EFII Fuel system in Batt compartment

[spirit49]

I always planned to install the fuel pumps/filters in the compartments below the forward yoke. But its super tight to make it all fit.

Since I'm planning to use a Firewall mounted battery, I'm thinking it makes more sense to use this cavity for most of the items and the pipes.

The Fuel selector might be some cm further away then planned, but should still be easily reachable.

Any reasons why this could be a bad idea?


Espen

 

[Freemasm]

Depends

Are planning on Avfuel only or going to burn car gas?

AvGas = no expected complications. I am doing a similar install/configuration in an RV4 variant. I am trying to build-in the ability to use car gas if I need to; thus, keeping suction losses at a minimum. I chose the Aerolab filter/gascolator for a couple of reasons; system packaging and very low flow (suction) loss.

Things to keep in mind; No fittings in the suction routing when a bend could be used. No elevation changes from wing root to selector valve though I know that loss is recoverable. In the same mindset, pump inlet is same elevation as the fuel selector outlet. My later installation has the post filter mounted above the pump assembly. See post on the Aerolab review.

https://vansairforce.net/community/showthread.php?t=194876

Loose filter is the EFII pre-filter for comparison. That tunnel gets hot. If you stick with AvGas, should be no issues. MoGas will require some testing.

Your related electrical will require even more scrutiny, IMO.
Best of luck.

 

[Mark33]

Looks good!

I don’t see any reason your installation shouldn’t work in that location. I’m sure you already know, but pumps push a lot better than they pull. So, with that in mind, keep your pumps as low as possible and the distance between the tanks to the pumps as short as possible.

As a side note, I’d ditch those stock fuel filters and get some good Holly or other name brand filters…preferably ones that you can change or clean the elements. You can’t go wrong with 100 micron pre-pump and 10 micron post-pump filtration.

 

[spirit49]

Are planning on Avfuel only or going to burn car gas?

Planning a O320 with 160hp pistons, so I guess it will have to be AVGAS only.

I chose the Aerolab filter/gascolator for a couple of reasons; system packaging and very low flow (suction) loss.

How would that filter fare when installed underneath the fuel filter in that forward area.
Wouldnt exhaust gases/Heat be an issue?

No fittings in the suction routing when a bend could be used

I will train on bending and flaring the next weeks. Or in worst case using some hoses.

No elevation changes from wing root to selector valve

pump inlet is same elevation as the fuel selector outlet

So, with that in mind, keep your pumps as low as possible

Those requirements will be hard to deal with, since the fuel-selector would have to be mounted up high(unless I can make a selector arm extension).
Pump as low as possible and inlet at the same elevation as the selector outlet would also be a hard nut to solve.

But is it really so critical when the whole system is under pressure from double pumps?

 

[rocketman1988]

Planning a O320 with 160hp pistons, so I guess it will have to be AVGAS only.



How would that filter fare when installed underneath the fuel filter in that forward area.
Wouldnt exhaust gases/Heat be an issue?


I will train on bending and flaring the next weeks. Or in worst case using some hoses.





Those requirements will be hard to deal with, since the fuel-selector would have to be mounted up high(unless I can make a selector arm extension).
Pump as low as possible and inlet at the same elevation as the selector outlet would also be a hard nut to solve.

But is it really so critical when the whole system is under pressure from double pumps?

The EFII system never uses double pumps. Only one pump is on at any given time.

 

[rocketman1988]

Planning a O320 with 160hp pistons, so I guess it will have to be AVGAS only.



How would that filter fare when installed underneath the fuel filter in that forward area.
Wouldnt exhaust gases/Heat be an issue?


I will train on bending and flaring the next weeks. Or in worst case using some hoses.





Those requirements will be hard to deal with, since the fuel-selector would have to be mounted up high(unless I can make a selector arm extension).
Pump as low as possible and inlet at the same elevation as the selector outlet would also be a hard nut to solve.

But is it really so critical when the whole system is under pressure from double pumps?

The EFII system never uses two pumps at once. Only one pump is on at any given time.

 

[spirit49]

Thank you Bob.

The link to the aerolab was great.
Some great ideas to copy.

And Andair sell extension rebuild kits for their valves.

How important would you guys say it is to lower the valve down to the fuel tank inlet elevation?
I could use the lower part of the tank selector fot fuel in, and top for the return fuel. That would help a bit too

 

[Mark33]

Thank you Bob.

The link to the aerolab was great.
Some great ideas to copy.

And Andair sell extension rebuild kits for their valves.

How important would you guys say it is to lower the valve down to the fuel tank inlet elevation?
I could use the lower part of the tank selector fot fuel in, and top for the return fuel. That would help a bit too

To answer your question, it’s not really all that critical. The point is that you just want to use common sense and try to keep the pumps and selector valve as low as possible so that the pumps aren’t having to pull fuel uphill. I think your installation will work just fine. It’s not like there’s a huge difference in the fuel level and outlets of the tanks as compared to the pumps and selector valve.

