearbox mount. Use 14mm socket. Gradually lower jack to take weight of gearbox.

Remove RB20

15. Remove nuts for engine mounts (14mm socket). 1x nut at top, 1x nut at bottom on each side (there is one mount per side). The engine mounts are at the bottom of the motor, just in front of each of the strut towers.

16. Attach chains to back and front of engine. Secure around alternator bracket, or similar. Attach securely at back of the engine.

17. Angle engine forward, and lift out using engine crane. If you have a few people, you can use one to hold the correct angle of the motor and gearbox (and to manuever when on crane), and another to roll the whole car back. Makes it a bit easier. Lift crane back, and set engine down.

18. Sit rb20 next to rb25.

Transfer rb20det items to RB25

19. Remove block bracket for power steering. Transfer to rb25 (same bolt pattern)

20. Remove block bracket for aircon. Transfer to rb25 (same bolt pattern)

21. Transfer rb20 oil pressure sender to rb25. Unscrew rb20 oil pressure sender using 17mm spanner behind, and screw into rb25 block. Rb25 one may be the same, not sure. I used rb20 one (using r32 gauges after all).

21. Transfer clutch, gearbox etc to rb25 from rb20. You can use all rb20 gear if you like on the rb25 (including flywheel). Machine of flywheel recommended. Inspect clutch, replace if well worn (much easier to do now!).

22. Transfer starter and alternator to rb25. Rb20 stuff will work fine on Rb25.

23. Transfer engine mount bracket where bolts to block from RB20det (about 4x bolts on each side). Don't use rb25 mounts.

24. You can transfer rb20 exhaust manifold, all turbo lines and turbo to rb25 if not included on your rb25. They all fit and to me appear identical. You may have to bend the rb20 water feed line where it goes behind the block to get the correct angle on rb25.

This should be it.

RB25 engine installation

25. Dropping the engine in is as easy as dropping in an original engine. Angle inwards, using mates to get correct angle into transmission tunnel.. Another mate guides engine crane. Align engine, slowly dropping, make sure is aligned properly to engine mounts. Do it slowly until it aligns correctly with the mounts.

26. Reattach power steering pump, aircon to rb25

27. Reattach tailshaft. I had to use rear end of auto tailshaft, and front part of rb20 manual shaft (auto and manual are different splines/end bit) to get correct length. Standard rb20 tailshaft seemed about 3cm too long, and too long to fit diff with rb25 with rb20 box. You need the correct input spline to suit the gearbox you are using, rb20 manual end for rb20 box, rb25 end for rb25 box, etc.

28. Attach loom to rb25 and all sensors, feed ecu side through firewall to footwell.

29. Reattach body side loom to rb25 as per rb20. All gauges should work fine, starter should turn over engine, etc even without ecu hooked up. Starting car requires ECU to be hooked up though.

Misc things to note

1. I had to use rb25 accelerator cable, and custom bracket to move it forward. Cable is slightly longer than rb20 cable and is required or throttle will be constantly on (ouch)

2. Heater hoses are different diameter to rb20 ones. Can't reuse rb20 heater hoses. I used some aftermarket standard hose from engine side, cut rb20 standard hoses halfway across the firewall and joined via hose adapter, .. Or use rb25 factory hoses (these are around $60 each in 4 x pieces from nissan, ouch).

3. With rb20 gearbox, gearbox sits about 2cm further forward than standard. In mine, required cutting of rubber tunnel boot at top a little, to stop gearshifter popping out of gear. You'll see what I mean when you do it.

4. Don't use a twin plate or the like if you want your rb20 gearbox to last behind an rb25. Cushioned ceramic seems to work nicely at not putting too much straight on gearbox

5. Going from auto rb20 to manual rb20 box + rb25, I need a custom gearbox mount fabricated, as only 2x bolts line up.

6. I lost my speed sensitive steering. I believe this is due to a difference between the HICAS setup on r33 (electric) and r32 (hydraulic) and/or speedo. Or maybe it is just a wiring issue I didn't sort out correctly. I prefer the firmer steering anyhow.

7. If using rb20 box, just use standard r32 speedo cable to get speedo to work fine. Otherwise use the top r32/bottom r33 sensor method to rig up rb25 box. This adapts the electronic sender to the manual cable.

8. For temp gauge, the default temp sensor i had on my rb25 was slow to pickup the correct temp (although it may have been an aftermarket one). I swapped the one from rb20 and it fixed the problem. The gauge sensor is the skinnier one near the top radiator hose. The fatter one is the ECU sender.

