Rb25det Vs. Neo - Why The Power Difference?

[Peter]

Hi Everyone,

Not sure if this has been covered before, but it has been on my mind recently, so I thought that I would draw from the wisdom of SAU....

From what I understand, when comparing the RB25DET (R33) and NEO (R34), the NEO engine makes 206kw (stock), compared to RB25’s184kw (stock) - why / how does the R34 make more power?

From what I understand the R34 has a bigger SMIC, different turbo, different engine management - not sure about injectors etc.

But if you were to get an RB25DET and a NEO side-by-side and say stick the following on both engines:

Apexi PFC

Pod Filter

FMIC

Turbo

Fuel Pump

Bigger fuel injectors

and then tune them the same, would they then both then make around the same power - (bringing the RB25DET upto the NEO level) or are their more internal mechanical differences that I am not aware of?

Look forward to your responses!

Thanks,

Peter

Edited March 10, 2009 by Peter

[TiTAN]

Mechanically they are very different engines.

[lachlanw]

adding those mods to them will multiply the difference between them . its differences like nvcs is continusly variable as opposed to on/off. begger exhaust valves . solid lifters/diff cams . and 5 years further electronic development

[gotRICE?]

Isnt there a bit more compression in the NEO too?

Its pretty clear, if you start with more power stock, and add parts you will surely end up with more power.

[lachlanw]

and you couldnt "tune them the same" . eg neo would make more power/torque on same boost or same power/torque on less boost .

[R31Nismoid]

Overall even with the parts - the limit factor is boost/airflow.

The GT-t turbo is marginaly bigger than the GTS-t turbo, so you get ~10-15rwkw more... but thats it if you do 'every' basic mod short of changing the turbo itself.

Equally sized turbos (upgraded) i would expect very little difference overall. Happy to be proven wrong but i dont think the gains would be anything major over either motor once you start talking boost

[FineLine]

add to that the fact that the 34 weighs a fair bit more than the 33 and the neo has proven to be a bit of a bear to modify and again, there wouldnt be much difference between the 2.

[T04GTR]

higher lift cams and diferant cam timing. better intercooler and bigger turbo and higher comp ratio

[Lithium]

From what I've seen the majority of it is the extra boost they run, and of course the supporting mods to allow it to do so safely (bigger turbine a/r, intercooler...).

Whenever we dyno'd them with intake, exhaust, fmic and say 10-11psi they always seemed to make similar power. The only R34 I know of which has dynod on the same dyno as my car was tuned on with upgraded turbo etc was only running a T3/T4 and made a fair bit less power.

[sneakey pete]

  gotRICE? said:

Isnt there a bit more compression in the NEO too?

Its pretty clear, if you start with more power stock, and add parts you will surely end up with more power.

Yes, but if when adding more parts your replacing what it was that made the NEO more powerful in the first place, then you wouldn't get the difference. Guess it depends on turbos.

[Al]

We are talking about RB25 Vs RB25neo, not r33 Vs R34.

So keeping that in mind we are comparing the performance of the engines not the cars.

  T04GTR said:

higher lift cams and diferant cam timing. better intercooler and bigger turbo and higher comp ratio

  lachlanw said:

adding those mods to them will multiply the difference between them . its differences like nvcs is continusly variable as opposed to on/off. bigger exhaust valves . solid lifters/diff cams . and 5 years further electronic development

So do people really think all the above enhancements don't improve the performance?

I had a high flow rb25 turbo (with the VG30 ext housing) and my r33 rb25, with tomei poncams and extensive race head porting, managed to produce a respectable 268rwkw. When i upgraded to the GTRS turbo, i sold the high flow to a mate with an r34. The 100% stock/unopened neo engine made 273rwkw using the same turbo on the same dyno.

In other words; i had to spend over $2k to achieve the same results as a std rb25neo.

