Originally Posted By: 09rexwagon
I've been meaning to research a bit more on the operation of an oil pump and some oil fluid dynamics so I can understand you and (Superbusa) better. But do you have any visuals that describe the pump relief and what that means? I'm assuming this is a completely separate concept from the filter.
I think there were various threads where all this was hammered out ... you'll see that me and Gary have many points we don't seem to agree on. Could just be terminology ... don't care anymore, and I think Gary has me on "ignore" now, so he can't even see my postings anymore anyway.
I'll see if I can find one thread where (member called chunky) made some nice schematics showing the oil system, etc.
Edit -- read this thread, and search for others. There are many similar threads out there that will make your head hurt ... mostly the ones where Gary and I are trying to agree on things. I'm sure you'll quickly figure out who makes more sense.
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1519777&page=1
Originally Posted By: 09rexwagon
So if the oil pump is being pushed too hard and it can't seem to pump the oil fast enough (ie the pressure rises too high...the engine can't use the oil as fast as the engine is TRYING to make the oil pump, pump it), there is a relief valve that diverts some of the oil on the high pressure side of the pump either back into the sump or back into the flow volume on the vacuum/low pressure side? And then, I'm still confused on how this concept meshes with the oil filter bypass.
You are correct on the oil pump's pressure relief valve. It's meant to LIMIT the oil pressure the pump puts out to the engine. Say it's set to 80 psi ... that means the pump can only put 80 psi of pressure on the inlet of the filter/engine flow circuit. Well, imaging holding the supply pressure to 80 psi and varying the oil viscosity. You can see that less oil volume (GPM) can be pushed through the circuit at 80 psi when cold and thick than if the oil was warm and thin. If the oil gets thin enough, the pump will actual go out of pressure relief and the pump's output pressure will go below 80 psi. If you have an oil pressure gauge in you car you can see this happening as the oil warms up. You might see the gauge pegged at 70 psi at high RPM with cold oil, but only pegged at 60 psi at high RPM after the oil is hot. In this example, when the oil is hot the oil pump is not getting into pressure relief territory anymore, because the gauge is no longer indicating 70 psi. The delta between the pump's relief pressure of 80 and the gauge pressure of 70 when the pump is in relief is the PSID across the filter, as most oil pressure gauges are located between the filter and engine inlet.
Originally Posted By: 09rexwagon
Also, when you guys say PSID, is that an acronym or is that just pounds per square inch differential across a boundary? (we call that delta P across a boundary so it is non discriminating on units of pressure
).
Anyway, some reference reading/diagrams would be helpful.
Yes ... PSID means "pounds per square inch differential" ... meaning the "delta pressure" in PSI across the filter media.