I'm not talking about a water pump, I'm talking about positive displacement pumps...I teach hydraulics, VERY well aware of how they work. A fixed volume pump displaces a fixed volume PER ROTATION only...spin it faster, higher volume.....Belgian1979 wrote: ↑Fri Dec 31, 2021 2:39 am These are positive pumps, not like a water pump.
If the pump puts out a fixed volume depending on rpm and it is only limited by the spring which bypasses excess volume (which it is), the fact remains that what goes in must come out. If you consider the engine to be a fixed orifice as a whole, when you have more restriction your bypassed volume in the pump goes up. If you have less restriction, your bypass reduces.
As such if you have a restriction and the pressure P1 from the pump is higher, the pressure what remains after the restriction (P2) will equally be higher in the same amount (the pressure reduction will be the same as the restriction itself has not changed). As the volume of a fluid cannot change, the speed by which is passes through the engine has to increase.
As such I'm starting to doubt that oil limiting pushrods might work. A reduction in pressure by changing the spring would be more effective.
Using a std volume pump would evidently also reduce the volume, but it would only reduce the bypassed volume as I would have to assume there would be enough spare capacity to build pressure.
Now, the bypass spring/valve is NOT the only limiting factor. The leak rate of the engine is the main one, and it changes slightly with heat....oil gets thinner, clearances increase...not much but a little, and it does have an effect. As the pump rpm increases, the amount of oil circulated through the engine increases until the volume exceeds the leak rate's ability to keep up....THAT'S when the bypass becomes active, and it's only active until the pressure drops below it set point, then it closes. It will open and close very quickly, as once a large leak is created, the pressure drop is instant....
Something else to think about, oil pressure is much overstated....What would you rather have, an oiling system that can reliably deliver X amount of flow to the bearing surfaces under all conditions, but at a lower pressure, or a higher pressure that cannot? Pressure in an oiling system is not an end all be all solution. A very large percentage of the time, especially on BBC and SBC engines, a high volume pump is a waste of money.....The stock pumps are more than capable of supplying sufficient oil under all conditions. Only when excessive or increased clearances are used does a higher volume pump become needed, and that's just to overcome the leak rate........
On my dry sump on my dragster, you'd think the pump would move a massive amount of oil....it does not. The pumping element isn't much different in size than a standard bbc oil pump.....I run 9 quarts in my system...7 in the tank and the other two in the engine....I have a huge oil pan and the majority of the remaining oil is there when the engine is running....I can set the system to deliver more than 100 psi, but all that does is cost me hp, and does nothing for improving oil flow.....right now it's set to 70 psi and my bearing look better now than they did when it was at 100....
As to the original question about oil on top, if you're filling valve covers with oil, it's not a pump or sump size problem, its a RETURN problem, and that needs to be addressed. In more than 30 years of this stuff, I've NEVER ONCE SEEN a pan pumped dry as so many state......And that's on street, off road, and racing engines running just about every type of pan there is, from max rpms of about 3500 to more than 8000........
