Quote:
Originally Posted by chris719
BMW definitely has this data. BMW very likely has probability distribution graphs of the torque required to spin the friction washer. You'll never see it and they will never admit there is an issue with some engines.
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BMW will not have 100% accurate data of which cars failed and why. Trust me I have been the engineer responsible for similar things at different companies and the data we get back from the field is usually pants unless management wants a full investigation into a topic. Even then you are dependent on competent diagnosis and people going back to BMW and not their independent shop.
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.