Regulated Return discussion
Excursion's 4ever!
Joined: Jun 2010
Posts: 346
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From: Yucca Valley, CA
Same here.
Lead Driver
Joined: Jul 2017
Posts: 6,855
Likes: 2,332
From: WV
I am late to the party on this thread. Used the link to toomanytoys’ thread the other day and really enjoyed the read. Very interesting and thorough work.
I hadn’t considered the fuel bowl as an air removal point but feel this is very accurate. It is located at the highest point with the FPR at the top of the bowl. Pretty good design it seems to me.
Did you already have the Hutch mod? My theory has been the FRx would be be seen as more effective without the Hutch mod. Once the Hutch is completed the air would be evacuated into the tank instead of reintroduced into the pump. I saw a very definite noise level change after doing the Hutch. My wife even noticed.
I think the recycling of air is the biggest factor here. Once the air is in the system it will play round robin until it goes through the injectors. The Hutch mod gives air the escape it needs.
My thinking here, sorry SSJ, is what if those fuel quick connects aren’t as “air free” as you think? Hear me out though. SSJ states that the QC’s rarely cause any issues with introducing air. I believe him as he has performed 100’s of Hutch mods. BUT what if they let air in ever so slightly. Once in with the stock system the air is trapped in the loop. However, with the Hutch the tiny amount of air from the QC’s is released harmlessly into the tank upon return. So SSJ would be correct. With the Hutch mod the QC’s cause no concern.
Thoughts?
This may be true but I really feel this is adding a lot of complexity to a simple system. The fuel rail will still need 65psi. So even if the pump is flowing less, the pressure and at least part of the “work” is still there. I feel the biggest difference to pump longevity would be in upping the pressure it has to produce making it work harder. These factory pumps seem to last a long time.
You do have a point about more volume of fuel potentially introducing more air...
I hadn’t considered the fuel bowl as an air removal point but feel this is very accurate. It is located at the highest point with the FPR at the top of the bowl. Pretty good design it seems to me.
Did you already have the Hutch mod? My theory has been the FRx would be be seen as more effective without the Hutch mod. Once the Hutch is completed the air would be evacuated into the tank instead of reintroduced into the pump. I saw a very definite noise level change after doing the Hutch. My wife even noticed.
FRx doesn’t really ‘eliminate’ air. It just moves it to another place. (See last paragraph below)
.......
Also, if the in-tank mods have not been completed - we are just recycling air back to the fuel pump.
My question is - where does this ‘air’ come from in the first place? We’ve established the factory filter assembly does an excellent job of removing air that could be the result of turbulence between the pump and the filter (or the RARE situation where the pre-pump quick connect fittings leak).
.......
Also, if the in-tank mods have not been completed - we are just recycling air back to the fuel pump.
My question is - where does this ‘air’ come from in the first place? We’ve established the factory filter assembly does an excellent job of removing air that could be the result of turbulence between the pump and the filter (or the RARE situation where the pre-pump quick connect fittings leak).
My thinking here, sorry SSJ, is what if those fuel quick connects aren’t as “air free” as you think? Hear me out though. SSJ states that the QC’s rarely cause any issues with introducing air. I believe him as he has performed 100’s of Hutch mods. BUT what if they let air in ever so slightly. Once in with the stock system the air is trapped in the loop. However, with the Hutch the tiny amount of air from the QC’s is released harmlessly into the tank upon return. So SSJ would be correct. With the Hutch mod the QC’s cause no concern.
Thoughts?
You do have a point about more volume of fuel potentially introducing more air...
Lead Driver
Joined: Jun 2013
Posts: 5,647
Likes: 891
From: north of Minneapolis, MN
SSJ poses a very good question...Where is this air coming from? Turbulence does not create air. It would only cause "air" suspended in the fuel to separate. At some point, air would have to be introduced to the system from somewhere. There is the possibility that sloshing in the tank could allow some air to be ingested by the fuel intake, but that would be minimum unless running very low on fuel. I can see where there would be temporary air introduction when doing things like changing the fuel filter, or otherwise opening the fuel system.
Let's look at another closed system...how about a hydraulic system on say a dump truck? It has a reservoir, high pressure pump, and it circulates fluid and returns fluid to the reservoir. Even when I operated a dump truck that we took a sand spreader on and off of, we never really worried about air in the system...even when connecting and disconnecting hoses regularly. Now, there is not the constant returning of fluid to the reservoir like a fuel tank would have, but during snow and ice events we would leave the PTO engaged in these trucks and drive up and down the highway, so that way we did not have to pull over and come to a complete stop to engage PTO every time we needed to use the spreader...so in that case, there was a decent quantity of fluid circulating constantly. Once again though, never saw any negative effects that could be from aeration of the oil. I would think that hydraulic oil would take longer to clear air also, since it is thicker. Maybe I am completely off the ranch with this comparison, but it seems similar enough.
