HPOP Oil System Pathways:
The inlet to the reservoir is the large standpipe that ends just short of the top cover. This is to prevent drain back of the reservoir.
The standpipe is feed by two sources of oil. The first is the feed from the low pressure oil pump through a passage way in the front of the engine and through the anti-drainback check valve. The 2nd source of oil is from the left side lifter gallery.
The oil is feed into the reservoir to supply the HPOP. The supply to the HPOP is the hole in the bottom of the reservoir. There is also a small air bleed hole in the reservoir that returns oil back into the crankcase. The reason that the reservoir never seems to fill when you’re manually filling is the two holes, the air bleed hole and the standpipe itself that let oil bleed back into the left back oil gallery until the oil is level with the top of the standpipe.
The IPR returns oil from the pump into the front cover below the reservoir, but enters a standpipe that runs through the casting of the reservoir and dumps back into the front cover to lubricate the HPOP and cam gears and then returns to the pan. The IPR does not, like many think, return to the reservoir. This oil is super heated from being compressed, and needs to be cooled.
The reservoir holds about ¾ of a quart. The rate at which the reservoir is changed has nothing to do with the injectors or the chip program. This oil is changed at a fixed rate based on the output of the pump. Remember, it’s a fixed displacement pump. The injectors useage is feed to the rails, with 100% of the balance of the HPOP’s output being sent back to the crackcase through the IPR. There is absolutely no way any oil spends any length of time at all in the reservoir. If you want to get real specific…. The oil also leaves the reservoir through the air bleed hole from pressure from the LPOP. This is not a fixed rate since the hole is a fixed orifice and the reservoir pressure varies based on engine rpms. That amount could be very significant.
The rate of exchange (that the HPOP is responsible for) could be figured pretty easy. A stock late model pump moves about 6.8 cc’s per engine revolution. At 800 rpms (idle), the pump is displacing 5440 cc’s or 5.78 quarts per minute!!!! At 3000 rpms, that same reservoir is exchanging its contents at a rate of 21.5 quarts per minute. That means it replaced the reservoir sump contents with oil from the pan in 2 seconds. This is why there are no formal directions from Ford or International on how to change this oil. It’s not a conspiracy guys.
The other area of oil in the HPOP system is the actual rail. These consist of the flexible lines from the HPOP to the heads. The heads have a machined gallery that runs the length of the head to hold pressurized oil for the injectors. Each injector intersects this rail. This is a dead end system. This means that there is only one entrance and one exit. The oil has only one way to go. The only exit is the injector. These rails hold about ¾ quart of oil each. These empty or exchange at the rate the injectors “consume” it. I use the word consume, but it doesn’t burn the oil, it uses it to actuate the hydraulic portion of the injector. Unlike a traditional hydraulic piston that recycles the fluid internally in the piston body, the HEUI injector uses the oil needed to extend the plunger, which expels fuel, but on the retraction stroke, expels the oil into the top of the head to drain back into the oil pan. So, the larger the injector, the longer the pulse width, and the more time you spend at WOT, etc, all play a part in how fast these rails exchange their contents. This calculation is more difficult, based on too many variables. However, it is not 7:1 as I have seen someone mention. This is the multiplier to injection pressure and has nothing do with the actual volume of oil. Suffice it to say, the oil in the rails doesn’t hang around long either.
Bob
