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Old 02-13-2017, 05:49 PM
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Join Date: Feb 2006
Location: Gore. New Zealand., SI
Cobra Make, Engine: DIY Coupe, F/T ,MkIV.
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Quote:
Originally Posted by olddog View Post
There are High Volume pumps and then there are High Volume High Pressure pumps. To make a high volume pump they simply put in wider gear teeth and it pumps more volume. Roughly 10% more, from what I have read. The oil pump has a pressure relief valve that is spring loaded. Put in a stronger spring and wallah you have a high pressure pump. 75 PSI would be a high volume high pressure pump in my opinion.

So the PRV spring will not allow the oil pressure (in your case) to go above 75 psi, no matter what oil, what temp, what rpm, because the PRV lifts and allows some of the oil that the pump is pumping to dump back into the oil pan. So how much oil is flowing to the engine and how much is flowing back to the pan? Once the oil pressure reaches the limit and the PRV lifts to regulate the oil pressure, nobody knows the answer. Or can it be figured out intuitively?

We now know that your PRV is set to 75 psi, so we can assume any time your oil pressure is below 75 psi that the PRV is closed, and all the oil is pumping through the engine. Since it is a high volume pump, we can assume that your engine is getting 10% or so more volume that it would have gotten with a factory pump.
One correction in schematic description, virtually no domestic USA engines have the oil pump pressure bypass direct excess oil back to the pan, they all seem to flow back into the inlet side of the pump, this must play havoc with the inlet stream being drawn up the pickup tube... bit like trying to crawl up a kids slide while someone squirts you with a high pressure hose from time to time. Side oiler FE is about only one I can think of where that rear pressure relief gets returned to pan.
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