You didn't pre-fill your HPX line?

As I asked Joe, if there was really that much flow through the line, wouldn't it stand to reason there would be some measurable (performance wise) consequence for not having the line (lack of oil in one head)?

 

I don't know that there is a large amount of flow through the line, but I know from experience that you can drain it, install it, drive less than 200 miles, and it will be full of oil when you remove it again. That's certainly cycling it enough to keep it from stagnating.

 

Brad... not which direction, but whether or not the flow is large enough to push the oil through for "changeouts" as a result of imbalanced head rail pressures. Dan (and maybe others as well) have brought up some excellent points about the impact forces from the pulsations, but I'm still not yet convinced that the pulsation band width is long enough for the full volume of the HPX line to become displaced by "fresh" oil. There is no doubt that the pulsation packs one heck of a whallop, but that whallop may not be for a long enough time to clear the line before the other head pulses back with its own pulsation whallop.

I am also convinced that the air from the initial install is completely displaced over some operating time frame, but that still does not mean that the entire volume of that original air bubble is displaced during the injector firing sequences.

I'm going to pull a "Gene" move, now. I made the last statement in the above paragraph because the air in the line is at atmospheric pressure (say 15 psi for round numbers), yet under engine operating conditions, that air is compressed to about 2,000 psi. Using the Ideal Gas Law, the pressure P1 multiplied by the volume V1 at one condition is exactly the same value of the pressure P2 multiplied by the volume V2 at the second condition.

P1 x V1 = P2 x V2

For a 3/8 inch line, assuming 12 inches of length, the interior volume is roughly 14 cubic inches, which is V1 for the above equation. As already mentioned, P1 is roughly 15 psi.

Therefore, 15 x 14 = 210.

Since we already knkow that P2 is approximately 2,000 psi, you get the volume occupied by that same initial air space under opearting conditions by dividing (P1 x V1) by 2,000.

.... since P1 x V1 = 210, V2 = 210 / 2,000, which then gives you a V2 volume of 0.105 cubic inches.

Since the cross sectional area of the 12-inch lone HPX line is only 1.17 square inches, the length of the original 12-inch long air bubble is reduced to only 0.089 inches, or only a little over 1/8" or 2.2 mm.

Now that you can see that the original air bubble is so greatly reduced in size (from 12 inches to 2.2 mm), it would not take very much oil movement to push that air into the oil rails, and then through the injectors and back to the sump. HOWEVER.... in order for the entire volume of oil to get displaced with the injector firing sequence, there would have to be 14 cubic inches of oil pushed through in a back-to-back firing sequence for injectors 6 and 8 - 14 cubic inches is the same as 7.7 fluid ounces, which is almost half a pint of oil.

So we can see that the air is easily displaced, but that may be due ONLY to the compressibility of the air, and not so much because of the volume of oil pushing back and forth.

Now, I'll admit that I rounded a few numbers for easier math, and I also assumed an inside tubing/hose diameter of 3/8 inches, a tubing length of 12 inches, and an operating pressure of only 2000 psi. A smaller tubing/hose diameter or length would obviously make the above volumes smaller, but higher operating pressures would make the volume smaller.

NOW... WHO can tell us how much oil would be displaced by the sequential firing of a single injector. How much oil volume is pushed through the injector for each firing event?

If we can get that answer, we can then see if the volumes get pushed through the hose or not.

 

Wow Jason, party foul dude. Just because I choose to change the air in my tires to keep it from getting stale does not mean everyone should.

 

Welcome to the party, Mike.

 

Assuming you don't see the tiny bubble from Pete's calculations, then that would imply there is plenty of oil flow, but not explain the lack of symptoms for those not running the HPX.

Here's Mike's secret click here

 

The size of the bubble under pressure is irrelevant, it still has to be moved out the end of the HPX into the rail.
Where is the air bubble going to be located assuming no flow?
How much flow will it take the push the bubble from the center of the HPX out into the rail?

