N54 crank hub issue - power level?

MoreBoost

Corporal
Jul 27, 2017
181
This is probably a question without a specific answer but at what power (or more likely torque) levels can the crank hub spinning become an issue?
 

Twisted Tuning

Lieutenant
Platinum Vendor
Oct 25, 2016
828
New York
Flippin heck. That's crazy. I thought only people on big power would be seeing the issue.

Maybe these are rare cases?

I've been running about 550 to 600 whp for close to 2 years. Sounds like it could go at any time :anguished:

i wouldn't say rare nor would i say it's an epidemic when it comes to the crank hubs spinning. It's merely a design/engineering flaw that by the nature of the design is something that can definitely happen at any time.

However, i personally have not done research on this specific question, as i never had the urge, but maybe someone knows. Is the N54, N55, S55 interference or non interference engines. i would assume non, since i have seen people spin crank hubs. and simply reset the timing and drive on. If they are non, then honestly, i can kinda understand why they designed it that way, however, still should have been a solid or keyed part at a minimum IMO
 

ShocknAwe

Lieutenant
Jan 24, 2018
594
SC
What I'm more curious about is how the fixes in development for this issue have been tested and proven to actually prevent this from happening.
 

veer90

Lieutenant
Nov 16, 2016
835
West Nyack, NY
i wouldn't say rare nor would i say it's an epidemic when it comes to the crank hubs spinning. It's merely a design/engineering flaw that by the nature of the design is something that can definitely happen at any time.

However, i personally have not done research on this specific question, as i never had the urge, but maybe someone knows. Is the N54, N55, S55 interference or non interference engines. i would assume non, since i have seen people spin crank hubs. and simply reset the timing and drive on. If they are non, then honestly, i can kinda understand why they designed it that way, however, still should have been a solid or keyed part at a minimum IMO
They are absolutely interference engines. Whether or not there's valve damage depends on how far the sprocket slips.
 

MoreBoost

Corporal
Jul 27, 2017
181
What I'm more curious about is how the fixes in development for this issue have been tested and proven to actually prevent this from happening.
Basically it's a case of putting the fix on and then running various scenarios to see if it doesn't happen any more.
So high power runs at the drag strip. Like Maximum PSI or dyno and spirited drives like Tony at VTT have done.

From F8x forums it seems like hitting the kick down (on DCTs) is the most common cause of the hub slipping. Probably really jolts the motor and the chain. There's just a friction washer preventing the sprocket from slipping on the hub, as well as the hub screw holding everything in place which can back out.
 

MoreBoost

Corporal
Jul 27, 2017
181
I wonder if that's what appears like VANOS errors when some people's car's throw codes during WOT tests.
Also wonder if VANOS adapts should the chain manage to slip on the sprocket or is the slippage of a single tooth by the chain on the wheel catastrophic?
 
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kayzrx82

Specialist
Apr 4, 2018
91
i wouldn't say rare nor would i say it's an epidemic when it comes to the crank hubs spinning. It's merely a design/engineering flaw that by the nature of the design is something that can definitely happen at any time.

However, i personally have not done research on this specific question, as i never had the urge, but maybe someone knows. Is the N54, N55, S55 interference or non interference engines. i would assume non, since i have seen people spin crank hubs. and simply reset the timing and drive on. If they are non, then honestly, i can kinda understand why they designed it that way, however, still should have been a solid or keyed part at a minimum IMO
It is an interference engine. the exhaust valves usually get the short end of the stick. if it slips a little you can get lucky but it can a slip so far off that it throws timing to the point something has to give. Mine ended up bending 6 exhaust valves.
 

kayzrx82

Specialist
Apr 4, 2018
91
Basically it's a case of putting the fix on and then running various scenarios to see if it doesn't happen any more.
So high power runs at the drag strip. Like Maximum PSI or dyno and spirited drives like Tony at VTT have done.

From F8x forums it seems like hitting the kick down (on DCTs) is the most common cause of the hub slipping. Probably really jolts the motor and the chain. There's just a friction washer preventing the sprocket from slipping on the hub, as well as the hub screw holding everything in place which can back out.[/QUOTE

I think its a combination of several things. Sudden inertial changes to whatever is being driven by the hub. Sudden deceleration of the crank while the cams , accessory drive and harmonic dampener want to keep spinning. Increased Harmonics from increased cylinder pressures. Increased load on the cam from increased cylinder pressure causing more load on the valve train. Ive heard some people say BMW did the crank hub this way as a fuse. I highly doubt that you can fuse a critical timed part like this and it makes no sense to fuse it. What could fusing this part possible save? I believe it was more for cost savings on the crank (faster and easier to machine) and faster and easier assembly by a robot at the factory. Its the stupidest thing to hope friction can keep the motor in time. It really needs to be keyed like the older BMW engines or machined into the crank like the s65 and s85 .
 

Optigrab

Corporal
Sep 19, 2018
133
I wonder if that's what appears like VANOS errors when some people's car's throw codes during WOT tests.
Also wonder if VANOS adapts should the chain manage to slip on the sprocket or is the slippage of a single tooth by the chain on the wheel catastrophic?
This is an error listed for MSD80

Diagnosis of mechanical chain jump
P0016, P0017
The diagnosis is performed after the reference position adaptation. The learned position of each camshaft signal edge is stored in the non volatile RAM of the ECU as an adaptation value. Before storing the value, the new adapted value is compared with the stored value. If the deviation exceeds a max value, the error CAMχoneχtoothχoff is delivered to the error management and the new value is not stored in RAM. With this diagnosis a chain jump of the timing chain is detected.
 
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Twisted Tuning

Lieutenant
Platinum Vendor
Oct 25, 2016
828
New York
They are absolutely interference engines. Whether or not there's valve damage depends on how far the sprocket slips.
It is an interference engine. the exhaust valves usually get the short end of the stick. if it slips a little you can get lucky but it can a slip so far off that it throws timing to the point something has to give. Mine ended up bending 6 exhaust valves.

Thanks for the info. Then that makes the crank hub design that much worse, lol. SMDH
 

Rob09msport

Captain
Oct 28, 2017
1,052
Monroe CT
Is this something that is more likely on higher mileage or is it kinda like s55 where after certain point your chances of survival increase lol. Like is it more of inconsistent holding power of grip disk on a case by case or does it just fatigue and go over time. Trying to decide If I will never go over 600 if I should do capture , something more , or leave it alone unless it ever gets touched.
 

Hydra Performance

Corporal
Free Vendor
Jan 31, 2017
233
You forgot to mention that your limiter was set to 8k.
Not so loud they'll hear you! :p

In all seriousness though, crank hub slippage is more a function of rate of engine acceleration or deceleration (or both in the case of the limiter), not so much peak rpm.
 
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