Kevin Johnson wrote:clshore wrote:Guys, please stop and think a minute:
Oil pumps are positive displacement devices.
Each turn of the pump flows the *same* volume (except for internal leakage, which is minor).
So unless you have a variable speed oil pump, the *volume* is always proportional to the RPM.
Figure the cu in (or cc) per revolution, and multiply by RPM/2 (if driven from cam) to get pump flow.
The idea of measuring the amount of bypass oil is a good one, but the pump is still going to flow same.
With respect to rod bearing flow, you are neglecting the centrifugal force imparted
against the flow on the approach in the circuit in the
rotating crankshaft to the closest proximity to the crankshaft longitudinal axis of rotation. There will be some minimum pressure required to overcome this force that varies with rpm. If the minimum pressure is not met there will be no flow despite the presence of oil pressure from the pump.
There are other ways to provide oil to a crankshaft so any of these discussions should be prefaced with an understanding of the circuit involved and the rpm in question.
Kevin, I understand what you are saying, but my point is that the pump swept volume is fixed per revolution.
That amount of oil WILL flow, unless the HP needed to drive the pump exceeds the motor output, or the oil pump drive breaks, or the pump body explodes.
The oil itself will not compress in any meaningful way.
The amount of pressure developed is precisely determined by the motors' internal resistance to that flow, ie sum of bearing clearances, oil squirters, oil passage hydraulic resistance, etc.
So if internal centrifugal force must be overcome for the oil to flow, it will show up as increased system pressure at the pump outlet.
The oil will flow no matter what.