I respectfully disagree with the thought that air stays on top and does not get sucked into the fuel pick up. Looking into the subject of entrained air, which is tiny air bubbles dispersed throughout the fuel, I fail to see how this would not happen in a moving Super Duty whose fuel is being sloshed around by the very movement of the truck itself. This creates air bubbles into the fuel in the fuel tank. I also found a lot of articles on the subject of entrained air as a contaminant in hydraulic systems. I think we could all agree on the detrimental effects of any small amount of entrained in our fuel at the very high pressures that our common rail fuel systems are using and because that fuel is the lubricant for the pump and injectors.

It took awhile but I found this which I've read before and copied/pasted here before.



From this link:

"Air contamination is very common in a hydraulic system

A contaminant is defined as anything that impairs the performance of the hydraulic system and its components. Air contamination in a hydraulic system can be found in hydraulic fluid in four different forms:

• Dissolved air – hydraulic fluid typically contains 6-12% of dissolved air by volume;

• Free air – for example a pocket of air trapped anywhere within the system. Pre-filling components and proper bleeding of the hydraulic system during start-up will usually eliminate free air;

• Foam – larger bodies of air, typically bigger than 1mm in diameter, found congregating at the top of the fluid; small amounts of foam are usually cosmetic and generally do not cause problems;

• Entrained air – very small bubbles of air, less than 1mm in diameter, dispersed throughout the hydraulic fluid.

The last of these, entrained air, causes the most problems..."



Another good read here.


Go here and search for "entrained air."


From that search led to this.

In that link:

"While many people may be familiar with particle counters and the techniques for measuring moisture in an oil sample, few are aware of the methods for assessing the amount of air in oil or even that air is a serious form of contamination. In certain situations, air contamination has the potential to be very destructive, and its effects on oil and machinery deserve more attention.Air can be challenging to quantify. It may exist as a contaminant in the following states: dissolved, entrained, free and foam."


https://www.theleeco.com/insights/so...aulic-systems/

"TRAPPED AIR AND DISSOLVED (ENTRAINED) AIR

There are two prevalent examples of air found in hydraulic systems: trapped air and dissolved or entrained air. Trapped air inside a fluidic system is typically an air pocket that is difficult to flush out or remove. It can occur during an initial green run (following new production), after system maintenance, or during a key-off event (such as system shutdown); it can also accumulate over time during system operation. Dissolved or entrained air consists of small air bubbles suspended or contained in a fluid; the entrained air bubbles flow through the system in the hydraulic fluid. When the system is stopped, the air can migrate upwards and collect in system passages, creating additional pockets of trapped air."



https://www.dieselarmy.com/engine-te...em-is-the-key/

"Because diesel is a higher viscosity than gasoline, the bubbles do not rise to the surface as easily, the fuel in your tank is drawn up the pickup before the air can rise to the surface. Once in your fuel lines the air entrained in the diesel can form larger bubbles that will interrupt the flow of fuel to the engine."



https://airdogdiesel.com/about/diese...system-issues/

"Why is this? When air bubbles or vapor are present in your diesel fuel delivery system, fuel injection is delayed. This delay happens because the fuel cannot be injected until the air and vapor are compressed to the correct fuel injection pressure. This delayed injection will result in a delayed ignition, loss of power, and unburned fuel exiting the exhaust in the form of black soot and smoke.

How is this? Two words: tank slosh. Tank slosh is the natural movement of diesel fuel within a tank that happens when the vehicle is in motion. This motion stirs up the fuel into a bubbly froth, adding an excessive amount of vapor into the fuel."



I am not saying that these systems, like an Air Dog or a FASS pump, are absolutely necessary to run your truck. I presented this as information only to do with it what you please. For the average person who will probably sell their truck before it needs a HPFP or an injector(s), this wouldn't make sense. But for me, since I plan on driving my truck for a long time, I'd like to try to make the expensive fuel components last as long as possible.

