Quote:
Originally Posted by Tricki
Ive added the Crank Hub Bolt Capture to my car and to date i haven't heard of a slip with this in place.
A cause is the bolt to back out by the aggressive down gearing especially when tuned in D3 transmission setting.... ( my take )
Ive also added CS transmission flash and it down shifts fantastic and bearly past 4k revs, compared to stock at 6+k revs jolting the car back and possibly putting stress on the Crank Hub.
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You are miss-understanding the failure mode here. The preload on the joint is reduced first then the bolt may back out as the joint becomes looser and looser.
Think of the bolt as a spring. When it is tightened down it is stretched and pinches all the components together. If one of the components moves or compresses the height of the pinched components changes which also changes the bolt's stretch and the amount of pinch force it applies. As soon as you are below a threshold the bolt no longer applies sufficient pinch force to keep the joint together and all the parts spinning together. Each time the bolt can apply less and less preload exacerbating the problem and eventually it backs out.
The hub capture solution is dubious, the only thing it does is link the rotation of the bolt to the crank hub.
However the crank hub is still only fixed to the crank by the bolt threads and bolt preload. The timing gear and oil gear are sandwiched in there and still free to spin with respect to the bolt, hub, and crank. If the gears spin they will remove the preload and allow the whole of the hub and bolt to back out. The crank hub capture
does not increase the preload / clamping force on the oil and timing gears!
The only thing the crank hub capture does is not allow the hub to spin with respect to the bolt. The only thing driven by the hub are the accessories (alternator, AC comp, etc). So if the accessory load is what causes the spun crank hub then the bolt capture is a possible solution, but this seems unlikely.
I think the reason no (reported) captured cars have failed is that 1) these cars are put back together with a lot of care and hence will fall into spec and not be outliers and 2) the failure numbers are relatively small anyways and the number of captured cars even smaller (and those on forums willing to share even less), so it is likely we would not hear about a failed one.
The only solution is to key a one piece hub / gear combo to the crank as Gintani does. Considering the cost of this solution and the fact most spun hubs do not cause much damage I personally will take the gamble and deal with it when it spins.
https://www.realoem.com/bmw/enUS/sho...diagId=11_5597
https://www.realoem.com/bmw/enUS/sho...diagId=11_5626
PS this is not meant as an attack on you merely info I am spreading
EDIT: Some further food for thought, my previous car a MK3 Focus RS had a similar crank hub design.
1) I money shifted it once. Was going for fourth coming out of a chicane at Zolder and got 2nd. Saw over 8k rpm (6.5k redline) on the tacho, car went into limp home mode till I restarted it several times --> no spun crank hub!
2) When carrying out the head gasket recall (common issue, about a year after the money shift) I got the car back with a spun crank hub (dealer swore they timed it right)! This issue is so rare on the Focus RS I no of no other cases of it happening. It was due to the poor reassembly on Ford's side and the fact they reused the crush washer holding it all together (equivalent to part 6 in the 1st link):