RB25DET R32 GTS-t conversion advice needed

[Remix-]

Hi, I am soon to be undergoing an RB25DET engine + RB25DET Gearbox conversion into my R32 GTS-t. Any detailed advice relating to my following questions would be greatly appreciated!

1. What needs to be done to the tailshaft and gearbox cross member? I have heard the tailshaft needs to be shorted (does anyone have any specifcations on how short?) and that the gearbox cross member needs to be modified? (specifics would be great).

2. I plan to use the RB25DET wiring loom and RB25DET standard ECU to maintain simplicity until it is running. What complications can i expect to face using the RB25DET wiring loom with the r32 gts-t? I have heard such things as the Speedo will not work etc..

3. Does the harmonic balancer need to be changed?

Responses to this thread are appreciated! I have gone through the searches on RB25DET conversion, but there is really no detailed information in relation to wiring and ECU's. I hope this thread will clear that up and possibly help someone else doing this conversion in the future.

Cheers

[Cubes]

It won't start on the std. RB20DET ECU unless you use the injectors from the RB20DET.

I've recently dropped a RB30DET in to my R32. That used the R32 RB25DE head as I was able to bolt up the RB20DET plenum to the RB25DE inlet manifold. In turn I was able to use all of the RB20DET's sensors/injectors/cas etc.

The RB30DET starts and drives fine with the RB20DET ECU.

BUT.. always a but.. Boost is a problem. It tends to run really lean when coming on to boost then goes really rich once its on boost.

I've wired the wastegate wide open so it doesn't make boost.

Can I ask how much this RB25DET engine is costing you?

It may work out close $$ wise to building up a R32 RB25DE with a set of forged pistons.

Then for a similiar price you have a motor that will be able to make 300rwkw without the worry of cracking ring lands. + the best part about it is the RB25DET sitting under the bonnet will look exactly the same as the RB20DET.

Then get your self a S1 R33 RB25DET gearbox and bolt it up. Modify the cross member to suit and you will be fine.

I have heard a roumer from SDU that the R32 Automatic Cross member will bolt up to the RB25DET gearbox perfectly.

The only problem is getting your hands on a Auto cross member.

The RB25 head is definately the way to go.

Comparing the RB20 valves side by side to the RB25 valves the rb20's look like little piddly toy's. The RB25 inlet valves are 5mm bigger each. So thats an extra ~10mm over both valves.

[Remix-]

Would it be more worth while to use the RB25DET entire wiring loom? Along with an RB25DET ecu (eg, i could use Power FC for RB25DET)?

Or as an alternative would it probably make more sense to get the entire car wired up with brand new sensors using a Wolf V4 ECU?

The entire RB20DET engine has been sold, bar the radiator, ecu and standard wiring loom.

I have an R33 GTS25t half cut on the way, so basically i was hoping to use everything from the half cut that i could.

[Cubes]

You would have to use the rb25det ecu. And possibly the wiring loom.

Quite a few ppls have done this conversion so the wiring loom question can be answered easily.

[Remix-]

Now im really starting to get confused. I know of a fellow on here, Starion Turbo who is using an RB20DET standard ECU that has been rom'd in his R32 GTS-t with RB25DET in it. My question is, What wiring loom is he using? Standard RB20DET wiring or RB25DET wiring?

[MerlinTheHapyPig]

i beilieve you'll have problems using the R33 wiring loom with all of the R32 ancillaries - i don't know for sure coz i haven't done the swap b4, but most people keep the R32 loom and re-wire it into the R33 ECU.

Re-wiring the R32 loom is the hardest thing - you might want to employ an autoelectrician that has done it before rather than stuffing around yourself.

There have been a few topics covering this sorta swap, and a few people have done it b4, (i hate to sound like a whingy dickhead by saying this - but do a search and see what u come up with!!)

[Remix-]

So what your saying is that i can use the RB20 loom, and rewire the original loom to the R33 harness to the chosen R33 ECU? Why couldnt i use the standard RB20DET ECU wiring and harness and have it ROMed to suit the RB25 injectors?

I have done a few searches and have not found much in regards to wiring up the engine. As I am not giving this in to a workshop to do, I need to learn as much as possible.

Thanks guys

[Cubes]

The reason why is the R33 RB25DET has a slightly different pin out on the ecu.

So simply plugging in a RB25DET in to the RB20DET wiring harness 'may' make some thing go crisp. Even though I doubt it..

Nothing is ever simple.

Your best bet would to start reading the R32 and R33 engine manuals that are floating around. They have wiring diagrams and ecu pinouts.

You would also have to wire in something to handle the R33's VCT.

I worked out the cost of a RB25DET 1.5years ago and the cost of a rebuilt std Rb30E bottom end. + the R32 RB25 head. I allowed 2k for the bottom end rebuild and 1k for the head. All up the total cost only just nudged over 3k for a RB30DET conversion that wouldn't require stuffing around with wiring looms and a motor that didn't look stock sitting in the engine bay.

So.. I went the RB30DET route but got carried away with the engine rebuild and ended up spending close to 4k on just the bottom end + 1k in porting/polishing of the head.

So a 3k motor turned in to a 6k motor

[predator]

Really depends how you want to go.. to save hassles I think you're best off using the rb25 loom and say a PowerFC or stock r33 ecu. Otherwise all I can see is unforseen extras and work arounds by trying to use the rb20det ecu/loom. Seeing as you're getting a half-cut, you're already going to get those bits you need, why stuff around with it?