9. I believe you can use a standard rb25 top radiator hose. Transfer bottom radiator hose to rb25. I ended up using an aussie R31 top radiator hose as the bend is the same, and cutting longer length side off to fit rb20 radiator.

10. You can use rb20 knock sensors and/or knock sub-loom, but you will need to cut the plug and wire directly into rb25 loom as end plug is different.

11. RB20det and rb25det coil packs are identical. Mix and match you better ones.

Wiring

Wiring is pretty straight forward if you have the correct diagrams and ecu pin outs. I'd recommend using the RB25 loom and ECU, which is what I used. This a) allows easy engineering to meet polution standards b) Allows you to run the cheaper and more readily available RB25 powerFC. Once you can get the stock ECU working fine, just drop in the PowerFc and it should work right away.

I won't go through the whole lot here, but a few things to note.

1. Grey wire near the main engine bay plug is your 12v constant injector feed. Make sure this is hooked up to a 12v line. Without this the car won't start.

2. It's not a bad idea to splice in your original engine bay resistor (passenger strut tower, silver block thing) from the rb20 loom back through the firewall and to the thick black and white wires of the r32 body loom. This provides backup ground to your fuel pump incase you lose the grounding in the boot area. It will work without it, but is a valuable safety measure which is worth keeping if you value the engine.

3. Use the O2 sensor from an RB25. I believe the R32 one is different. Effects fuel economy

4. To get the wipers working, you can use the r33 loom plug as a direct fit into your wiper.

There is another plug nearby which looks similar. You'll need to connect the orange in this plug as well or your wipers won't turn off once turned on until IGN is turned off Cut the orange up near the plug, and run a wire to this through the firewall, and this connects to one of the wider R32 body loom plugs. There is like a thick orange and a thick green next to each other. Connect this to the orange. This turns the wipers off when you whack the wiper switch back to "off". Took a while to work this out.

You also need to attach 12v IGN source to blue w/ red stripe on that plug. Hook the black with silver blotches to GND (or chasis).

The rest of the r33 plug is 'spare' and the other wires can be left disconnected down near the r33 ecu part of the loom as well.. On the R33 it connects to a brown junction box on the passenger side...but on the R32, this is on the driver side and can stay there.

[Dizmo]

excellent writeup predator. easy to understand. sounds easy makes me want to go do it to my 32. Any major problems u faced with the conversion?

[predator]

excellent writeup predator. easy to understand. sounds easy makes me want to go do it to my 32. Any major problems u faced with the conversion?

If you've got the money for the engine, you should be able to tackle it I've never done an engine swap before, if that's any indication. Engine crane was like $60 for an overnight hire so that's not expensive.

There weren't any major problems I guess. The main ones were the smaller ones listed in the "misc things to note", like working out what to do with the tailshaft, and then the heater hoses, and then the accelerator cable. I kind of came to them, and had to stop for a while to get the parts, etc. I didn't have much guidance on those, so just had to play it by ear as to what would work and use brain a bit I guess. The engine itself was easier than I thought.

The only other small problems were due to the guy I bought the engine doing some strange things with the hoses, etc so just having to get it back to as factory as possible by tracking down a few small parts. So it really depends on where you get the engine from, and those little small things that may be missing.

[=premo=]

need another one of these for an RB30det(t) install. everyone knows how to build an RB30de but no how to do wiring or bracket swaps and how well it goes into bay etc

[Krille]

Hi there i just got a car with this conversion started, the part thats not done is the wiring part inside the cupe, im using the RB25 ecu so that part is ok, but do i need to attach som cables from the other big white connector from the engine harness to some inside the car, i guess some are for the instrument panel?

[predator]

Krille: yeah... if you don't have basic electronics knowledge, best to leave it to an expert.

Basically you need to chop the big white connector.. that doesn't mate to the RB20 interior loom - which uses like about 4 small plugs. Also wiper wiring needs a few small changes and a few small things..

[CATKICKER]

Thanks for the writeup! I will be doing this to my car shortly (R32 - RB20DET 5sp)

Just thought it would be good to list parts needed and have people add/correct them so it can help me/others prepare themselves before starting the conversion.

This is what I have listed so far:

RB25DET Engine, loom and ECU

RB25DET O2 Sensor

RB25DET Accelerator Cable (modify bracket)

Radiator Hose (Can use and chop R31 Aus Spec)

Modify and replace heater hoses

Clutch Plate (if needed)

Machine Flywheel

I am looking at fitting my GTR Injectors and Z32 AFM to it but think it might be best waiting until it is in and running and I can't run them from the stock ECU.

