It's called "Priority Mains" in other engines. Here's an illustration: On start-up, the oil pressure forces the vertical plunger down, allowing oil to hit the main galley almost instantly by flowing upwards through passage "C", but since it didn't pass the cooler, in your system, that amount is not filtered. Once pressure is established at the main galley, the oil flows through passage "B", adding pressure to the spring and closing off the pump feed to passage "C" and forcing oil to flow up though passage "A", through the cooler, to the bearings with excess pressure dumped via downward oil flow in passage "C", out the horizontal plunger-valve; very clever.Martin Benade wrote: ↑Fri May 03, 2019 7:48 pm I have that setup and I think it is said to be unfiltered when the pressure relief valve is open, meaning full filtering almost always.
In the stock system, (keeping in mind Vic's comments regarding the output of the pump)this happens pretty much as soon as the pressure light goes out, meaning something like 99.9999% of the oil the bearing see is filtered. I have no idea whether the length of the hoses has any effect on the time required.
In order to avoid any change at all to the stock lube engineering, the Pre Mat parts break the flow immediately at the pump output and return it at the same place, filtering 100% of the oil: