I am about 99.9% sure that I have decided to put a rotary engine in my RV-8. I'm just now building the wings and I need to plumb in a fuel return line when I build the tanks. I've read that the fuel line needs to go to the highest point in the tank to prevent fuel from gravity feeding back durring shutdown. Any info on this problem or how you routed yours in the tank would be highly appreciated! Thanks!
Van's Air Force
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EFI Fuel Return Line Plumbing
- Thread starter copterdoc
- Start date
rodrv6
Well Known Member
I'm not sure why the fuel "running back" would be an issue. Especially if the induction system is above the level of the tanks. I'm putting an Eggenfellner Subaru in my RV-6, and his instructions for plumbing the return lines call for ending them in the tank at the bottom rear side in the second bay outboard. This allows the fuel to return under the fluid level in the tank and cuts down on foaming while allowing the warmer return fuel to mix with the cooler tank fuel before being picked up again by the pump.
I've got a Sube in my -6A. Used unibit to put extra return line holes in cover plate and Earls sealing washers on bulkhead AN fittings- no proseal needed, no leaks. I dump returned fuel into the top of the tanks to de-areate it.
No glitches to date. Think about your EFI fuel system carefully to avoid vapor lock and ensure feed to the high pressure pumps in all flight attitudes. Lots of people get this wrong and the engine becomes silent, bad news in an RV.
No glitches to date. Think about your EFI fuel system carefully to avoid vapor lock and ensure feed to the high pressure pumps in all flight attitudes. Lots of people get this wrong and the engine becomes silent, bad news in an RV.
Rotary10-RV
Well Known Member
rv8ch said:
Looks nice Mickey! Seems a nice workable solution.
Bill J
Rotary10-RV
Fuel return line
Thanks. The only thing I might change is to not use a 90 degree angled AN fitting, but a straight fitting. There is plenty of space between the wing and the fuselage (at least on the 8), so there is no reason to use a 90, and getting the wrench on is a bit easier with a straight fitting.Rotary10-RV said:
Thanks for the info guys! I'm just now building the wings but I like to plan ahead. I know I'll have a low & high press. pump for each fuel cell to the engine. These will be selected by a dual fuel selector with the return being routed back to the feeding tank. Now is there anything wrong with the standard fuel pickup position in the tank or any special baffling I should do inside the tank to ensure that the fuel doesn't run away from the pickup durring say a low fuel approach to landing? Pro's & con's on a gascolator for EFI? If anyone has a web site or knows some good ones for this type of info it will be greatly appreciated!
Fuel Systems for Homebuilt Airplanes
http://www.ellison-fluid-systems.com/article/fuelsystemsforhomebuilts/fuelsystems.htm
One of my favorite articles on homebuilt aircraft fuel systems is this one:copterdoc said:
http://www.ellison-fluid-systems.com/article/fuelsystemsforhomebuilts/fuelsystems.htm
copterdoc said:
Try these:
http://www.sdsefi.com/air27.htm
http://www.sdsefi.com/rv5.htm Has some photos of header tank, pumps etc.
I did not install and special baffling in tanks, not needed with a header tank. Gascolator is probably a laibility with EFI however many inspectors and regulations require one. I have a quick drain one on my header tank which satisfied the inspector here in Canada.
EFI Fuel filters
Ross, Your website is great. I really learn new stuff every time I visit. Is there an index of all your pages somewhere?
Quick question - did you install a filter between the header tank and the engine? If so, what kind?
Also, on your header tank system - do you just have the facet pump on all the time, and the "overflow" from the header tank goes back to the source wing tank?
What GPH rating do you run with your pumps?
Thanks!
Ross, Your website is great. I really learn new stuff every time I visit. Is there an index of all your pages somewhere?
Quick question - did you install a filter between the header tank and the engine? If so, what kind?
Also, on your header tank system - do you just have the facet pump on all the time, and the "overflow" from the header tank goes back to the source wing tank?
What GPH rating do you run with your pumps?
Thanks!
The main aircraft page is at: http://www.sdsefi.com/aircraft.html
Some of the RV specific stuff is on the -6A page at:
http://www.sdsefi.com/air9.html
I've started a page on the new RV10 project as well at:
http://www.sdsefi.com/air46.htm
Not much on here yet but I'll be detailing the Subaru EG33 conversion mods once the major airframe parts are done.
I have Earls mesh type filters between the low pressure pumps and the header tank and between the header tank outlet and the high pressure pump inlets, same type. These are about 4 X 1 inches, cylindrical.
One Facet and one high pressure pump must be on at all times while the engine is running. The Facets put out 30 gph at around 4-6 psi. Excess fuel is passed out the top of the header tank back through the Andair fuel selector to the selected tank. Excess fuel from the rail is also fed to the top of the header tank first before flowing back to the tanks.
The Bosch high pressure pumps have an internal check valve so either or both can be used. While some may consider this setup complicated, it does have full redundancy and is flight proven in bank angle up to 80 degrees, uncoordinated turns and extreme pitch maneuvers. Some of the other non- header systems I've seen give me the willies. Not sure if they will feed with low mounted fuel tanks with low fuel levels in uncoordinated turns.
Returned fuel always enters tanks at the top to allow entrained air or vapor to pass into the air and not be picked back up into the inlets. If you suck air or vapor with EFI on the high pressure pumps, the engine will stop right now!
Some of the RV specific stuff is on the -6A page at:
http://www.sdsefi.com/air9.html
I've started a page on the new RV10 project as well at:
http://www.sdsefi.com/air46.htm
Not much on here yet but I'll be detailing the Subaru EG33 conversion mods once the major airframe parts are done.
I have Earls mesh type filters between the low pressure pumps and the header tank and between the header tank outlet and the high pressure pump inlets, same type. These are about 4 X 1 inches, cylindrical.
One Facet and one high pressure pump must be on at all times while the engine is running. The Facets put out 30 gph at around 4-6 psi. Excess fuel is passed out the top of the header tank back through the Andair fuel selector to the selected tank. Excess fuel from the rail is also fed to the top of the header tank first before flowing back to the tanks.
The Bosch high pressure pumps have an internal check valve so either or both can be used. While some may consider this setup complicated, it does have full redundancy and is flight proven in bank angle up to 80 degrees, uncoordinated turns and extreme pitch maneuvers. Some of the other non- header systems I've seen give me the willies. Not sure if they will feed with low mounted fuel tanks with low fuel levels in uncoordinated turns.
Returned fuel always enters tanks at the top to allow entrained air or vapor to pass into the air and not be picked back up into the inlets. If you suck air or vapor with EFI on the high pressure pumps, the engine will stop right now!
Thanks everyone. It seems I'm on the right track. I was looking at tubing on Aircraft Spruces' web site. Are you guys using "Versatube" or one of the heat treated EXPENSIVE tubings? The Versatube has plenty of working pressure and will be my choice unless someone here knows better. I would think the harder tubes would be prone to cracking when bending or flaring. Which brings me to another question. Maybe this should be in the tools forum but which flaring and tubing benders have proven to be the best for us RVbuilders? Doug let me know if I'm taking this too far off subject and thanks for a Great web site.
