I am just wondering what oi pressure is dependent on?
Is it revs?
Is it the oil pump?
Is it the pressure sensor?
Is it the temperature of oil?

What controls the oil pump to push out the variable pressure?

 

I got this answer from "the guru"

The oil pump is driven by a chain that is driven by a sprocket off the crankshaft. As the engine turns faster, so does the crankshaft, then the sprocket, then the chain, then the oil pump drive gear. The faster the engine rpm, the higher the oil pressure. It's max pressure will be reached at an rpm when the flow of oil can no longer exert any additional pressure due to the oil pump seals, the passage size that the oil passes through, etc. This is why max oil pressure can be reached before max rpm is reached.
Oil pressure is also dependent upon the viscosity of the oil and this is dependent on the temperature of the oil as cold oil can be "thicker" and more viscous than hot oil. Of course, then we have "multigrade" oil, which we routinely use. Even though a cold mutigrade oil will still have good cold flow characteristics, once it is pumped and flowing, it can still exert good oil pressure. This is why after your car has sat outside in the cold for hours, the first 10 - 15 minutes of driving will show very high oil pressure, even at moderate rpm. This is also why Honda put in a cold temp rpm ceiling - so we don't do damage by extremely high internal oil pressures, which can blow seals and gaskets.
Cold oil = higher viscous oil = higher pressure.

 

One other thing. Most cars, if not all, have a mechanical device (spring actuated check valve) that limits oil pressure as well. This valve is like a turbo wastegate for your oil system to prevent too much pressure from happening.

The cold RPM "ceiling" on our cars I thought was more of overall engine protection as opposed to having too much oil pressure.

 

[QUOTE]Originally posted by RWD_RCKT
[B]One other thing.

 

Here is a theoretical question...

How much higher without the check valve? 150psi?

 

[QUOTE]Originally posted by RWD_RCKT
[B]Here is a theoretical question...

How much higher without the check valve?

 

The bypass valve is part of the oil filter, right? If I'm remembering correctly, not all oil filters have it.

I would expect that the oil pressure would easily exceed the regulated pressure of the bypass valve if it is cold.

 

Well I can tell you that an 84 Colt Vista (basically a 2.0L 8V Mitsubishi motor) that has that valve blocked will run 135psi at 6000RPM when cold derived from an Autometer gauge that only read up to 100 psi. That is the only reason I even know about the valve.

I figured 9000RPM would send it sky high....



And no the Vista was not my car.

 

[QUOTE]Originally posted by gernby
[B]The bypass valve is part of the oil filter, right?

 

Here is Marcucci's oil filter review (Here). He cut open quite a few brands of filters, and rated them. It looks like all of them have "Bypass Valves". I think the Bypass valve allows oil to bypass the filter element if oil pressure reaches a certain level. I guess this is to prevent the filter media from being blown out.