Quote:
Originally Posted by DrFerry
Could there be a different reason why nearly 100% of the blown S65s coming your way - with rod bearings greater than stock clearance - are blowing up? In other words correlation is not necessarily causation. Example: stock engines with stock OEM bearing clearances also blow up - and most S65 engines have already had the rod bearings replaced with a well known solution i.e. extra clearance bearings which increases the probability that the population of engines you receive will have extra clearance bearings.
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We discuss survivorship bias every time we table this conversation in the shop- the evidence points towards that not being the whole story
Stock high-mile motors (150k) coming in with rod bearings about to have a Disco Party, and main bearings showing moderate wear.
Vs.
Low-mile motors with replaced rod bearings, coming in with the front main welded to the crank and the rest of the mains in TERRIBLE condition, while all of the rod bearings look brand new despite their 10-30,000-mile life in the motor. I go into more detail on why this appears to be happening (based on math and theory, until we do more testing) in my first response ITT.
Quote:
Originally Posted by tdott
Quote:
Originally Posted by Partee Racing LLC
but the point is that larger clearances require more oil pressure to ensure a sufficient oil wedge.
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This BE point comes to mind when you mention pressure but not flow:
"Having double oil flow over the bearing surface increases the wedge strength and keeps the bearings cooler. " |
Quote:
Originally Posted by DrFerry
Quoted from the link below which is packed with test results and in great depth information on this topic.
https://www.m3post.com/forums/showthread.php?t=1337998
"But the resulting oil flow is nearly double with BE Bearings over the BMW 702/703 bearing counterparts. Having double oil flow over the bearing surface increases the wedge strength and keeps the bearings cooler. The results with BE Bearings seems to be a huge win, much bigger than any of us expected." |
Anyone in this industry knows that "pressure" is often used interchangeably with flow or volume because there's no realistic way to measure flow in the system without installing a dedicated device. This is just rarely ever a distinction that is made because it is unheard of for an engine to run on such a knife-edge of oil flow volume that it matters- any other engine we do has enough oil flow that it hits the bypass pressure and stays there once you're beyond idle.
It is obvious that Peter meant flow here- sharp shooting that is weaponized pedantry and is beneath this discussion, especially from two forum members I respect.