Free Revving

[zanda]

I picked up the latest edition of speed, in which they alude to the fact that the Top Secret neo GTRs are running 12000rpm redline. I havent got it with me, but the essential gist was that this should be acheiveble on any finely tuned rb26.

I take a fair bit of what I read in speed with a grain of salt, but this leads me to thinking...

what rev limiters are some of perth/WA's better/more developed nissan engines running? what, apart from a fairly short stroke, does it take to run really high RPM?

[MattyB]

from what i know the headwork is a very important part of doing this. have springs etc that can react that fast. im sure steve could add more on this subject thou.

[Denver]

A very very balanced crank, strengthened and all that sort of gear, i doubt theyd be a stock crank, they tend to twist and flex a lot with high RPM..

[GTS-t VSPEC]

What's the point of the 12000 rpm? Even for the top speed GTR's there isn't any benefit of past 11000rpm, and most will fall off power well before this. So apart from highspeed runs can't see why you'd bother.

[zanda]

Paul, why is that?

I can understand how the benefits/efficiency could reduce, but I'm wondering what is the limiting factor if the turbo is sized so that it doesnt run out of puff?

[GTS-t VSPEC]

I think limiting factor become stuff like head flow and cam sizing. I know the cars (Jap Import) that they setup for highspeed runs make peak power at about 9000rpm, but they push them out further to make use of the gearing. In other cars like F1 etc they have much higher rev limits due to different head design.

[Denver]

on a silly side note, the HKS gt-r spins to 11,000 and gtr-700 spins to a couple more from memory, but we're talking 1500hp cars here with a pair of 3037's..

so they have the turbo's to make use of the extra RPM..

there also very highly developed motors..

[tomj]

I suspect they want as wide a powerband as possible,

even if power falls off slightly it isnt as dramatic as shifting up at say 9k and falling into a torque hole.

[zanda]

so can anyone advise the higher rpms used in Perth's nissans?

[fane]

http://www.automotiveforums.com/t145119.html

[GTS-t VSPEC]

Al, Without a billet crank you wouldn't push past 9,500 on a GTR, and 10,500 with billet crank and flash harmonic balancer with engine fully balanced.

[GTS500]

interesting all rb26's i know of in perth are running between 8500 and 9500rpm.i have reved my last motor to10 000 by mistake twice but not something i would do on a regular event.gtr 700 revs to13000 rpm and have footage on there site showing it launch at this rpm well woth a look.

[caminperth]

13,000rpm? Thats nuthin - my bike does that easy!

Seriously though - silly revs. I supose some of the answer could be - "because they can"

[zanda]

how does the 8500 to 9500 for rb26s compare to rb20s or 25s and sr20dets?

also, to what extent does the longer throw of a rb30 limit the revs acheivable?

[snyper510]

I am under the impression that the RB26 is the only rb engine with solid lifters? The hydraulic setup of the others is much less suited for higher rpms as (valve float etc becomes an issue).

RB30 -> longer throw = higher peak piston velocities, which is one of the larger factors in determining maximum rpm (time for some forged internals!).

Reciprocating mass, oil spec and quality, cylinder clearances, component composition, etc will also all have influences on what rpm you can achieve reliably.

[summoner]

my RB20 see's it 8500rpm limiter every so often no biggie

[GTS-t VSPEC]

RB25's I wouldn't take past 8000 without doing a solid lifter conversion and forged internals, plus the crank isn't supposed to be as strong, so swapping to an RB26 crank will mean it could handle GTR revs.