Neo Rb25 Vs R34 Rb26

[Rolls]

How do these motors compare? The neo has a very similar head, rods, pistons etc but 100c less displacement, however the neo has VCT as well.

For a street car would the VCT not be more beneficial than the extra displacement? Or are there other items the RB26 features which makes it a better engine.

[R31Nismoid]

I don't even think it's 100cc, more like ~65-70

Either way not noticeable, for the street - VCT. Hence you see a few NEO/26's getting around now.

25 NEO heads on built 26 bottom ends. Its to get the VCT, kinda like poor mans V-CAM. Much cheaper but less options which for the cost isn't too bad.

Depends overall what you want of course, if you are talking stock motors I'd get a NEO for a conversion personally if budget is a consideration. You'll get a pretty good setup and only have to change on turbo - bolt on etc.

[GTScotT]

+1 to above.

I certainly don't see any magic in the RB26. A good single turbo on the NEO with the aid of VCT will make for a good setup.

[Rolls]

Yeah I've just bought a neo to replace my old non neo 25, was just curious how close it was to a 26. I've heard the VCT is better than that on the S1/2 VCT, do you know what the actual differences are?

Cheers.

[DVS JEZ]

RB26 with variable cam timing RRR

[Rolls]

RB26 with variable cam timing RRR

Sounds like that is basically what the neo is lol, 50cc of capacity is nothing.

edit: The earlier rb26s had 8.5:1 compression, do the R34 rb26s also have 8:5 ? cause the neo has 9:1

edit2: apparently they do, imo that makes the neo quite a bit better than the 26

Edited June 12, 2011 by Rolls

[rondofj]

Im loving my neo more than myself, all in all a great motor no doubt, its only mildly modded though, but then again i still want a RB26!! Dont know why, i guess every RB25 owner does... Dont think theres much differences in them

[Simon-S14]

neo's are fantastic engines... the only thing they dont have over an RB26 is the high RPM limit and ITB's. I bought some RB26 ITB's and plenumn set up for mine but the thing is the factory long runners is what gives it so much midrange torque. putting short runners on there will move that torque further up in the power band. So i'll be looking at adapting the 26 set up and then making a custom plenumn with longer runners.

[Rolls]

See I never got why rb26s get a higher rpm limit, in Bathurst they limited them to 7k not 9k which certainly says something to me. Also this might be wrong but I see a lot more blown up rb26s than I do rb25s, could this be due to the higher rpm limit? What allows them to safely rev higher, is it really any safer than revving say a 25 that high?

[zebra]

See I never got why rb26s get a higher rpm limit, in Bathurst they limited them to 7k not 9k which certainly says something to me. Also this might be wrong but I see a lot more blown up rb26s than I do rb25s, could this be due to the higher rpm limit? What allows them to safely rev higher, is it really any safer than revving say a 25 that high?

Solid Lifters in the RB26 over the earlier RBs, but NEO's have solids too.

Cant see why the 26s rev higher...Longer stroke, same journal sizes mean the 26 will be "maginally" harder on bearings over the 25

[FordyR31]

I don't know how true it is but I heard.......... lol...... The earlier 25's, the VCT was more for off boost driving and worked up to 3000rpm and in the 34 NEO 25 the VCT works over the whole rev range... Can anyone else confirm that as I would like to know myself if that is correct or not.

[zebra]

No, same as the RB25, just on at 1100-1200 rpm and off at 4700

[DVS JEZ]

5400 for neo

[zebra]

ah, so thats the difference then

[Rolls]

I've heard internally the VCT works different on a NEO, but externally it is the same (an on off solenoid), I have no idea what the internal difference is though. But yeah, surely there is no reason why the rb26 gets a higher rev limit, surely this is why they blow up so often with people setting redlines at 9k? If someone said they were revving their 20 or 25 to 9k everyone would think they are loopy.

edit: apparently the rev limit is 8200rpm on the 26, it is 7200 I am fairly sure on the 25.

Edited June 13, 2011 by Rolls

[rondofj]

What does vct stand for- variable something timing? And if thats something good then how come the 26 which is the ultimate nissan engine (we will keave out the vr38dett for now) dosent have that? Also how will a vg30dett from a 90s 300zx compare to the 25 neo and 26- ive heard they r stronger and with a bit more punch due to the 3000cc but we all know zeds r a b$$tch to work on, maybe thats the reason the 300zx hasnt taken the import scene like the skyline

[zebra]

VCT = Variable Cam Timing

As for no VCT on the 26....well its just another thing to go wrong/fail in a race environment.....F1 cars dont run VCT so why would Nissans Production racer?

[Rolls]

the vg30det is a massive motor which doesn't really fit in anyone's engine bay and is a pig to work on, also most of them have overheating issues in the 300zx due to inadequate cooling so they have earned a bad reputation.

VCT stands for variable cam timing, I really have no idea why they don't put it in the 26, I can't imagine it really adds much to fail and it adds midrange to the car which is always useful.

But yeah with the VCT and higher comp, if you had the same turbo surely the neo 25 would make a bit more power than the 26?

Edited June 13, 2011 by Rolls

[N1GTR]

But yeah with the VCT and higher comp, if you had the same turbo surely the neo 25 would make a bit more power than the 26?

Its not that simple, having the same turbo means you should get the same result in terms of power on each (if all other factors are the same) however the VCT has the potential to give more area under the curve by altering the cam before the turbo gets into its efficiency.

[Rolls]

If you are flowing the same air (same turbo and equivalent boost levels) shouldn't the higher compression give you more torque hence power? Higher compression ratio = higher percentage of energy extracted.

Edited June 13, 2011 by Rolls