N54 crank hub issue - power level?

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Jul 27, 2017
150
#1
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
747
New York
#2
Definitely a tough question. I've seen N54 and S55 spin crank hubs at all different power levels. Its honestly a dumb design imo on BMW's part.
 
Jun 4, 2017
795
#4
Someone had one slip at stock power levels.
 
Jul 27, 2017
150
#5
Mine slipped with bolt ons and inlets on pump fuel
Someone had one slip at stock power levels.
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:
 

Twisted Tuning

Lieutenant
Platinum Vendor
Oct 25, 2016
747
New York
#6
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
 
Jan 24, 2018
457
SC
#7
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
585
West Nyack, NY
#8
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.
 
Jul 27, 2017
150
#9
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.
 
Jul 27, 2017
150
#10
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?
 

kayzrx82

Specialist
Apr 4, 2018
71
#12
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
71
#13
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 .
 
Sep 19, 2018
133
#14
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.
 

Twisted Tuning

Lieutenant
Platinum Vendor
Oct 25, 2016
747
New York
#15
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
 

NoQuarter

Lieutenant
Nov 24, 2017
867
Indiana
#16
Can someone summarize the various solutions we have available from the Vendors?
 
Oct 28, 2017
818
Monroe CT
#17
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.
 

Traf

Specialist
Aug 3, 2017
84
#19
Mine just let go on me on Saturday, the very first time I hit the limiter in 2nd lol
You forgot to mention that your limiter was set to 8k.
 
Last edited:

Hydra Performance

Corporal
Platinum Vendor
Jan 31, 2017
154
#20
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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