Quote:
Originally Posted by OldBiker
There might be some cavitation at the impeller, but I doubt it. The cavitation we are talking about (imprecise choice of words) is happening in the pickup tube. The theory being it sucks some air/froth as a result of braking/turning in. But the shape (and according to me the bulbous mid-section) prevents it from quickly re-establishing good flow to the pump.
Imagine sucking fluid through a straight straw... if the straw loses contact with the fluid, you will suck air, but flow will resume immediately as the straw is immersed again. But consider a straw with a big bulb in the middle... it takes longer to re-establish flow because the bulb is full of air now and has to be drained--its pressure must fall sufficiently below ambient to suck up the oil... and a larger volume of gas takes longer... especially since the pump impeller is designed for low-volume hi-pressure operation in fluid, not sucking on air. Just a theory...
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What you're referring to is loss of prime on the pump suction. However, for a positive displacement pump, this isn't an issue because guess what? When your car is turned off and you turn it on, the pump will start and suck up oil from the pan. Unlike centrifugal pumps, they can self prime.
What pushes the fluid up the intake is the atmospheric pressure within the system. Liquid doesn't move to a void, it gets pushed from an area of high pressure towards the void.
The issue here is that you don't want to lose suction flow mid corner at high load.