Originally Posted By: akela
Originally Posted By: ZeeOSix
That's what the oil pump's pressure relief valve and the filter's bypass valve are for. Oil filter designers don't "control oil flow" with the size of the holes/slits in the center tube. Designers ideally want the oil filter to be as free flowing as possible and still filter as efficient as possible.
If the oil is really thick because it's super cold outside, the flow is controlled when the oil pump goes into pressure relief. The pump creates much more oil pressure trying to force it through the tight engine bearings, and that causes the output pressure to increase until the oil pump's pressure relief valve starts to work.
Keep in mind that the engine's oiling system is about 15 times more restrictive to oil flow than the average oil filter.
I understand that there are pressure relief valve and bypass valve; I just not sure whether they are guaranteed to be efficient enough for the "worst cases".
And I do know that the paper is not as strong as the metal. Rest of the system may be 15 times more restrictive, but 150 times more tolerant to the elevated pressure.
If the pressure relief on the oil pump, and the bypass on the oil filter are designed correctly, then they should be able to take the "worse case" scenario all day long. IMO, an oil filter isn't designed correctly in terms of media and center tube strength if it can't handle delta-p at some factor above what the filter's bypass pressure is set to. In other words, if the bypass valve is set to 15 PSI, the filter should be able to take at least 25+ PSI of delta-p all day long without media or center tube failure.
Originally Posted By: akela
Originally Posted By: ZeeOSix
There are a lot of people who don't really understand how an automotive oiling system works. It's not very complicated, but the missing piece I think most people don't grasp is the workings of positive displacement oil pump, and how it makes and controls the oil flow through the engine.
Definitely, it's not a rocket science. Not sure that the positive displacement needs to be referred to that often.
I think it does have to be mentioned, because how a positive displacement oil pump works and effects the oiling system is an important factor in these "filter flow restriction" discussions. Some guys think the oil flow is due to a constant pressure source like water flow from a garden hose ... but it's not. The only time the system acts like one fed from a constant pressure source is when the oil pump goes in to pressure relief - which is not very often. If the pump isn't in pressure relief, then 100% of the flow from the pump is going through the filter and the engine, even if Filter A is just a little more restrictive than Filter B. That's why engineers can't really control the flow in an engine by trying to restrict the holes in the center tube, unless those holes were almost closed off completely which would force the oil pump to hit pressure relief at a very low flow rate.