Rb25-30de Into Hr31

[GTS_Retro]

Just a quick intro on my ride http://www.skylinesaustralia.com/forums/Hr31-Gts-t228525.html

I have been reading thru this section and partly thru the (167pages of the r33 rb25-30) thread for a few weeks, I have been inspired to do something different with my car.

At home in the garage I have a R33 S2 RB25DET and a R31 S3 Rb30E

I want to build a 25-30 NA, to plonk into the HR31.

I need some recommendations on building a high compression NA hybrid.

What I plan for the block so far, full strip down clean etc. hone, new big end bearings main bearings, if in good condition re use rods, new bolts etc. but unsure weather to use rb30 pistons, balance crank.

Basically give the block a freshen up.

Need some advise on combination of OEM pistons to use with head gasket to get a high CR (9:1 or close?) for throttle response, head shaved etc.

There seems to be so much wealth of knowledge and experience here any help or tips is much appreciated.

[Craved]

9:1 seems pretty low for an NA motor.

i'd go rb26 TB's and trumpets think it might be Blitz that sell the conversion plates - not 100% but can be had

what cam duration and lift you thinking of going?

[GTS_Retro]

What would a more realistic CR for a NA be?

I was thinking of leaving the VVL head functional.

I reasearched the 26 ITB set up it would be definatly the top choice, however i would like to get the engine together then look at more development in the future. for now sticking with a custom plenum and single TB.

[TiTAN]

~11:1 maybe a little higher if its good fuel.

[GTS_Retro]

Gonna run standard R33 ECU and on 98RON petrol.

Im using;

RB25DET head, RB30e Block, RB30e Pistons.

This should give an approx CR of 8.3-1

Just not sure on head gasket, will prob use a RB30

I will have the block shaved to Xmm to increase CR.

My question is how many Xmm to shave to increase CR to a good level for NA. taking into account pump fuel and standard ECU?

Edited July 22, 2008 by GTS_Retro

[Adriano]

Not trying to knock what you are doing, but just remember that it is unlikely you will make more than 160rwkw, which is easily achievable with any of the turbo ortions. I would take this into account when building it, and allow for the fact that you may want to turbo it in the future.

[fletch rb30]

You can just stick in r33 rb25de pistons to get good comp, i think 11:1. should do the trick

[infamous_t]

This is just my opinion, but NA RBs are a waste of time... Look at a VH41DE instead for Nissan NA power

But if you insist on the NA RB30, I believe someone in the NA section has a build underway

[R31Nismoid]

Id be more questioning the reasoning of the stock ECU

Its going to be the highly limiting factor for most of it.

[infamous_t]

Id be more questioning the reasoning of the stock ECU

Its going to be the highly limiting factor for most of it.

Would be worthwhile if retuned/chipped... but still a bit of a PITA to deal with

[GTS_Retro]

Well my initial plan was to go turbo i have the 25mani and turbo. but i just wanted the simplicity of NA. I thought 160kw more guts from down low and throttle responce would still make some fun in the 31.

Im still open to beeing talked into turbo..

So what ecu would people reccomend to use as i have just read that the 33 can not be retuned,, is that correct?

[James_03]

power-fc, otherwise late model SAFC with the oem ecu, all depends on how simple you keep it.

my first motor was one of these in an aus spec 31, mid range is great. Used rb25de non turbo pistons and ran off the OEM ecu entirely. It was a fairly basic setup but just hi comp with hacked up rb30 extractors to suit the 25 head.

[GTS_Retro]

power-fc, otherwise late model SAFC with the oem ecu, all depends on how simple you keep it.

my first motor was one of these in an aus spec 31, mid range is great. Used rb25de non turbo pistons and ran off the OEM ecu entirely. It was a fairly basic setup but just hi comp with hacked up rb30 extractors to suit the 25 head.

Any idea on what kw it made?

[James_03]

Never went on the dyno mate so couldn't tell you sorry. Just had afr's checked with a wideband and away it went.