The entire EFII setup is definitely auto fuel compatible….even with or without ethanol, and your 160 hp 320 will run just fine on it. If you’re ever concerned about vapor pressures, you can always add a few gallons of AvGas to the mix.

I do have a question about the gascolator. Is that one compatible with a high pressure fuel delivery system such as the EFII is? I’ve just never seen a gascolator being able to be used with a high pressure/constant flow fuel injection setup??

 

[rocketman1988]

Pumps

Pretty sure it isn’t going to make any difference what level you mount the pumps and selector. The standard pump is capable of 155 lph (about 41 gph) and it is running in a full return system; as soon as you turn the pump on, it will be cycling full flow through the fuel rail and back to the tank. A height difference of a few inches is not going to matter…

 

[Freemasm]

Some attempts at responses below.

How would that filter fare when installed underneath the fuel filter in that forward area. Wouldnt exhaust gases/Heat be an issue?

Yes/No. The exposure to the outside conditions is fairly limited. The surface area exposed to the tunnel conditions will be the main driver; so, any filter installed in that area will have almost identical responses.

And Andair sell extension rebuild kits for their valves.

Yes. I incorporated one though in line with the limited elevation change minimization. Probably not needed but as mine was a virgin lay-out, it made sense to me. This was when the future of AvGas had no options.

How important would you guys say it is to lower the valve down to the fuel tank inlet elevation?

You'll probably be fine. Elevation losses are recoverable, though will utilize more tubing. Result = probably an unmeasurable savings in suction loss savings. As mentioned, mine was a virgin layout/installation so why not? Minimize those bends and try to keep non-straight fittings at zero; not always possible.

I do have a question about the gascolator. Is that one compatible with a high pressure fuel delivery system such as the EFII is? I’ve just never seen a gascolator being able to be used with a high pressure/constant flow fuel injection setup??

It's on the suction side so it doesn't matter. As mentioned, it made my layout much easier, gave me an "inspectable" element, low pressure drop (attachment below), etc. Not saying I'm right. Just giving the OP more options to clutter his decision process; one of my superpowers.

Pretty sure it isn’t going to make any difference what level you mount the pumps and selector. The standard pump is capable of 155 lph (about 41 gph) and it is running in a full return system; as soon as you turn the pump on, it will be cycling full flow through the fuel rail and back to the tank. A height difference of a few inches is not going to matter…

Bob is a tech councilor for good reasons but I'm going to have to respectfully disagree here. A flooded pump suction is very important. While in theory, it would remain so under any conditions, operational reality says otherwise. An undetectable leak (or one that leak in vacuum versus pressure) can cause havoc. While the fuel pump will have some available "pick-up", it will be very limited; never seen this value listed by any pump OEM BTW. Moving non-compressibles (even momentarily) are way better at drawing a partial vacuum than trying to move air. Secondly, this type of pump has sliding contact. The pumped fuel is the only lubricant so don't let it run dry under any circumstances. MoGas (intended design application) typically has more lubricity than AvGas so it's even more critical. Besides, an engine stumble when switching pumps or changing tanks is never good for one's undergarment hygiene.

Other thoughts:

The Andair valve is a good choice in-line with the previous thinking. It is a three way isolation valve (blocks the unused ports) versus a ported ball valve. Can't practically have lower associated losses.

The EFII filters will work fine but have some limitations in my and others opinions. My pre is the Aerolab. My post filter will be replaced with an inspectable element type. Might want to look at this thread.

https://vansairforce.net/community/showthread.php?t=206413

Best of luck. Keep us informed. Stay warm in the CH winter.

 

[spirit49]

Freemasm

Thanks a lot to you and the rest.

Love these fast responses and great discussions.


I now finally have a warm shop to work on the -4, so I really hope that I can get some real momentum on my project.

I will return with some more pictures and questions as soon as I have digested all the info above.

Might even start a couple of other threads too, as I'm going through a lot of different tasks at the moment. Takes some time to get new bearings after not touching it for almost 2 years.

 

[rocketman1988]

To Note

I just spoke with TI Fluid Systems tech rep about the GSL393 155lph pumps that are standard for this system. I asked about this specific issue and what they considered acceptable.

The answer was that the pump should be gravity fed as much as possible, however, they say the pump can draw from a supply up to about a meter above the supply level.

They did not seem very concerned about a few inch difference in pump versus supply level, and went on to say that once primed, the internal check valve should hold the prime when power is removed.

Just thought you guys would like to know...

 

[Freemasm]

I just spoke with TI Fluid Systems tech rep about the GSL393 155lph pumps that are standard for this system. I asked about this specific issue and what they considered acceptable.

The answer was that the pump should be gravity fed as much as possible, however, they say the pump can draw from a supply up to about a meter above the supply level.

