Mazda Filter

A gerotor pump is positive displacement. Used on commercial chillers for chilled water systems also (larger, but still the same design.). It may be output controlled in the Skyactive engines but it is, in fact, positive displacement.
 
I looked up the Mazda engine online. The oil pump is a cartridge unit that is bolted on below the block. It has a solenoid inside which, schematically, controls what's directed at the bypass valve which is also built into that cartridge. Solenoids indicate computer control. The computer's ability to shunt oil from one side of the gear to the other clearly means the volume of oil coming out of the oil pump can be modulated by a computer.

Vane and piston pumps in other applications are also 'positive displacement' if you ignore the adjustable housings and piston strokes, respectively. Some call those systems "pressure-compensated." That simply means the output flow from the pump is varied in order to maintain a target pressure. If I was trying to speak to the broadest possible audience, I might call that a pressure-based system, because that is exactly what it is in terms of fluid flow from the pump.
 
As said earlier, a pump is either positive displacement or it's not based purely on it's mechanical design and how it moves fluid through it. There are many different pump designs that are positive displacement.

In a system with fixed flow resistance fed by a PD pump, the flow volume and pressure at any given point within the system are directly correlated if the fluid viscosity and pump efficiency are held constant. A pressure sensor could actually be used as a calibrated flow meter knowing the fluid viscosity and flow at the pressure sensor's location for example. So the pump could be controlled by volume output or by pressure at some point in the system ... the end result will essentially be the same, but it's easier to control based on a pressure sensor as volume sensors are not as simple to incorporate.
 
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This is what I have been thinking about since the very first OEM filter I bought for my wife's CX-5. I am good with the OEM filters.
 
All filters are important. What most people seem to miss or discount is that the oil filter is the only filter that removes debris that gets in the oil from whatever source. The air filter no matter how good doesn't prevent debris from contaminating the oil.
 
In a system with fixed flow resistance fed by a PD pump, the flow volume and pressure at any given point within the system are directly correlated if the fluid viscosity and pump efficiency are held constant.

I'll only try once more. Do try to follow.

The oiling system is not positive-displacement on the SkyActive-G engine, meaning the volume of oil which enters the engine is NOT fixed in relation to engine RPM. It is modulated by the ECU.

Don't react for a moment, just think. Let that sink in. The volume of oil which enters the engine is NOT fixed to engine rpm.
 
I'll only try once more. Do try to follow.

The oiling system is not positive-displacement on the SkyActive-G engine, meaning the volume of oil which enters the engine is NOT fixed in relation to engine RPM. It is modulated by the ECU.

Don't react for a moment, just think. Let that sink in. The volume of oil which enters the engine is NOT fixed to engine rpm.
"The volume of oil which enters the engine is NOT fixed to engine rpm."
^^^ I never claimed it was the same. Just defining what a PD oil pump is (started in post 57) ... regardless if it's a variable volume PD pump or not.

Again ... you really don't seem to understand what the actual definition of a positive displacement oil pump really is. A pump is either a positive displacement or it's not - it's purely a mechanical design attribute of the pump. A positive displacement pump can also be a variable volume pump (controlled mechanically and/or electronically via ECU which I've already commented on) while still being a positive displacement pump. That's what you're not computing.

What you are trying to describe is a variable oil volume fed oiling system. But here's the part you don't get ... an oiling system like that with a variable displacement oil volume is still using a positive displacement oil pump with a controlled variable volume output. "Don't react for a moment, just think. Let that sink in." :)
 
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It’s a PD pump with a two-stage bypass activated by a solenoid. It’s super simple. The ECU can command either ‘low’ or ‘high’ oil pressure depending on RPM and load.
 
And regardless, if the oiling system can't supply adequate volume to the engine when there's an ADBV in the filter, then something is seriously wrong with the oiling system design.
 
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