# 7200-8000 rpm imbalance in rb26?



## koopa (Aug 18, 2005)

i cant remember where i read this but it was mentioned that there is a problem with the harmonics of the Rb26 when you rev past 7200rpm on a standard engine due to vibrations affecting the crank. Apperently it can cause engine failure taking the engine to this rpm.

I dont tend to drive my car past 7000 rpm 99.9% of the time but i thought as nissan have set the factory rev limit at 8000rpm it should be ok to take the engine up to this speed? 

Can anyone shed some light on this?


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## JapFreak786 (Aug 29, 2003)

IIRC there is something along those lines

buy a Bee*R controller mate,don't need the cut to be set at F to damage your gaskets.

Our GTR is set at 7500rpm,and the cut is set to 2 so it's very mild


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## R1 Nismo (Feb 25, 2005)

The original specification on th RB26 crank was 8350rpm. You are right not wanting to over stretch your engine but you should be able to use 7-7500 rpm quite happly, but lots of people choose to change up earlier some later. 
One problem new owners have is they dont know how thier engine was used before they took ownership so they can be slightly more cautious.


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## koopa (Aug 18, 2005)

cheers for the advice guys,

I never have taken the car right up to 8000 but on occassion i have seen it got to about 7800rpm on a spirited drive. Ah it was in an interview with Ron Kiddal!  

im pretty sure my car was used mildly before i took it. It had done 21k miles and had one previous owner. The car was bone stock with no mods at all when i bought it. 

The Bee R controller seems like a good idea. Will it make a huge racket tho when i hit the limiter?


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## Amaru (Aug 24, 2004)

Have seen many RB26's with standard cranks and rods with a set of ARP bolts and forged pistons that regularly travel to the 8250rpm limit (and quite alot raise the limit to 9000rpm for occasional use). I have never ever seen one fail due to rpm/bad harmonics.


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## LAURENCE (Jan 4, 2005)

Yeah stock rod bolts are a concern at high rpm, the crankshaft does wander around quite a bit at the 8,000 rpm level (one tuner used a clever microscope to detect movement), stock turbo's are running out of puff then too, breathing is too, so no harm in changing earlier if you've hit your peak power.

Aftermarket Rev limiters do make a bit of a racket but its not Anti-Lag/Rally loud.


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## Totalburnout (May 15, 2005)

koopa said:


> The Bee R controller seems like a good idea. Will it make a huge racket tho when i hit the limiter?


give me a phone hombre


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## koopa (Aug 18, 2005)

i would but i deleted your number by accident gayness


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## Totalburnout (May 15, 2005)

ask your mother for it then!   

if your not working this weekend give me a shout and i'll come over and show you the limiter.


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## Mookistar (Feb 5, 2004)

apparently the factory tacho overreads by nearly 500 rpm too IIRC


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## Hedgehog Dodger (Jul 13, 2004)

I think you will find your peak power to be around 7/7500 anyway, so you might as well change gear then.


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## Pulse D (Mar 26, 2005)

Hedgehog Dodger said:


> I think you will find your peak power to be around 7/7500 anyway, so you might as well change gear then.


I Agree....

I was also told by a builder of Skyline engines (he also used to design cranks) that the harmonic inbalance mentioned above isn't the main problem. It's the standard oil pump that can't pick up enough oil to support those revs....


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## leggus (Feb 15, 2006)

Yes, i drive my car sensibly most of the time.. but i have to admit, at Rotorstock i had it banging off the limiter more than once  Seems to have survived that ok tho 

**touches wood**


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## leggus (Feb 15, 2006)

Its like theres a demon overpowers you... i was lined up next to R34 GTR of 'Birmingham Transformers'.. i thought to myself 'theres no way this is gonna show my R32 up', so in stage, punched throttle to limiter then let go.. back end was bouncing, (apologies to my poor rear diff).. limiter every gear  

And hence, wasnt shown up


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## leggus (Feb 15, 2006)

Oh, apart from the fact that after the quarter, Brembo's on 34 had stopped him easily to take the first exit back to pit lane.. my crap standard 32 brakes struggled to stop me before Stratford town centre


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## koopa (Aug 18, 2005)

[email protected]! top bloke lol


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## raaaaaaay (Jun 5, 2006)

Hi folks, just reading this post, tested my car a couple of weeks back to see where the limit was. Hit at 8600 RPM on the standard counter. Is this a bit high for a standard motor? Since that time I have regularly taken it above 8000 RPM without a problem, apart from downpipe working lose and popping the radiator.


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## Pikey (Feb 19, 2004)

8600 sounds about right for a REAL 8000rpm.