 

I need to go spend some time with the family. I'll check back in either later tonight or in the morning.

 

The size of the bubble is not irrelevant. It is exactly the whole point of this discussion. The smaller the bubble is, the less oil it takes to move it, and the more likely it is that it will get moved out of the line. We already know, though, from voiced experience that the air does get removed. We just don't know if it gets removed because of a "just enough flow" movement, or by wholesale volumetric replacement in the line.

Also, assuming that the bubble is captured in the center of the low spot doesn't make sense. Air naturally tries to move upward in a fluid stream, and may even split into two bubbles with one going towards each head. Once at the top of the elbow on the hard fitting, it just doesn;t have much farther to go before it might just get pushed out. another factor working against the assumption that the bubble is in the center is the assumption that has to go with it, and that is that each head see an identical increase in pressure at exactly the same time, but we know that cannot be true due to the firing order/sequence of the different injectors. The first head to get the pressure will preferrentially move the bubble towards the other side.

Gotta run. Goodnight all.

 

Please explain to me what magical process makes it easier to move because it is smaller? A single molecule in the center has to move just as far. It takes less oil to displace it, but if there is equal pressure from both ends it will remain in the middle.

 

Here's the answer:
The injectors don't fire at once, right? Therefore, when one injector fires, oil FROM BOTH OIL RAILS fills the space left from the one injector firing. Then, another injector fires, and again oil FROM BOTH RAILS is pulled in to fill the space. As this happens over & over & over, the oil is moved between the rails through the hose. Is that a good enough explanation? Yes, I'm sure some oil is moved back & forth, but there is enough movement overall that no oil is left stagnating in the HPX.

 

Magician Joe explaining "the magic"! Well done, sir.

It's exactly what I was trying to say earlier when I stated, "The first head to get the pressure will preferrentially move the bubble towards the other side."

What that means is exactly what Joe said... as soon as the first injector fires, there is a void volume that creates a low pressure in that head's oil rail which will be partially compensated for by the higher pressure from the other rail until either 1) the HPOP can make up the difference or 2) an injector in the other head fires.

 

...and what it means is that exactly as advertised, the HPOP output is more evenly used between the two heads. It's not like one side will be very low while the other side is high creating constant flow. I see it as pressure in one head dampening the loss of pressure when an injector fires in the opposite head, smoothing out the demand on the HPOP, which in turn smooths out the engine.

And I KNOW mine idles smoother and is somewhat quieter with it there. Who knows if there is a performance gain (or loss), but it definitely makes for smoother, quieter 7.3. And I notice it right away when I hear the 7.3s at my Guard Unit running. Of course, neither of them has the LL AE injector knock, and I notice that right away, too.

 

And it has also moved half the volume of the oil in the HPX. It will not move the bubble and leave the oil behind. So when the bubble and oil is moved toward one end, fresh oil moves in the opposite end. The oil gets exchanged, there is no stagnation.

 

I understand what you're saying, clux, and cannot disagree with that logic at all with two exceptions.

1) I'm not yet convinced that ALL of the line's volume is displaced with the injector-HPOP action, so I cannot yet say that there is NO stagnation. I can accept that at least some of the line volume is displaced, but don't have enough facts to know how much.

2) "it has also moved half the volume of the oil"... we cant say that just because a buble got displaced. When you look at the "M" shape of the line, any air buble will rise to one of the top peaks in that line, if not split into two bubbles with one going in each direction. This is just the nature of an air buble in any fluid, pressurized or not. Once the bubble has migrated by its own bouyancy to the top of the fitting, it doesn't take much of a volume "push" to shove it down into the head. That said, the movement of oil through the line is not the only thing moving the bubble. HOWEVER, if we invert this line so that any "accumulated residue" (if there is any) can drift back down into the heads once the engine is shut down, under those conditions the air buble will have nowhere to go until the entre line volume gets displaced because the air wants to sit at the highest elevation possible.