10-12-2019, 01:53 PM | #23 |
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Same here, I've asked and they haven't had any m2C spun crank hubs and there are alot of M2C's where I live, and the dealerships are all owned by the same car conglomerate. Also alot of oil cooler failures probably because of the crappy post winter roads, and the fact that no one knows how to drive a low car in my area.
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10-12-2019, 02:04 PM | #25 |
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10-13-2019, 08:05 AM | #27 |
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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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10-14-2019, 09:28 AM | #28 | |
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If BMW does not just use a table to design the bolted joint then I agree with you that they will have some kind of probability distribution of the bolted joint pre-load and friction force and hence how many are prone to failure. I remember testing cylinder head joints and being surprised how great the preload spread could be between the same style of bolts, torqued by the same guy, in the same way. |
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10-14-2019, 10:20 AM | #29 | |
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I wish we had some kind of analysis showing the designed/intended load on the hub and the calculated safety factor. As an engineer, I’m sure you are aware of how many anomalies you see in the field that just doesn’t make sense. |
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10-15-2019, 01:25 PM | #31 | |
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Also there has also been speculation that it's due to more things on the s55 being run off of the timing chain such as the water pump and two hpfps vs. 1.
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10-15-2019, 01:40 PM | #32 |
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10-16-2019, 06:45 AM | #34 |
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That's hard to watch.
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10-16-2019, 07:35 AM | #35 | |
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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): Last edited by Megator; 10-16-2019 at 07:43 AM.. |
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10-16-2019, 08:12 AM | #36 | |
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Then maybe review Gintani solution if keeping long term. |
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10-16-2019, 08:48 AM | #37 | |
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can you simply explain this to me? |
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10-16-2019, 09:23 AM | #38 |
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TBH the vtt spline lock solution sounds promising too, plus you don't have to pull the motor apart to the same extent for drilling the crank.
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10-16-2019, 10:06 AM | #39 | |
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Not without being face to face (or me drawing a pretty picture). However maybe try a little experiment. Take a bolt (preferably of a bigish diameter) and stack a bunch of flat washers on it, then tighten them all using a nut (barely tight, just enough so the washers do not move). Now spin/move the washers without spinnig the nut (this might be hard to do but the more washers you have the easier it should be to do the middle ones), eventually you should be able to get the nut to come off without needing tools.
Essentially this is what is happening with the crank hub. Quote:
Aside from that it seems their machinist might not be of the highest quality, see here: https://www.litchfieldmotors.com/blo...ank-hub-issue/ |
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10-16-2019, 10:23 AM | #40 | ||||
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10-16-2019, 11:42 AM | #41 |
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10-16-2019, 11:56 AM | #42 | |
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In regards to machinist issues, again I've never heard of that from an unbiased third party.
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10-16-2019, 12:29 PM | #43 | |
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I do seem to remember that VTT did not provide any proof as to their success. ie I would expect them to show a pic of a "grabbed" crank that shows the scarring caused by the splines. I have heard it is not a viable solution from various sources though. EDIT: BTW you might be being a bit duplicitous, on the one hand you do not trust suppliers yet trust what VTT claim? |
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10-16-2019, 01:28 PM | #44 | |
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No I don't trust VTT either but I wanted to point out there that a new vendor who wants to market their product by bashig someone else's work while copying VTT's crank bolt capture probably is fishy. Honestly imo it's hard to trust any vendor on this issue especially after tpg screwed everyone over with their sub par product as documented in the thread I linked earlier.
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