Im running an R33 crank and new std oil pump, ARP rod bolts, bottom end balanced - 8000rpm no problem in 12 months :clap: 

Not sure I'd be happy with a bone stock R32 bottom end at 8000rpm though.


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## David (Apr 25, 2003)

Pulse D said:


> I Agree....
> 
> I was also told by a builder of Skyline engines (he also used to design cranks) that the harmonic inbalance mentioned above isn't the main problem. It's the standard oil pump that can't pick up enough oil to support those revs....


If that were true I can’t believe Nissan would have let it out of the factory with an 8000 rpm rev limit as they would have had a huge number of engine warranty claims.

I think it is more likely an internet myth. Unless anyone can come up with some facts?

A possible explanation may be that when tuned the GTR may be able to pull increased acceleration forces so that oil moves away from the pick up and then causes oil starvation that is apparent as bearing failure at 7500 rpm. Just an idea


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## Peter (Jun 27, 2001)

I think it may be a result of us expecting a car which made 280bhp from the factory expecting it to cope with double that without consequence....


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## BBD (May 30, 2002)

> Yeah stock rod bolts are a concern at high rpm,


hmm last time I checked con rods are studs, bolts for crankshaft, and bolts for the head for the standard RB26

Oh yes most aftermarket con rods come with bolts instead of studs not v nice


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## Hugh Keir (Jul 25, 2001)

Part of the problem with unbalanced engines comes from the design of the CAS ( cam angle sensor ) which is belt driven and suffers from harmonics and is therefore incapable of supplying accurate ignition timing, esecially on a high powered car.

Poor ignition timing then leads to further imbalance in the engine since not all cylinders are firing with equal punch, that further interferes with the drive to the CAS.


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## Nocturnal (Nov 5, 2004)

So if you have an uprated oil pump, but on standard crank, where would you place your rev limit.

For us single turbo guy, dyno stop at 7500 but power still raising. Is there a way to get more torque to the lower rev by cam timing? Otherwise, driving past 7500rpm is the only way to get more out of the turbo.


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## AJFleming (Feb 25, 2003)

Wasnt it only a problem to rev beyond 7500rpm if your using higher than standard boost, or am I just making that up?


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## BBD (May 30, 2002)

inline engines are more balanced than V engines by nature and boxer engines are even better.

Reved the car all the way up to 8,100rpm standard without any problems when I started pushing more power and engine harmonics came to mind just went out and bought the ati damper kit from HKS that comes with main crank, alternator, and water pump pulleys.

With either single or twin setup u can run 9k+ with the right set of cams and decent headwork



> So if you have an uprated oil pump, but on standard crank, where would you place your rev limit.


stock engine stock limiter


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## R33_GTS-t (Apr 27, 2005)

Mookistar said:


> apparently the factory tacho overreads by nearly 500 rpm too IIRC


Yep. I change no later than an indicated 8000rpm, which is actually 7500rpm. I do notice a change in note at 7700rpm, which would correspond to 7200rpm.


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## R33_GTS-t (Apr 27, 2005)

leggus said:


> Oh, apart from the fact that after the quarter, Brembo's on 34 had stopped him easily to take the first exit back to pit lane.. my crap standard 32 brakes struggled to stop me before Stratford town centre


I find opening the windows to be more effective above 100mph.


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## tyndago (Oct 24, 2002)

Nocturnal said:


> So if you have an uprated oil pump, but on standard crank, where would you place your rev limit.
> 
> For us single turbo guy, dyno stop at 7500 but power still raising. Is there a way to get more torque to the lower rev by cam timing? Otherwise, driving past 7500rpm is the only way to get more out of the turbo.



Lots of different things here.

Concerns

1. Stock rod bolts
2. Stock oil pump
3. Crank harmonics
4. Stock CAS
5. Stock oiling
6. Stock tach

Fixes
1. As rpm increases the load on the rod bolts increases. Better rod bolts, better rods Here - ARP explains it a lot better than I could. http://www.arp-bolts.com/Tech/Tech.html

"It is seen that the design load, the reciprocating weight, depends on the square of the RPM speed. This means that if the speed is doubled, for example, the design load is increased by a factor of 4. This relationship is shown graphically below for one particular rod and piston."










2. The stock oil pump gears break due to cavitation at the inlet side of the pump, best I can figure. Better ones break less, but still break.

3. All cranks move around. ATI damper supposedly helps that out. On a big power car, with big revs, I have split a couple of stock dampers.

4. CAS. Some is probably due to the stretch of the belt, some due to the 360 teeth pickup on the wheel.

5. The stock pan doesn't hold enough oil. The stock oiling setup slings too much oil up into the head. Under hard cornering the oil pump sucks air. When you suck air, you spill insides of motor outside.