[Lithium]

  Al said:

I had a high flow rb25 turbo (with the VG30 ext housing) and my r33 rb25, with tomei poncams and extensive race head porting, managed to produce a respectable 268rwkw. When i upgraded to the GTRS turbo, i sold the high flow to a mate with an r34. The 100% stock/unopened neo engine made 273rwkw using the same turbo on the same dyno.

In other words; i had to spend over $2k to achieve the same results as a std rb25neo.

Did you get any before and after cams and race porting dyno plots?

[bozodos]

The NEO also seems to be quite a bit more economical than the RB25.

[T04GTR]

perhaps the wrong type of porting was to blame.. bigger is not always better.

[R31Nismoid]

  Al said:

So do people really think all the above enhancements don't improve the performance?

I had a high flow rb25 turbo (with the VG30 ext housing) and my r33 rb25, with tomei poncams and extensive race head porting, managed to produce a respectable 268rwkw. When i upgraded to the GTRS turbo, i sold the high flow to a mate with an r34. The 100% stock/unopened neo engine made 273rwkw using the same turbo on the same dyno.

In other words; i had to spend over $2k to achieve the same results as a std rb25neo.

They might, but very minor at best.

The cams is nothing major, the timing is overidden by aftermarket ECU's, and a comp ratio increase (again minor) isnt going to instantly give you massive gains. Depending on circumstance/boost it might even hold you back.

Its all done in the form for a stock motor, to meet emissions. Once you really start playing most of it goes out the window when (probably) 1psi negates all those changes.

As Lith said - did you get a before/after the porting? If you didn't, very hard to tell to the point of really showing not a lot.

When you think i made 270rwkw stock head, then over 370rwkw on 104 fuel (and could have made more) again with a stock head (Non-neo)... Guilt-Toy has made 370rwkw Non-NEO head also with response to make you drool...

I don't think your one isolated example is that accurate in this instance and there is much more at play there to be able to simply say you spent 2k and couldn't beat a NEO.

I've seen no result here to date that says NEO RB25 heads give leaps and bounds gains like you are talking.

Could be all your porting was putting the turbo out of efficiency, and so the list could go on

[joeyjoejoejuniorshabadoo]

  R31Nismoid said:

Overall even with the parts - the limit factor is boost/airflow.

The GT-t turbo is marginaly bigger than the GTS-t turbo, so you get ~10-15rwkw more... but thats it if you do 'every' basic mod short of changing the turbo itself.

Equally sized turbos (upgraded) i would expect very little difference overall. Happy to be proven wrong but i dont think the gains would be anything major over either motor once you start talking boost

to throw in another viewpoint......

IMHO you are exactly right ash...

bombtrack and i both have unopened 25's with HKS 2835 pro s turbo's, only mine is a 33 and his a 34

with stock turbo's chris's was a tiny bit more responsive than mine, and made 5odd rwkw more top end

now with the same setup (pretty much) they have leveled out.

on pulp i have 270rwkw running 18psi and he has 275rwkw running 18psi...

the only difference is cams... mine are stock, his tomei drop in items...

same tuner, same dyno, no major weather differences on the tuning days.

i get better transient response, but not heaps, <500rpm and he gets 5rwkw top end.

[SDEWY5]

this is interesting..

[bozodos]

Agreed, I was always under the impression that having the same block to the GT-R (just on strength alone), the solid lifters, and continous VCT as well as the better flowing heads stock made the NEO a far superior motor.

[Bass Junky]

Contrary to populart belief, Neo NVCS is also just on and off. NOT continuously variable. It just turns it on and off more than once through the rev range.

Neo has superior heads, slightly larger turbine for higher flow, different stock cams.

Also has different rods and crank but neither of these are performance adders, just reliability. Maybe lighter weight for better revving.

Neo also has an engine cover. It looks better.

[joeyjoejoejuniorshabadoo]

nu-ah... the engine cover looks teh ghey....

there have been studies done... facts found... scientists, test tubes, lab coats, bunsen burners, calculators etc