IML: Re : pressure vs volume
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IML: Re : pressure vs volume



This comes up all the time in various forms. Follow along....your oil pump is a positive displacement pump meaning it can move a set amount of oil each time it rotates, whether it is a spur gear style or a rotor style like Chrysler uses. So for EXAMPLE, if it can displace an ounce of oil for each revolution of the pump it will move 1000 ounces at 1000 engine rpm. Now, if the various clearances in the engine bearings, crankshaft, connecting rods, lifters, pushrods, let less oil past them than the pump can move you will get pressure.

If this doesnt seem clear, remember that we are talking FLOW here, and resistance to FLOW causes PRESSURE. Dont think so..go turn on the garden hose and let it run, youll see flow. Then put your finger over the end of the hose and close it off about half way, you reduce the flow but increase the pressure. Its not quite the same as the kind of flow vs pressure you see in hydraulics where there isnt any leakage desired because in an engine its a given that you will have oil leaking past the various clearances in the engine, thats how it is designed. The oil cools as well as lubricates.

This is also why as an engine wears out the pressure will drop, because the clearances get larger as the bearings and other surfaces wear. Since the pump can still only move a set amount of oil, whatever that amount is, the resistance to the flow of the oil lessens and the pressure drops accordingly.

Use a high volume pump as opposed to a high pressure pump. The only difference between standard and high pressure is the relief spring and you dont need higher pressure anyway. A high volume pump will give you more than enough oil flow to create good oil pressure.

Mikey
62 Crown Coupe


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