this is one concept ive never really understood, if for instance we know there are no oil leaks, and the oil pressure is low wouldnt that mean that the flow of oil through the engine is high which is what we want, while if the pressure is really high that means the flow is getting blocked by bearings and what not which would lead to a slower flow of oil throught the block which could lead to failure?
The oil pump provides the flow but not the pressure, well not directly, because without flow there is no pressure.
The oil pumps flow/volume does increase with RPM so pressure will also increase, but the pressure can't exists without resistance.
The oil pressure sender is located on the main oil passage after the oil filter, so there is:
Oil pump->>>----high pressure bypass--oil filter-----sender------bearings.
If you were to cut the main passage after the sender, so there was just flow going past the sender, sender would read 0psi, because there is no resistance/back pressure, oil is flowing out at the same volume it is coming in, so 0 psi.
The pressure is created by the resistance against flow out of the bearing gaps.
When engine is at higher RPMs, so oil pump is providing more flow, the actual oil coming out at the bearings doesn't increase as much as you would think, pressure goes up because incoming flow has gone up but outgoing flow is almost the same, so sender is seeing more back pressure.
If one bearing gets worn the back pressure on the whole systems goes down.
The 2.9l had this issue, cam bearings would wear too much and lower pressure.
If oil pressure is low then gravity prevents it from getting to the top of the engine, so rockers "tick"