Who believes you really need 10 PSI oil pressure....

[joespanova]

All the references to "oil cooling" ..........
In a wet sump I don't see how pressure has a relevance to "cooling"?
In a dry sump , maybe...but a wet sump?
In any event , I ended up using a std. pressure bypass spring which should give me a range of pressure suitable for what I'm doing.........based on the fact that the bearings always looked very good at tear down.......... with the same spring ( std ).

[Kevin Johnson]

All the references to "oil cooling" ..........
In a wet sump I don't see how pressure has a relevance to "cooling"?
In a dry sump , maybe...but a wet sump?
In any event , I ended up using a std. pressure bypass spring which should give me a range of pressure suitable for what I'm doing.........based on the fact that the bearings always looked very good at tear down.......... with the same spring ( std ).

That is straight forward. Ceteris paribus, if entrained gases can be driven into solution by raising the pressure of a system then that fluid will be able to accept rejected heat more efficiently. Foam makes a poor coolant -- bit of an exaggeration.

[Warp Speed]

All the references to "oil cooling" ..........
In a wet sump I don't see how pressure has a relevance to "cooling"?
In a dry sump , maybe...but a wet sump?

Pressure has a reference to oil flow, and flow is what cools parts, no matter the system.

[Kevin Johnson]

Pressurized oil with free air bubbles flows very well, thank you. It just has a lower heat capacity. One step forward, two steps back.

[Brian P]

Oil circulating through the engine picks up heat. Viscous drag in the bearings shows up as heat added to the oil flung off. Oil flung at the bottom of the pistons - sometimes directly via piston squirters, other times indirectly - picks up heat from the piston before it gets flung off again. There is most certainly heat-management associated with oil being pumped around the engine. It doesn't necessarily have anything to do with air entrainment. That's bad if it happens, but heat transfer happens regardless.

Through work,I'm seeing the new technology in oil pumps... a vane pump with a pivoting eccentric outer ring, with the displacement regulated electronically; this allows the pressure and therefore the flow rate to be matched to engine speed and load while minimizing power demand to operate the pump. Lots of newer engines (and transmissions) are like this.

[Kevin Johnson]

Lots of newer engines use engine oil as a hydraulic actuating fluid; look at the Porsche patents -- it is an oblique subject but air is a no-no. Air entrainment is largely a side effect of sloppy engineering that has been tolerated for a long time.

[joespanova]

I can't see the difference in "oil in sump" temps being lower enough to make a difference...............sorry , I just dont see it.
So with clearances on the .003--.0035 range you are suggesting the difference between oil flowing at 80 psi is going to be measureably cooler than the same system / clearances at 50psi?
No way.

[MadBill]

The higher pressure increases the flow rate so that at a given temperature delta within the bearing, more of the heat generated there can be carried off. Wet or dry sump, the temperature will stabilize (hopefully at an acceptable level) at some point, but the bearings will run cooler at the higher flow rate regardless. Visualize the opposite extreme: A small sealed volume of oil surrounding the bearing, with zero flow in or out. The temperature will just go up and up...

[joespanova]

The higher pressure increases the flow rate so that at a given temperature delta within the bearing, more of the heat generated there can be carried off. Wet or dry sump, the temperature will stabilize (hopefully at an acceptable level) at some point, but the bearings will run cooler at the higher flow rate regardless. Visualize the opposite extreme: A small sealed volume of oil surrounding the bearing, with zero flow in or out. The temperature will just go up and up...

Bill.........I get it....theoretically..........I just am not buying that in "reality" there is a measureable difference........sorry.

[Kevin Johnson]

The higher pressure increases the flow rate so that at a given temperature delta within the bearing, more of the heat generated there can be carried off. Wet or dry sump, the temperature will stabilize (hopefully at an acceptable level) at some point, but the bearings will run cooler at the higher flow rate regardless. Visualize the opposite extreme: A small sealed volume of oil surrounding the bearing, with zero flow in or out. The temperature will just go up and up...

Bill.........I get it....theoretically..........I just am not buying that in "reality" there is a measureable difference........sorry.

If you are measuring the temperature of a stabilized system why would you expect to find a difference? It is up to you, the engineer, to take advantage of the increased capability of the system. The rate at which the delta T can be decreased is the advantage -- assuming non-aerated oil. If you do not reject the heat from the system (oil pan) to the environment (air -- car; water -- boat) as rapidly -- or more -- then that is yet another way to lose any advantage.

For emissions purposes it is an advantage to raise and stabilize the system temperature as rapidly as possible. This is normally not a consideration on SpeedTalk.

[Warp Speed]

The higher pressure increases the flow rate so that at a given temperature delta within the bearing, more of the heat generated there can be carried off. Wet or dry sump, the temperature will stabilize (hopefully at an acceptable level) at some point, but the bearings will run cooler at the higher flow rate regardless. Visualize the opposite extreme: A small sealed volume of oil surrounding the bearing, with zero flow in or out. The temperature will just go up and up...

Bill.........I get it....theoretically..........I just am not buying that in "reality" there is a measureable difference........sorry.

That's not theory....that is pretty much the way it is!

I watch oil flow, oil pressure, oil density ect., at differing rpm's and temperatures in race engines all day long. If you are purely riding on the empirical observation side of things, that is the way it is!

There are two reasons for oil. Lubrication and cooling.
It only takes so much flow to provide the needed lubrication for a given load. Cooling this load over time takes quite a bit more.

It's far from being theory!

[clshore]

The higher pressure increases the flow rate so that at a given temperature delta within the bearing, more of the heat generated there can be carried off. Wet or dry sump, the temperature will stabilize (hopefully at an acceptable level) at some point, but the bearings will run cooler at the higher flow rate regardless. Visualize the opposite extreme: A small sealed volume of oil surrounding the bearing, with zero flow in or out. The temperature will just go up and up...

Please explain how a fixed displacement pump running at a given RPM can exhibit different flow rates ...

[MadBill]

Two ways:
1. Less back pressure at the bearings means less upstream pressure at all other 'leak' points in the system, thus less flow through them = more for the bearings.
2. The effective displacement (net oil volume delivered out of the pump) varies with the position of the bypass valve, which typically recirculates within the pump body and so does not contribute to delivered volume.

[340king]

There is actually a thermal balance equation that needs some attention here. The work that goes into compressing that oil more adds heat to the oil. So the oil coming out of the pump at a higher pressure has to be at a higher temperature. So once it reaches equilibrium temp, it may well be higher. The key point to all of this is that the corollary is probably more important. If you are well over that 10 lbs per 1,000 rpm rule of thumb, you are probably wasting energy in the oiling system.

[Belgian1979]

The higher pressure increases the flow rate so that at a given temperature delta within the bearing, more of the heat generated there can be carried off. Wet or dry sump, the temperature will stabilize (hopefully at an acceptable level) at some point, but the bearings will run cooler at the higher flow rate regardless. Visualize the opposite extreme: A small sealed volume of oil surrounding the bearing, with zero flow in or out. The temperature will just go up and up...

Please explain how a fixed displacement pump running at a given RPM can exhibit different flow rates ...

Not at a given rpm...at a given rpm, the pump has X amount of flow. But the flow increases linear with the rpm.