NEO vs Normal

[machg]

I have read that the RB DE NEO motors perform signifigantly better than the earlier Non NEO motors. Is this true? If it is, is it because the NEO motors run variable valve timing? Why do VVT engines seem to make more power AND use less fuel than earlier engines? It can't just be cam timing, surely!? Are the gains worth the extra complexity and cost of buying a NEO? All opinions appreciated, (especially if you are a mechanic!)

machg

[Eug]

i have heard that these engines (25det) are capable of producing around 200kw stock.

they have stronger internals and little extra bits here and there - though

i am not sure about what extra bits exactly.

obviously these engines have a far greater potential than the standard rb25de

and rb25det.

maybe someone can clarify this alot more than me.

i am not sure if the extra complexity is worth it - all depends on how much dosh

you are willing to fork out.

[Ant]

The NEO RB25DET's are good for 206kw. The RB25DE (NA) NEO makes the same amount of power as the non-NEO engine but at a lower RPM (6000 vs 6400) and the torque is higher (250 vs 230NM).

Basically VVT allows the valve timing to be optimised across the RPM range, rather than being the compromise that fixed timing cams allow. See here for a full description of how it works:

http://www.geocities.com/gkurka2001/CarTech/vvt_1.htm

As for whether or not it is worth it - depends on whether or not the tuning shop you use is familiar with VVT engines. VVT has a lot to offer in terms of (usable) power gains, but as it is a relatively new technology and is dependent on electronic control tuning it for more power is far more complex than a non-VVT engine.

[TODA AU]

As Ant said, the NVCS system combined with high lift, tight lash cams offers superior performance.

The main difference between the two 25 engines is within the cylinder head.

That is, the valve train & cams... (The cam control is basically the same as other RB25’s)

While the early RB25 uses hydraulic lash adjusters. The RB25NEO engine uses solid lifters.

Where the early RB25DET uses 240deg @ 7.80mm cams for intake & exhaust.

The RB25NEO uses 236deg intake & 232deg exhaust cams @ 8.40mm lift.

It’s the greater lift combined with the shorter duration that necessitates the need for solid lifters.

Further, the RB25NEO is a better starting point as an engine to modify because of the solid lifter head.

This offers a much wider selection of camshafts.

From Tomei 260deg @ 9.15mm Pon Cams to those intended as drop in's for GTR's.

Max lift for drop in cams for the NEO is 9.15

Thus 9.1mm ~ 9.15mm aftermarket GTR cams can be used without a change of valve spring.

An example of this would be a 272deg @ 9.1mm TODA GTR camshaft.

NB: NVCS system cannot be used with GTR camshafts in RB25NEO engine.

Though once the cams are larger enough, the NVCS becomes irrelevant anyway.

(Aftermarket engine management essential)

By comparison, the early RB25 can only cop 8.50mm lift before you need to change the valve springs. This limits your drop in cam selection to Tomei Pon Cams or modified std GTR camshafts.

The rest of the core of engine is basically the same.

9.0:1 C/R / 86 x 71.7 Bore & stroke / same block / same head / etc

Engine electricals are different. Crank angle sensor / coils / ECU etc

IMO, the original RB25DET in reality is a bit of an old nail these days; the NEO version brings forward & a little more inline with the dynamics of more modern engines.

Through the use of higher lift, tight lash (less duration) cams & the rather simplistic NVCS (variable cam) system, allow the NEO RB25 to pass the more stringent, modern emission tests & still deliver acceptable power & fuel economy.

Hope that helps.

Cheers

Adrian

[666DAN]

Excellent reply!

[rainster]

i have had both types of motors,and i feel that the neo motor is a very revvy motor but at low revs very mellow,when you hit about 2800 revs you feel like you hit powerband like a twostroke motor bike where as torque range on a earlier desighn is pretty much same torque curve all the way through as i found when compareing dyno print outs of both types of engines.also the neo has aprox. 10% more kw then earlier desighn from factory it is the heads,cams,and engine management that make it more powerful and fuel efficient the engine blocks,piston are the same a few small changes but not much mainly in the crank.