Neo Rb25 Vs R34 Rb26

[zebra]

Only if you can get enough timing into the thing.

also Rb26's have larger valves, different chamber shapes etc.

All those things will affect the curve/peak power

[Rolls]

I was told the neo's had larger valves and a smaller combustion chamber, much like that of the 26.

[zebra]

the chamber is definatly different, I always thought the NEO had the same valve sizes as the earlier 25's, I could be wrong though.

[Rolls]

I guess we really need a workshop manual to see what the exact differences are, that would surely have things like that in it.

[zebra]

I do remember quite a few people saying the neo heads won't take a lot of timing advance before det, despite running the same comp as the earlier ones, something about the chamber shape.

[Rolls]

smaller combustion chamber and 26 rods to make up the compression, guess I will find out soon.

[zebra]

This is apparently a NEO chamber

and this a 26

Photo's are not verified as 100% accurate

but look very similar to me

[zebra]

And also similar to the Cosworth BDG setup

[dori34]

The RB25NEO does have a smaller CC compared to earlier RB25s

RB25 combustion chamber = 63cc

RB25 Neo combustion chamber = 51.5cc

[raZ1911]

Doesnt the S1/2 RB25s have the VCT on 1 side when the Neos have it on both intake and exh?

[bigmikespec]

Intake only. Variable on the exhaust is really just for emissions not more power.

[bigmikespec]

Why don't you try this: http://www.gtr.co.uk/forum/152585-switcheroo-rb25-head-wears-26-hat.html

Seems like Mr Red R still has some things in his big back of RB tricks!

[DVS JEZ]

Why don't you try this: http://www.gtr.co.uk/forum/152585-switcheroo-rb25-head-wears-26-hat.html

Seems like Mr Red R still has some things in his big back of RB tricks!

RRR sure does

[R31Nismoid]

Nothing that most other places haven't already done

[bigmikespec]

If you are reffering to the Racepace VCT effort I have been told is was a NEO head. In which case what Red R is doing is certainly different to that.

[R31Nismoid]

Not everyone posts up what they get upto, you should know that.

[pipster11]

pretty sure the neo vct is constantly variable whereas s1/s2 r33 was on/off

because to set the timing you have to use the consult to stop everything shifting about

[Simon-S14]

thats got nothing to do with the VCT, thats the CAS and ecu varying the timing.

the VCT is on/off. and its internally the same as a 33 item.

[discopotato03]

The storey I get is that all turbo RB25s and 26's have the same size and shape chambers and valve head diameters as well . A look around in aftermarket valve circles will tell the storey here if not in factory WSMs .

You could also look around for std reeplacement R33 and R34 RB25 pistons to see if the crown height/style/dish volume is the same .

I tend to think the six throttles and twinned turbos give a std RB26 lower restriction gas paths at high revs .

People should think of compression as dynamic rather than static and I think in many cases the 26's would be higher dynamic once the throttles opened up more than a tad .

I think the main difference between std 26s and Neo 25s is that the Neo would make better part throttle torque because its not intended to be a power at revs engine like 26s were intended to be .

I think valve train wise hydraulic cam followers , buckets if you like , are going to be significantly heavier than plain buckets , "solids" , so less valve train innertia for the valve springs to have to control .

Hydraulic buckets are all about no maintenance because they self adjust enough under normal operating conditions .

It is a major and expensive PITA to have to reset clearences on an under bucket shim engine like an RB26 or FJ20 .

Belt off pulleys and cams out to remove the buckets so you can get at the shims .

It always made me wonder why people ran single throttle and single turbo RB26s particularly if it was in a RWD car , if they changed pistons rods and cams then about the only minor differences are the stroke and slight port differences . Some might argue that a 26 block is a bit stiffer but how many people break blocks in a RWD car ?

The jury is still out about twin scroll single and parallel twin turbos so IMO probably the best thing 26s had was the six throttle inlet system and possibly the water riser/log system .

If you can live without these then a Neo should be cheaper to buy and still have the non hydraulic bucket valve train .

A .

[DR 32R]

So how do the AWD block RB25s neo and non neo differ from the RB26? Many of the Stagea blocks I've seen have interchangeable sump and sump parts with the Rb26.

Edited June 15, 2011 by WHITE gtt