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Old 09-13-2008, 01:07 PM
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Originally Posted by ScoTFrenzel
Interesting isn't it?

You can prime an engine with a battery drill with cold room temperature oil, and yet some say it takes a million horsepower to turn the pump.

I use a 3/8 electric drill that free spins 2800, and I guess at least 2000 under load (4000 engine rpm)..... and it sure isn't a 12 hp drill.
No, but since the drag on the pump is exponential, (a function of the square of the speed and the pressure based on viscosity) and the pump spins the same speed as the engine (double the cam speed), try spinning that pump to 6000 with some cold 10w40 in the case. Now you've quadrupled the pressure, which (other factors excluded) has multiplied the drag on the pump by at least a factor of 16 - and that is simply from the oil pressure. That doesn't take into consideration the exponential increases in friction on the driveshaft, the drive gear on the cam, and the gerotor friction inside the pump.

People say the same thing about alternators because they spin so freely. Put a load on them and spin them to 5000 rpms and then see how freely they spin.

Oil pumps take considerable HP to run. Otherwise, why would manufacturers use a heat-treated chrome-moly 3/8" shaft to drive it?
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