I have heard that once the Air Dog is installed, the engine will seem to idle smoother and MPGs may go up slightly due to pure fuel with no entrained air present which gets the injection timing back spot on. We will see... I will post up the install and what I experience once driving with it.

Bottom line, I am Overkill after all...

 

Also want to add this to the discussion.

Micro-Diesel Combustion of Entrained Air in High Pressure Fuel Injection Systems 2018-01-5019

Modern high pressure diesel fuel injection equipment (FIE) is designed to operate with high quality fuel that is free of external contaminants. Undissolved bubbles of air that are normally managed by the low pressure fuel delivery circuit, may be present for a variety of reasons. Any bubbles that persist will violently implode following entry to the high pressure system. The effects of bubble collapse under conditions close to atmospheric pressure are well documented as cavitation collapse. The objective of the present paper is to study the implosion of air/vapor bubbles in diesel fuel when exposed to much higher pressures under controlled conditions resembling those in modern FIE. The results demonstrate that the adiabatic temperature rise is sufficient to initiate combustion, causing visible light emission, damage to nearby materials and formation of black carbonaceous precipitates in the fuel. Similar black precipitates have been previously reported in the field.

Real time sensors indicate that micro-diesel combustion of air bubbles in fuel has several distinct phases, which appear broadly analogous to those experienced by fuel-droplets in air in a conventional engine. These include compression, ignition delay, combustion and finally quenching as the applied pressure and resulting temperature are reduced. Two distinct combustion phases were observed: a bright but brief initial phase followed by a more extended period of less intense light emission. It is suggested that these are due to the auto-ignition of premixed vapor, followed by a more gradual diffusion controlled flame respectively. The effects of micro-diesel combustion were eliminated below a critical air volume, most likely due to the entrained air going into solution prior to attaining the minimum pressure required for auto-ignition, highlighting the importance of effective air management in real applications.

Another link from Parker Racor.

 

My understanding is diesels use very little fuel while idling so if this is true I don't see much of a risk unless you were filling up a tank that is almost empty. And if coming off a hard run it is nice to let turbo cool down (which happens at idling) before oil flow stops.
Again I rarely fill up my fuel tank under half full.
The biggest reason to idle while filling up with fuel is when it's hot and you have passengers it keeps them cool.
Although with this discussion I might be motivated to upgrade my fuel tank to a 60 gallon.

 

Just thinking out loud here but if the entrained air is such a hazard I wonder why they haven't tried to come up with some type of fuel cell like used in race cars. That would take care of any fuel sloshing.
I realize all of this is way above my pay grade lol

 

In the most atrocious technical explanation I can come up with, things would be OK if the fuel pumps were allowed to fart (let off the compressed air due to bubbles).

That said, I'm still not convinced that air bubbles are a problem. I don't know that an hydraulic system is a fair comparison to a diesel fuel system. But I'm really looking forward to the Air Dog install that Overkill will be doing. How the heck you can objectively measure the results from that (other than MPG or hp/tq) is something I would like to hear more about.

 

Maybe the comparison to a hydraulic system is not an apples to apples, but I wanted to bring it up.

In reading all this stuff, plus my overkill mentality, I just believe the benefit to using one of these aftermarket pump systems is to rid the fuel of all the entrained or dissolved air. Not being an engineer or scientist here, I'm not saying I know exactly the correct terms for said air but it seems that air in the fuel throws off the injector timing. Air is mentioned as one of a few contaminants in diesel fuel. Another plus I would be believe would be that with pure fuel being sent to the HPFP, the combustion should be more efficient and that would mean (could mean I guess) less soot (which is actually a product of incomplete combustion if I'm remembering correctly).

In the videos I have seen, you can see when the fuel in the tank is agitated, the fuel being drawn into the system by the pump looks cloudy from having air present. And the aftermarket pump then removes the air. The result is that the fuel flowing out of the aftermarket pump looks clear -- the air is gone.