Quote:
Originally Posted by kawasaki00
It is less than the minimum clevite spec. .75 would be .0014 clearance. I have measured myself quite a few that were .0012-3. Even going off the clevite spec it is still wrong. Clearance is only half that spec though, the oil must be mated to the clearance. RPM, torque all must be taken to account. The problem with the .0013 clearance is it needs to be mated with a 20wt oil like a honda accord. But they dont turn 8500 and they dont make the power either, therefore no way would I try to run a 20wt oil in the m3.
So could you run that clearance spec, sure honda and toyota do it all the time but they also run 0w-20
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Yes, surely the combination of load, rpm, clearance and oil are all strongly related. I also completely botched the simple division of RGs updated numbers in my prior post (point #3). The result from his nominals is 0.66 thousandths in/in, about 10% tighter than the minimum Clevite spec of 0.75. Despite this, I still believe firmly in my point #4 in my prior list (and all of the other points). Your point about measuring some nominals even tighter is largely irrelevant. Again all assemblies in all industries have tolerance stack, there will be a nominal, some will be loose and some tight. The existence of numbers smaller than the mean is a truism, not a damnation that BMW screwed something up. That observation is universally true for all engines. Again, what is the formula, relationship, observed data, etc. for bearing/engine longevity vs. bearing clearance? Surely moving toward too large of a clearance could be equally bad for engine longevity, but we have no real data there either.