As I picked up an RB25det complete for $1600, my original plan for RB30DET went out, even though I had most things ready. ~$5k+ vs $1600... hmm.. and later on I have the rb30 bottom end ready to be rebuilt when the time is right. It made no financial sense to go straight to rb30det.

What do you want? a true monster in a fully rebuilt rb30det (don't forget you're going to need the matching $ turbo to do that).. or an rb25det that still has torque advantages, still is a great motor, and probably still good for 250rwkw. You will probably have the cash left over for a nice turbo / injectors / PFC on that as well, whereas after the rb30 build, you still have to factor in all the extra things. I had an R33 for nearly 2 years, the engine was great - unbeatable.. it was just the rest of the car I was bored and a little frustrated with.

Engineering an RB25DET shouldn't be so difficult, as long as you maintain exactly the same engine, and this will mean the same stock ECU and most other things. As there is no such thing from factory as "RB30DET" its going to be much harder.

With the tailshaft, really what you're going to have to do is take your existing rb20 one, and from what I read an RB25 one (different input splines?), work out how long it has to be once its in the car, and go from there. That's what I'll be doing.

When I do the conversion into mine I will post full pics and step by step instructions as I learn along the way.

I have heard a roumer from SDU that the R32 Automatic Cross member will bolt up to the RB25DET gearbox perfectly. The only problem is getting your hands on a Auto cross member.

Guess I will be testing this then

[Cubes]

Make sure you let me know.

This RB20t g/box isn't going to hold up too long.

[Remix-]

predator, what wiring loom and ECU do you intend to use for your RB25DET conversion? What do you intend to do with the ancillaries? Swap to an RB25 dash?

[predator]

rb25det loom, and stock ecu... got it with the engine. Just to get it working and for the first month or so.. then powerFC when I wind up the power...

For the dash use the standard speedo sender mod (electronic bottom, mechanical top). Auto-electrician can sort out the rest or will see how I can go. I know a bit about wiring and electronics which might be enough - there are fragments of this and that around on here and elsewhere.

For anciliaries such as aircon, power steering, and starter going to be trying to use these items off the rb20det. Aircon could prove problematic but we'll see.

[Remix-]

It would be great if we could compile a list in this forum of all the things that need to be changed and worked on in an R32 GTS-t when using an RB25DET wiring loom.

[MerlinTheHapyPig]

yeah, i think there is definantly a need for a tutorial for this swap, as lots of people have done it, and there isnt' much info on the forum about it.

(I will be doing the swap myself, but not for some time (the car isnt' even in australia yet!!!) and when I do, i'll take lots of pictures and try to put together a tutorial.)

[Guest]

yeah, i think there is definantly a need for a tutorial for this swap, as lots of people have done it, and there isnt' much info on the forum about it.

(I will be doing the swap myself, but not for some time (the car isnt' even in australia yet!!!) and when I do, i'll take lots of pictures and try to put together a tutorial.)

I will be watching this post with great interest too as I am planning this swap in the near future too.

[MR R32]

I also have plans to do this conversion, just waiting on the engine to arrive from Japan... Its becoming very popular.

[Remix-]

So what other problems could i possibly expect to face using the RB25DET wiring loom?

[JH32]

Hi, I am soon to be undergoing an RB25DET engine + RB25DET Gearbox conversion into my R32 GTS-t.

Good shit dude !

A mate of mine did this conversion into his R32 ... if you want his number PM me I'm sure he'd give you any help you need. Either that or he'd do the conversion for you.

[GTR-Ben]

I just did the RB25DET engine conversion, on my own in 2 days... it is really quite simple..

Not the box.. but the only problem there is the speedo. Just use a mechanical one and modify the sender to accept the cable.

use the RB25DET loom and ECU.

RB20 Power Steering and mount to block

RB20 Alternator and side loom. Just need to pull apart the RB25 side loom and remove the wires for the knock sensors. etc

Use the RB20 engine cross member, engine mount brackets and engine mounts.

Heater hoses need to have an adaptor to reduce them to rb20 size.

Wiring, to get the car running you have to run 3 wires into the engine bay from under the dash from the RB25DET SMJ.

I forget the colours off my head, but I can tell people if they ask..

Basically

To be continued... got to go sorry guys

[BHDave]

I'm in the process of doing this at the moment. I'm sticking with the rb25 ecu and engine loom and using the rb20 loom to the starter, alternator and oil pressure sender. The rb25 has the egr valve under the plenum so runs into the loom running down the drivers side chassis rail and the knock sensors do too. Luckily both simply strip out of that loom and plug straight back into the engine loom. The biggest problem i can see at the moment is the number of wires in the under dash plug on the r33 loom compared to the r32 loom. The wiring for the Wipers can simply be removed from the r32 loom and pluged back in so the whole wiper amplifier setup and wiring can be removed completely from the r33 loom.

I am currently trying to figure out where each of the wires in the big plug at the front of the engine bay go on the r33 loom, i know one is the ac relay trigger, one goes to the aac valve (i think) and one is running to the under dash plug (dunno what it is though). Most of the rest of the wiring is fairly easily traced back to the ecu or sensor plugs.

Then it's a case of doing the same on the r32 engine loom and joining the appropriate wiring. Not exactly rocket science but time consuming when your working off bits and pieces of wiring diagrams scattered around the internet and some of the plugs aren't shown (like why does an r33 have 2 plugs going the the aac valve when the r32 has 1 and why dont my diagrams show this or the egr valve?).