Quote:
Originally Posted by nkaminar
Just one comment. Joe K in post #14 made a comment that the pressure was not enough to force hydrodynamic separation (of the journal to the bearing). The hydrodynamic separation is caused by the rotation of the journal in the bearing. There is a wedge of oil formed that is dragged along with the journal and this actually does the separation. The pressure that is formed is many times more than the oil pressure, even in a modern engine.
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Neil is quite correct. The sole purpose of oil in the engine is to keep the bearings cool. The fact that it is slippery helps. Guys who race these engines set their bearings with a wider clearance than most of us so that the oil can flow through quickly, carrying heat with it. By supplying oil under pressure to the bearing, more oil flows through it while the engine relies on hydrodynamic pressure to keep the crank journal from contacting the bearing. There is a relationship between the two but they are different.