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      09-26-2012, 10:35 AM   #42
BMRLVR
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Drives: 2011 E90 M3,1994 Euro E36 M3/4
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Quote:
Originally Posted by CSBM5 View Post
What the heck is going on with the S65? Is this the suspected bedplate deflection causing this? Any ideas?

I don't think these main bearing issues are a result of BMW's poor understanding of tribology but instead are a result of potential design issues in the block structure itself (i.e. seeing greater than expected deflection at extreme rpms that disrupts the bearing oil film? It wouldn't take much to make a significant problem rear its head). The natural attack is to blame the bearing/oil film/oil used/etc; however, I'm wondering if a much more significant issue is at the root of these problems...
The issue is most likely the fact that the engines are assembled too tight, i.e.: The main bearing oil clearance is insufficient. I would highly doubt that there is a deflection issue since the bedplate looks to be a very robust and rigid piece...... Much more rigid than what individual main caps would be.

The bearings in the pictures, although worn, are not excessively worn and definitely would not be causing significant oil pressure loss and definitely not be causing the ticking noise that many people are claiming is main bearings. The top layer of babbit is not even completely worn through but is polished quite a bit. When bearings are excessively worn they show the copper/bronze layer and many times have quite a bit of grooving and or discolouration due to heat. The whole purpose of the babbit layer on a bearing is for it to be able to touch the journal and/or to absorb contamination and do no damage to the journal in the process.

Another thing that may indeed cause bearing wear to these engines (or any engine for that matter) is high load before the engine oil is up to temperature. In my personal vehicles, I never use high throttle openings or place high load on my engines before the oil is at operating temperature, especially my M3! Even after the variable redline allows you the full 8400RPM I don't feel the oil is yet warm enough, personally I like to see my oil at around 85-90 degrees Celcius (185-195 degrees Fahrenheit) before I attempt any high load or high RPM. Any engine of ours that is required to be started and put at full load immediately (Back-Up Power, Pumps, or Emergency Vehicles) have engine heaters on them that keep the fluids (oil and coolant) at operating temp 24/7

The engine in the pictures would have lasted a long time before having any issues, and quite frankly, that wear may have occurred early in it's life and no further wear would have likely occurred once the clearance it needed was achieved. Any
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Last edited by BMRLVR; 09-26-2012 at 11:00 AM.
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