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Rb20 To Rb25 Conversion In R32 - Which Parts Can I Retain From My Rb20!?

Lukaz

By Lukaz,
in Engines & Forced Induction

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Lukaz Community Regular

Lukaz

Posted
Posted

Hey all, doin a 25 conversion on the R32. Im just wodering what parts from my Rb20 will swap over? I only have Rb25 block and head, no manifolds, CAS, etc etc.

Im 99% sure my exhaust manifold will swap over fine. But what else will? and What will I need to buy seperate?

Cheers in advance!

bubba Grand Master

bubba

Posted
Posted

Exhaust manifold will be fine, but I don't think the inlet manifold will be.

I think the CAS's are the same but fuel rail/injectors are not. That being said, if you manage to get the inlet manifold to fit you could use the RB20 rail/injectors aslong as you're using the RB20 ecu. As for other sensors etc, I've got no idea.

Sorry I can't be much help, I recently did an RB30 swap into my R32 but we used a 25DE head out of an R32 so everything was pretty much a direct swap off the RB20.

Lukaz Community Regular

Lukaz

Posted
  • Author
Posted

Cheers for the reply mate

I was hoping inlet manifold would fit, should be pretty easy to find atleast. Im gonna be running a custom fuel rail for the injectors as I have GTR ones already and can't be bothered buying new ones, its only around $270 im told so thats ok. Im running a wolf so luckily that should be easy swap, just need to rewires the loom abit I think?

What are the R32 DE heads like in comparison to R33 RB25det head??

bubba Grand Master

bubba

Posted
Posted

No VCT and practically identical to an RB20 head but with larger ports. This particular head flowed enough to make 460rwhp on the last RB30.

As for the intake manifold, the reason I got this head is my mate wanted to get a Greddy plenum but they only bolt to DET heads AFAIK.

I used the 25DE intake manifold as opposed to the 20 item as the ports matched better.

If you have a search for the ecu remap thread there are some attachments containing pinouts for the different RB engines which will probably be of some help :P

zertek Proficient

zertek

Posted
Posted

hey mate, just gone through this myself.

The exhaust side is the same between the 20 and the 25 so you can obtain your manifold. Inlet side is smaller on the rb20 though. So you will need to find yourself an intake manifold for the 25. You'll also need injectors as per the top feed and side feed difference. heater hoses are different size so you will need to fit reducers on the 25 hoses so they can connect to the previous 20 hoses running along your fire wall, obviously your loom is different although you can hold on to the rb20 ecu and give it a retune. you may also want to consider changing to an rb25 gear box, from what i have read the 20 gear boxes dont stand much of a chance up against an rb25det. your Crank angle sensor (CAS) is also the same if you dont already have one on the rb25. Your alternator, power steering pump, air conditioning can all go on the 25 as the brackets are the same. Thats about all i can think off from the top of my head at the moment.

Hope this helps mate :P

Cheers

zertek Proficient

zertek

Posted
Posted
Cheers for the reply mate

I was hoping inlet manifold would fit, should be pretty easy to find atleast. Im gonna be running a custom fuel rail for the injectors as I have GTR ones already and can't be bothered buying new ones, its only around $270 im told so thats ok. Im running a wolf so luckily that should be easy swap, just need to rewires the loom abit I think?

What are the R32 DE heads like in comparison to R33 RB25det head??

Is your wolf a wire in or plug in? if its wire in, your better off doing what i am doing and leaving the loom in place and changing over the neccisary plugs to 25 ones. It's not expensive to have this done at a workshop. Im quoted 550 to modify my loom and tune up. These are the only 2 things that i will not be doing myself on my project. the wiring is better off left to a pro because the injectors need to be wired either in series or parallel depending on thier impendance and ohm reading. On the other hand if your wolf is a plug and play, just put the 25 loom in and your away.

The 32 DE heads im 90% sure have smaller cams than the rb25det head.

zertek Proficient

zertek

Posted
Posted

oh and if your still in need of a inlet manifold for a 25 i have one. I went with a front feed plenum in the end. PM me if your interested. I also have various other RB25 bits and peices that i am not using if you need anything. cheers

Lukaz Community Regular

Lukaz

Posted
  • Author
Posted

Excellent help guys thanks again!

Got a price on a fully assembled rb25det head - does $450 sound like a good price?

My heads rooted and just sussing out my options, mechanic rekons might get away with re-doin the head for around $700 hopefully.

Also, yes im pretty sure I will be in the market for a 25 intake plenum so I will probably PM you next week sometimes hopefully, Im not goin ahead with anything untill the block is totally stripped down.

GTS4WD Grand Master

GTS4WD

Posted
Posted (edited)

Did an Rb25DEt VVL and the rb20det fuel pump is not enough.

The inlet mani IS NOT appropriate..

The front pipe of the exhaust is different.. I.e it has different flanges and will not mate appropriately..

And be warey.. please tell me if after the conversion you have difficulties with the engine starting hard.. I found that the first week or so it was sweet as, and got harder and harder.. to the point it has to crank over 6 or so times to start..

other wise everything else you have seems to be in good order

Edited by GTS4WD
Lukaz Community Regular

Lukaz

Posted
  • Author
Posted

I already have aftermarket injectors, fuel pump, computer, coilpacks, front dump pipe.

Only thing ive been told out of those mods that won't fit directly is injectors but ive been told theres an aftermarket fuel rail i can buy that will sort that out.

Wolf is plug'n'play type, mechanic rekons shouldn't be a problem rewiring that to suit up plus my coilpacks.

zertek Proficient

zertek

Posted
Posted

hope its not the starter motor behind this.... mine isnt finished yet and i will be using the rb20 starter motor on the 25 still. Hope i dont have to change that too :D

Did an Rb25DEt VVL and the rb20det fuel pump is not enough.

The inlet mani IS NOT appropriate..

The front pipe of the exhaust is different.. I.e it has different flanges and will not mate appropriately..

And be warey.. please tell me if after the conversion you have difficulties with the engine starting hard.. I found that the first week or so it was sweet as, and got harder and harder.. to the point it has to crank over 6 or so times to start..

other wise everything else you have seems to be in good order

Lukaz Community Regular

Lukaz

Posted
  • Author
Posted
what wolf version is it??? hopefully its map sensored. if not then you'll need to find yourself an AFM.

V4 bro, yeah its map sensor. So glad majority of the parts swap over without much hassle.

bubba Grand Master

bubba

Posted
Posted

Pfft, I used the RB20 starter on my RB30, no problems :)

As for the 25DE cams, they're just NA cams, I can feel them do their stuff at 4000rpm. I would say the RB20/25 cams are optimised for the extra breathing across most of the rev range due to the early spool of factory turbos.

The powerband of the NA cams should suit the GT30 I eventually get, but for now, with no lag and full boost so early, it gives you an extra little kick halfway thru the rev range.

1400r Veteran

1400r

Posted
Posted (edited)

25det and 20det starter motors are different size

front and dump is exactly the same I reused my rb20 one

also of note is the front pipe is the same as s14,s13,s15,a31,c33,c34,stagea etc etc

Edited by 1400r
abu Grand Master

abu

Posted
Posted (edited)
what wolf version is it??? hopefully its map sensored. if not then you'll need to find yourself an AFM.

All the WOLF's run inbuilt MAP sensor :)

also of note is the front pipe is the same as s14,s13,s15,a31,c33,c34,stagea etc etc

Thats awesome, I never knew that!

Edited by abu
bubba Grand Master

bubba

Posted
Posted

^^ That's not what the clutch guy that built my last clutch said.

If what you're saying is the case, will that mean I need a new starter motor when I upgrade to a 25 box?

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