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Help With Rb25det Neo

Adam J.

By Adam J.,
in Engines & Forced Induction

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Adam J. Rookie

Adam J.

Posted
Posted (edited)

First off, I may have put this in the wrong section so feel free to move it. So I am think ing or swapping out my rb20det in my 1991 gts-t and swapping in a rb25det Neo engine, and I just had a few questions that I wanted to clear up before going any further. So thank you very much and I hope to hear from anyone that has any knowledge on the engine.

What is the normal cost of a Neo engine without the tranny?

What should the compression be?

What are common problems with the engine?

Will the Rb20 transmission work with the Neo, if so up to what horsepower?

Any clutch recommendations?

How is the swap? (time/skill)

How is it to wire up?

Will an rb20det PowerFC (AP version) work with the neo? Or should I sell it and buy a rb25 one?

Basically anything that comes to mind about the RB25 Neo

What should the price of this RB20det be?

No transmission

Comp test showed 150 across

Knock reading never over 16

Complete with smic, maf, pod filter, hks actuator set to run 12lbs, stock fuel pump, screamer pipe, mines ecu, and stock clutch (good condition)

you can pm me, reply, or email me at [email protected]

Thanks again for reading this

Edited by Adam J.
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Marco-R34GTT Grand Master

Marco-R34GTT

Posted
Posted

I haven't done a swap myself, I know nothing about it.. However I'm driving an R34 GTT and it has the RB25DETT NEO engine... All I'm gonna say is that you've made a good choice... They definitely move along... Nice smooth and grunty engine...

blind_elk Grand Master

blind_elk

Posted
Posted

My experience is with a Stagea RB25DET into a R32 GTS4.

The engine drops straight in. The gearbox bolts straight up, and is handling 180kw out through all 4 wheels (estimated 240 at the flywheel). You need to retain your (RB20) P/S pump (for the HICAS).

The NEO is probably similar to the Stagea, in that it has VVT. So, a RB20 PFC will not run it (doesn't know about VVT); best getting a PFC to suit the engine. Get the setup as a half-cut so you get the loom as well to use with your new PFC (you can possibly off-load the gearbox, brakes, etc to recoup some of your cost). A half cut will also give you an ECU, so no need to get the new PFC immediately. No idea on cost; probably 3-4k. Fit at least a HD clutch pressure plate; ceramic clutch and a lightweight flywheel are optional.

It's probably a day each to remove your engine and install the NEO. You will need an engine crane (hireable). There is a lot of "remove <something> to gain access to <some bolt>", so it's fiddly, time-consuming work.

Wiring in - step 1: remove front bar and LH guard. (I'm not kidding!)

As for your current engine, probably not really worth much at all. They are dime-a-dozen from wreckers. You might get 1k if you were really lucky.

Hope that gives you some idea of what's involved. It's certainly worthwhile - the RB25 has torque to burn!

Adam J. Rookie

Adam J.

Posted
  • Author
Posted

hey thanks for all your replies guys, and ya I hope i can find a buyer for my AP PFC and am able to find an rb25 version. As for turbo i will be running an hks 2535, with some 550cc injectors, and all the other needed supporting mods. thinking of replacing cams as well.

BAMR33 Mentor

BAMR33

Posted
Posted

The problem you'll face will be the expense. Neo engines aren't cheap and don't make that much more power than the earlier rb25's. If you're asking questions like 'how to wire it up' etc. I think you'll run into big troubles carrying out this conversion.

You should consider working the rb20det, by the time you add all the costs together for the conversion you could have an rb20 with a reliable 240rwkW+ and still have money money left over to reco the gearbox if needed.

blind_elk Grand Master

blind_elk

Posted
Posted

If you get a half-cut, then all you should have to do is swap the loom and ECU over. I treated myself to a new ECU (Wolf 3D 4+), which I had to wire in - that took me a couple of days sorting out which wires I needed to keep, and which wires I could discard.

As they say in the classics ... "CUBIC INCHES COUNT". The RB25DET conversion is well worthwhile. My GTS4 went from 115 at all 4 to 180 at all 4. I doubt you could get that result for the same $$ rebuilding a RB20.

  • 2 weeks later...
Adam J. Rookie

Adam J.

Posted
  • Author
Posted

So should the compression be around 155-165? i have a guy telling me that his is 140-145 across and saying that's good, but im pretty sure it isnt.

About the PFC, it is extremely hard to come by any kind of PFC being that I live in canada so does anyone think it would be a good idea to sell it on here and then ship it and then buy an rb25 PFC on here and ship it back?

As far as the rb20 bein worth nothing.... up here they seem to be worth a bit. since they arent everywhere i guess

thanks again

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