Any further advise / suggestions / additions would be great!

I will add photos when I undertake my conversion!

Thanks,

Todd

[Krille]

ive completed this project, well almost something is still wrong, i cant get the car to run properbly when its warm, but according to diagnostics its the knock sensor so i will dig into that during winter.

but ive now got a RB25DET Neo engine in my R32GTS, along with the gearbox, after a couple of late nights digging into the wiring diagrams i got it working,and after some minor connections it works pretty good, except the warm thingy, problem i got when i was done was that the speedo didnt work, since this gearbox dont have any output for a wire, but along with the car camed a R34 dash, so i started modding to make it fit so now that is also sorted, this was pretty neat also since now i can use the built in diagnostic thingy that is in the ECU, oh and yes i also use the Ecu that camed with the engine

[CATKICKER]

Sweet, thanks for that! I am guessing you got it for a good price being an unfinished project, well done!

I can't wait to get started on this!

[lwboosted]

i have been talking with some friends about this and apparently you can still use the rb20 computer just need a remap.. anyone heard of this??

[cln]

^ you can but you wont be able to run vct

[Krille]

and if you use the Rb25Det neo computer it will save you on the fuel also i think

[subaueru]

The rest of the r33 plug is 'spare' and the other wires can be left disconnected down near the r33 ecu part of the loom as well.. On the R33 it connects to a brown junction box on the passenger side...but on the R32, this is on the driver side and can stay there.

Roughly how many wires become "spares" as you put, is there many?, because there's something like 40 wires on the rb25 end, and 42 on the r32 body loom between the four plugs. I've been having some major troubles finding wiring diagrams as all the links i am finding don't seem to work...

Also on the r32 body loom, what is the silver box that one of the 4 plugs goes into? Does it remain plugged in and all i worry about are the other three?

Any help would be soooo greatly appreciated!!

other then that, great writeup, very helpful, thanks!

[5LYDWAY5]

hey mate, what did you do with the belt? the harmonic balance is different. I got an r32 wreck and an rb32 silvia project. didnt come with p/s pump or a/c. was gonna use the 20 stuff but saw the differnce. what you do?

[5LYDWAY5]

hey mate, what did you do with the belt? the harmonic balance is different. I got an r32 wreck and an rb25 silvia project. didnt come with p/s pump or a/c. was gonna use the 20 stuff but saw the differnce. what you do?

[predator]

I've forgotten a lot of the wiring details sorry.. mine was auto, so it had a lot of wires going to the auto computer that I didn't need going to manual.

The engine I bought came with alternator belt, so didn't have to worry about that (I believe it's just same as rb20, the alternators are the same). AC belt is the same.. and power steering belt I just used the RB20 one. So basically from what I remember, use the RB20 ancillaries, and use the standard RB20 belts. If you do need slightly longer ones, the belts are fairly standard.. they're either 3 rib or 4, and can be obtained in a number of different lengths that fit other cars.

Aircon belt I used was Dayco 4PK0925

[Ryno]

Hey Predator,

I put a RB25DET into my R32 a couple of years ago, and I'm still ironing out electrical dramas. Does the R32 have an engine check light? As I'm keen to hook this up to enable 'knock warning' on my power FC.

Ryno

[predator]

I've got knock sensors connected up & they were working on my PowerFC when I had that installed? Did you trace these from the old loom to knock1 and knock2 pins on the rb25 ECU?

Not sure if the dash light warning for knock works or not, never tried it.. I did connect up engine check light wire to the ecu, so they should. AFAIK - knock comes from engine to ECU as incoming .. output of ECU goes to engine warning light on dash. If that sequence is fine, I would say the dash light should work for knock if you set it.

[PRO_32]

Awesome right up dude, good onya im sure alot op ppl have found this extremely useful.

One thing im wondering though is could you use the rb20 loom with minimal extra work ie; Will the plugs on the rb20 loom fit the sensors and such on the rb25 or conversly will the rb20 sensors fit the rb25..

Cheers...

[predator]

It can be done apparently but a few changes are required.

Your major difference is that the RB20det loom doesn't have VVT (or the) wiring.

RB20 to RB25 - CAS is different (but fits same plug), ignitor needs to be rewired as pins are different but plug fits. You'd need to swap over the CAS, and rewire the ignitor.

From memory I think wiring of two of the injectors is also swapped around. If you are using RB25 ECU with RB20 loom, other changes would be required as the pinouts vary in a couple of points.