6. The stock tach reads about 400 rpms off.

I have reved stock cars to 9,000 rpms when I knew no better. Mis-shifts see an incredible amount of revs.

The Nismo oil pump is good out to 8400 rpms or so for race conditions. More for pedestrian cars.

The real issues with piston speeds, and rod loads don't get too crazy on an RB26 until 10k or so.


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## Nocturnal (Nov 5, 2004)

Well, here is the engine list of my car.

Forge Piston (88 bore)
H section con rod
trust sump extension
Not sure on rod bolt, but it couldn't be standard can it?
Not sure on oil pump again, but then it couldn't be standard with a trust sump?
Not sure on crank, but lets assume it is standard.

given the list, what do you think is an acceptable of REAL rev (rev off the ECU reading)? 7500? 7800? 8000?


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## tyndago (Oct 24, 2002)

Nocturnal said:


> Not sure on rod bolt, but it couldn't be standard can it?
> Not sure on oil pump again, but then it couldn't be standard with a trust sump?
> Not sure on crank, but lets assume it is standard.
> 
> given the list, what do you think is an acceptable of REAL rev (rev off the ECU reading)? 7500? 7800? 8000?


Stock the limiter is 8k. The question is, where does the car stop making power.

I would say for most stuff 8250 prms isn't an issue. For dyno pulls , during USCC, I have spun stock oil pump up to 8750 rpm to get more area under the curve.
It is an issue however if you mis-shift. Datalogs say big 4 digit numbers on mis-shifts.

With 2530's, stock cams, we make the same power at 8200 as we do at 6300. Peak at 7200. The extra power at the top gives you more flexiblity with shifts.


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## Nocturnal (Nov 5, 2004)

I guess I have to take it to a proper dyno for a remap.

On my current dyno, the T45s turbo is still trying to make power when it stop at 7500. What can be done to shift the power band down the RPM range and make more area under the curve? It is using HKS 272 step 1 CAM. I also have a set of Tomei 260 Poncam on order, any suggestion which profile is better?


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## tyndago (Oct 24, 2002)

Nocturnal said:


> I guess I have to take it to a proper dyno for a remap.
> 
> On my current dyno, the T45s turbo is still trying to make power when it stop at 7500. What can be done to shift the power band down the RPM range and make more area under the curve? It is using HKS 272 step 1 CAM. I also have a set of Tomei 260 Poncam on order, any suggestion which profile is better?


Going to the Tomei cams would be a step backwards. More duration, more lift is better for out little 2568cc motors.

As far as shifting the power curve, you can put a smaller more efficient turbo. Put some nitrous on it. Increase the displacement.

Cam timing can shift it down a little, but most singles dont really light off until 4500 rpms or so.

Rev it to 8200 rpms, that way you will be higher in the rev range in the next gear. It won't be as laggy, as you will fall back to an area where the motor is making good power.


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## Nocturnal (Nov 5, 2004)

Well, the 4500 seems to be spot on at where my turbo is at.

The question is, is it save to rev to 8200? Not all the time, but 8200rpm is alot of rev for a turbo inline 6.... We are not talking about a B16a here.  

Granted, it isn't hitting 8200 everytime I shift (unlike when I drive the CRX), so I think I am just trying to find my "UPPER" limit here.


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## tyndago (Oct 24, 2002)

Nocturnal said:


> Well, the 4500 seems to be spot on at where my turbo is at.


Yep.... thats about where they go. About then you are making good exhaust energy.



Nocturnal said:


> The question is, is it save to rev to 8200? Not all the time, but 8200rpm is alot of rev for a turbo inline 6.... We are not talking about a B16a here.


Is it safe to start the car ? Is it safe to get out of bed ? Safe to stay in ? 

Honestly - the difference between 7500 rpms and 8200 rpms would not be huge, but it will make it a bit more fun to drive.

The RB26 has a short stroke. 73.7mm. 8k stock. Its a well put together stock engine.


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## tuRBy (Feb 8, 2006)

can any knowlegable self mechanics or tuners help:

i had no idea the Stock tach reads 500rpm lower than it should, why is this? can it be fixed to be accurate- or would an aftermarket tach make any difference?

would the RPM reading from the Power FC commander give a 'true' rev reading?

So if my peak power on a dyno map is 7100rpm, i should wait untill the stock tach reaches 7600-7700rpm untill shifting up to hit the max power? 

so far i have been shifting at a standard tach indicated 7200rpm, which is 6700!? i do have a power fc commander but so far havent lookd at the rpm readout as i thought there was no point as theres a standard nissan tach on the dash.....


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## Luckham (Nov 10, 2005)

tuRBy said:


> would the RPM reading from the Power FC commander give a 'true' rev reading?


Yes, apparently the PFC RPM reading is accurate.


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