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Originally Posted by serialk11r
:P I'll take that lightheartedly.
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It was meant lightheartedly. :happy0180:
You're obviously a very bright guy, you just have the confidence of youth.
Quote:
Originally Posted by serialk11r
old greg do you mind sharing your wisdom? :P
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Well, since you asked nicely...
Honestly, I'm really not an engine guy. Most of the stuff you guys talk about in that area goes right over my head, but I do know a bit about bearings.
Main and rod bearings are hydrodynamic bearings, they operate due to relative motion, not oil pressure. Oil pressure is required only because, as you mentioned earlier, the bearings are not sealed. The basic theory is that when the crank is not quite concentric with the bearing (due to load) the relative motion between the crank and bearings is trying to drag the oil through too small a gap for it all to fit. This creates a pressure differential and a force that counteracts the load without the crankshaft actually touching the bearings. The closer the crank gets to the bearing (higher load) the more force is generated, and the higher the speed the more force is generated for a given crank/bearing gap.
Lugging occurs when the load on the crankshaft (from cylinder pressure) is high enough that oil alone can not provide an equal reaction force and the crankshaft contacts the bearings. It happens because there is not enough relative motion to support the load, rather than not enough oil pressure.