They did not seem very concerned about a few inch difference in pump versus supply level, and went on to say that once primed, the internal check valve should hold the prime when power is removed.

Just thought you guys would like to know...

Yes Sir and much thanks.

I am aware but also aware of the related reality. I've designed a lot of industrial turbine fluid systems; fuel gas, fuel oil, hyd, lube oil, etc. Been christened in the church of "Should Be versus Reality" a couple of times.

As mentioned, this type of pump (Positive Displacement) have some limited pick-up; self-priming to and extent. A meter of AvGas is just over a psi. That's not much and it's only talking head differential. Component losses like dirty filters or tank pick-ups can add to this. Likewise, fuel is the lubricant in this application and there is sliding contact in the parts. I can't quantify but a few seconds of dry induction is probably equal to a few hundred hours of nominal run time from a component life standpoint. Check valves are best suited for bulk application. They are notorious for poor sealing/internal leakage. Relying on them for tight shutoff is asking for issues.

For our applications, fault tolerance in the form of a flooded, cool pump suction due to elevation/location is an easy way to overcome sins like internal leakage, external leakage, etc. If not, more pump units would be "out of the way" on the hot side of the firewall, at some relatively high, convenient elevation. I personally can't think of any certified aircraft where the boost (in this case primary) is arranged such but there's always someone in EAB that has and will point to their "xxx hours with no problems" as validation.

Better to take advantage of the available physics here and steer as clear of fuel vapor pressure issues as much as possible. My two cents.

If anyone disagrees, Bob is right and I am wrong.

 

[rocketman1988]

Curious

Curious as to your thoughts on a pump location that provides a gravity fed supply while accounting for the duplex valve and dual pump manifold…you know, for my next build

 

[Freemasm]

The biggest design parameter us builders can influence is pump location. We can't influence tank pick-up location or more importantly a changing tank level. As mentioned, elevation delta P is recoverable so really it comes down to common sense. Limit fittings, bends, shortest run lengths possible, minimize elevation changes, chose components with good pressure drops and fault tolerance, e.g. excess filter area/higher flow rating, avoided the in-line pre-filter types as the available area would have created the need for related tubing gymnastics would not have been favorable, etc.

I'll admit may thinking was as conservative as possible. At that time, 100LL was being challenged through courts and political pressure and there was no approved alternative (yes I've been building and not flying that long). This made winter blend MoGas my system design point.

If I can stay alive long enough, I'm going to test the total pressure drop/pump inlet conditions of my system and simultaneously looking for vapor bubbles. My ultimate validation will be good pump suction side conditions with 1/2 the pre-filter element blocked, fuel at 140 degF and both pumps running. Wish me luck.

 

[rocketman1988]

Results

I’m wondering what you are putting in your tank that would block half of the filter!

Let us know what you find out…

 

[Mark33]

Don’t overthink it.

All I know is that I’ve had SDS/EFII systems in two airplanes and about to have the same in a third. I’ve always had the selector valve mounted in the stock location and mounted the pumps in the lowest location that was both feasible and convenient. I use 100 micron per and 10 micron post pump filters. I run auto fuel (both with and without ethanol) the mass majority of the time and I’ve never once had a suction pressure or vapor lock problem. I think that if anyone installing one of these systems just uses a little bit of common sense and doesn’t try to re-invent the wheel, their setup will perform as designed and run perfectly.

 

[Freemasm]

I’m wondering what you are putting in your tank that would block half of the filter!

Let us know what you find out…

Doing a system validation with new and clean elements is not the best application regarding fidelity with actual operating conditions. An elements job is get dirty. As it is arbitrary, what level of blockage would you recommend for a vapor pressure margin test?

Think DOD versus FOD. There have been cases where tank sealant, in varying quantities, has detached from tank surfaces. Some has been in sheets/pieces (common in certified world to glaze coat the skins inside of tanks) while others have come loose in small particulate form. A pre-filter is a single point failure so margin in the form of surface area/flow rating is good; specifically not talking element rating where finer can cause a different set of problems.

I have freely admitted that mine is a pretty conservative for the aforementioned reasons. The OP can weigh my comments and others and determine his path. I'm not sure why I have to keep justifying mine. I try my best to never make statements without providing technical reasoning.

It's not the alligators you see that get you.

 

[TS Flightlines]

Anything can be plumbed. As with all cases, there may be compromises needed to achieve that goal. The RV4 is tight, but it certainly can be, and has been done. Just think through all the components, and the limited space, and how each component operates.
I'd make a mockup on the bench of the areas in question and temporarily fit everything. Then tubes and hose can be fabricated. Sure beats crawling in and out of the plane, cutting, drilling, patching, starting over, etc. Then when youre satisfied with the setup, its a pretty straight forward process to transfer the components. As along as the mockup is accurate!

Tom