In the end, the air does have to come from somewhere. Turbulence does not create this "air", it could just make it reveal itself...but it has to be there to begin with.
Maybe a closer comparison would be a gasoline EFI engine...the fuel pressures are around the same, and the system operation is similar..."high" pressure pump pressurizes fuel system, pushes fuel under pressure through the fuel rail, injectors fill, discharge, excess fuel volume and pressure are pushed back to the tank with the use of a pressure regulator. You don't see air introduction issues with these systems...
Let's look at another closed system...how about a hydraulic system on say a dump truck? It has a reservoir, high pressure pump, and it circulates fluid and returns fluid to the reservoir. Even when I operated a dump truck that we took a sand spreader on and off of, we never really worried about air in the system...even when connecting and disconnecting hoses regularly. Now, there is not the constant returning of fluid to the reservoir like a fuel tank would have, but during snow and ice events we would leave the PTO engaged in these trucks and drive up and down the highway, so that way we did not have to pull over and come to a complete stop to engage PTO every time we needed to use the spreader...so in that case, there was a decent quantity of fluid circulating constantly. Once again though, never saw any negative effects that could be from aeration of the oil. I would think that hydraulic oil would take longer to clear air also, since it is thicker. Maybe I am completely off the ranch with this comparison, but it seems similar enough.
In the end, the air does have to come from somewhere. Turbulence does not create this "air", it could just make it reveal itself...but it has to be there to begin with.
Maybe a closer comparison would be a gasoline EFI engine...the fuel pressures are around the same, and the system operation is similar..."high" pressure pump pressurizes fuel system, pushes fuel under pressure through the fuel rail, injectors fill, discharge, excess fuel volume and pressure are pushed back to the tank with the use of a pressure regulator. You don't see air introduction issues with these systems...
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Joined: Dec 2011
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Anyone receive their kit from Kim yet?
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Joined: Jul 2008
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From: N.GA Mountains
Regulated Return becomes ‘deadheaded’ when fuel demand exceeds pump volume...
When fuel pressure drops below regulator pressure - the regulator no longer allows fuel to pass through. Aka ‘deadheaded’.
When fuel pressure drops below regulator pressure - the regulator no longer allows fuel to pass through. Aka ‘deadheaded’.
FTE Chapter Leader
Joined: Jan 2005
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From: Henderson, NV
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From: N.GA Mountains
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Mountain Pass
Joined: Aug 2019
Posts: 177
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From: Abrams, Wisconsin
Since my T4 install I have thought about this. In the moment I felt it was the right thing to do, So i put a RR, 4 line feed and post pump filter setup. My engine bay looks awesome!!! but I have often thought about removing the regulated return and 4 line kit to go back to stock. No issues yet and honestly don't think I will have any. My fuel bowl was starting to leak, and I hate the filter setup honestly. I prefer having my spin on below the truck. Also even in Wisconsin, with proper fuel treatment I dont need the fuel heater.
You guys make me regret doing the 4 line.. Now I have to dig through my totes and find the fuel bowl.
You guys make me regret doing the 4 line.. Now I have to dig through my totes and find the fuel bowl.
Former Vendor
Joined: Sep 2020
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From: Florence, MT
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Joined: Jul 2008
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From: N.GA Mountains
The type of fuel pump makes a big difference in this equation as well.
Looks like the big gerotor-style pumps like FASS and Airdog are the most susceptible to cavitation. Combine this with increased volume and they seem like a bad idea.
The type of pre-pump filter also comes into play. A restrictive, low micron filter increases the opportunity for cavitation/air.
It appears the engineers at International/Ford understood these factors when designing our stock fuel system.
This article describes different pump designs.
https://www.onallcylinders.com/2017/...-pump-designs/
Looks like the big gerotor-style pumps like FASS and Airdog are the most susceptible to cavitation. Combine this with increased volume and they seem like a bad idea.
The type of pre-pump filter also comes into play. A restrictive, low micron filter increases the opportunity for cavitation/air.
It appears the engineers at International/Ford understood these factors when designing our stock fuel system.
This article describes different pump designs.
https://www.onallcylinders.com/2017/...-pump-designs/
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Joined: Jul 2008
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From: N.GA Mountains
I am a fan of 4-port feed. Not a fan of RR. Yet.... Need a more convincing argument that stock/deadheaded is ‘bad’.
5th Wheeling
Joined: Nov 2021
Posts: 46
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I like the idea of the Air Dog 5G in conjunction with a regulated return system and fuel bowl delete. The air dog has an internal bypass to return air entrained fuel to the tank as well as very serviceable filters, the regulated return allows for precise fuel pressure control (Not concerned with the dead head argument) and the fuel bowl delete opens up engine valley space making service to other components easier in my opinon. No claim to performance benefits, other than the removal of air entrained fuel at the air dog system which gives me a warm fuzzy with regards to injector life (Real or percieved).