The following block diagram shows the current (2005) layout for the fuel delivery system:
This is a picture of the current (2005) fuel pumps layout for inside the cabin:
The fuel leaves the valve and is pressurized by the pump in operation. Two throwaway filters are used and held in place with spring clamps. A filter change can be done in two minutes by placing a paper towel underneath them. If one filter is bad and the engine will run on the other and a filter change is due. Larger filters are planned for the production run.
This picture shows the current (2005) adjustable pressure regulator setup. The fuel comes in from A and goes out F. D is the regulator. The 2 extra clamps above the "B" are where the check valve is. Robert Paisley's testing has shown that the ECM can't handle the fuel mixture correctly at full boost, so it is controlled by adjusting the fuel pressure lower. E is the manifold pressure-compensating line. This assembly is mounted to the RT aft engine frame.
This is a closeup of the adjustable fuel pressure regulator. The barbed fitting has a hollow extension inside that pushes onto the internal diaphragm, thereby effecting a fuel pressure adjustment. When you are ready to set your fuel pressure you will loosen the brass nipple and screw it out until your pressure is what you want. Then use the locknut to lock everything in place.
The tasks outlined in this section can be accomplished prior to the arrival of your motor. The airframe must be outfitted with an additional fuel line for returning unused fuel to the tanks. Thus, each tank will have a supply, return, and vent line. An Andair six-port "duplex" selector valve is required. This valve is available from Eggenfellner Aircraft. The duplex valve assures that fuel is always supplied and returned to the selected tank. The Andair valve can be fitted into the existing valve location. The fuel lines must be bent in fairly tight radius to mate with the valve. The AN fittings must be threaded into the valve ports prior to installing the valve ports to the valve body with the supplied screws. Orient the fittings to allow the lines to mate with the fittings. Use an appropriate paste type thread sealant such as "Tightseal" available from Aircraft Spruce on NPT pipe thread fittings (use nothing under flared fittings or nuts). Avoid using Teflon thread tape. More than one accident (none involving our engine) has been related to small pieces of thread tape plugging up fuel systems. Flared fittings install dry with no sealant. Despite the instructions that come with your Andair valve, we suggest that you use blue LocTite thread locker rather than "spiking" the screws. This allows you to remove the fittings if you ever need to rework a line.
Supply Line: 3/8" tubing supplied with your kit.
Vent Line: 1/4" tubing supplied with your kit.
Return Line: 5/16" tubing you must purchase (12' - Aircraft Spruce p/n 03-39400)
NOTE: 5/16" tubing and AN #5 fittings are uncommon sizes in aircraft, but they are available from Wicks, Aircraft Spruce or other quality parts supplier. This size tubing is very common in automotive installations. Some builders have chosen to use 3/8" return lines with AN #6 fittings. This is acceptable, although routing and bending these larger tubes is more difficult. Note also that Eggenfellner Aircraft only stocks these valves with the 5/16" fittings. Beware of using common brass fittings. Brass fittings and cheap AN style fittings have a variety of internal diameters. Brass elbows in particular are notorious for being restrictive. Ideally, your fittings should be 0.19" or greater inside diameter as shown below (0.22"). It is acceptable to drill out fittings if you use care and common sense. It is even better to use the right fittings to begin with! Aircraft Spruce sells 3003-0 "Versatube". This is coiled aluminum tubing that is much easier to install than the 5052-0 rigid tubing, particularly if you need to make tight bends.
Refer to the parts list and drawings for a full list of required fittings and lines.
1. [ ] Note the starting time.
2. [ ] Install the 5/16" in-tank return line and fittings. An AN832-5D bulkhead fitting is used to connect the in-tank line to the tank end cover. Optionally, you may locate this fitting on the tank rib near the vent line fitting if desired. Be certain to avoid interference with fuel quantity senders and verify that the fitting will have room to mate to its counterpart on the side of the fuselage. Be aware of the location of the landing gear web and other fuselage fixtures before choosing your location. The specified location in the tank end lid is known to have ample clearance. On our factory RV-6A we were able to place the return fitting at the lower aft corner of the tank with a straight tube out into the second tank bay.
The in-tank segment of line is intended to return the fuel to a point just beyond the second rib of the tank. If you are using Vans capacitive fuel quantity senders, be sure to avoid contacting the capacitive plates with the return line. With float-type senders, bend the tube as needed to avoid interference with the float mechanism.
Fuel should be returned to a low point near the rear wall of the tank beyond the second tank rib. This assures that the warm fuel returning to the tanks will have a chance to mix with the cold fuel and disperse any bubbles. Keeping the return line below the level of the fuel in the tank will also help to prevent foaming.
By orienting the return tube near the rear wall of the tank, the tube will be unable to rotate and become loose. A small amount of ProSeal around the fitting nut will help to prevent tube rotation inside the tank. A snap bushing, drilled for 5/16" tubing, can be used in the second bay rib to prevent tube vibration. If you are using the capacitive fuel quantity senders you should never have a need to open the tank end plate again, so you might consider a dab of ProSeal rather than snap-bushings to prevent vibration. The same applies if you position the return fitting on the tank rib itself rather than the tank end plate.
Diagram of EFI Fuel Return System - Tank Fitting and Tube (492KB PDF File)
Photo of Tank Fitting and Tube with Float-Type senders.
3. [ ] Seal the tank cover plates with ProSeal and new cork gaskets. Van's catalog lists them if you need a new set. Note that many builders have reported leaks in their cork gaskets over the years. A general trend is to omit the gaskets entirely, in favor of straight ProSeal. This decision is yours to make.
4. [ ] Install the Andair (p/n FS-20-20-D2) six-port duplex fuel selector valve. Note that the three snap bushings are used for, top to bottom, the supply lines, return lines and brake lines. The tight radius bend at the valve can be made with a conventional hand tubing bender. A "Rigid Model 456" bender ($20 from Home Depot) was used for this installation.
To make the tight bends, thread the fuel lines in from the side of the fuselage toward the valve so that the tubing passes the valve by about 12". Next, insert the fitting nut and sleeve and make the end flare using a RoloFlare or similar 37-degree flaring tool. (BEWARE THAT MANY AUTOMOTIVE AND PLUMBING FLARING TOOLS ARE 45-DEGREE FLARES!). Once the flare is done, insert the tube into the bender as close to the end fitting as possible and make the bend in a single smooth motion. Don't hesitate to scrap a bend if it contains dents or other defects. Tubing is cheap. Just pull some more length through and try again until you get good bends. When all the lines are properly bent and tightened, you should be able to wiggle the valve body slightly to verify that no undue stresses exist in the line installation. It is important that the lines are not under mechanical stress, otherwise cracks and leaks can develop over time.
Be sure to clean each line with a blast of air to remove any metal filings.
Diagram of EFI Fuel System Components and Plumbing (718KB PDF File)
5. [ ] Install the supply and return lines between the selector valve and firewall. Recently, the factory has suggested that the fuel pumps be installed on the floor inside the center console rather than on the firewall. This places the pumps as low as possible for best priming, and keeps them out of the hot engine compartment. The electric pumps do create some noise, but once they are enclosed in the console, their sound will not be an issue.
Customization
The photo below shows one example of a cabin fuel system which places both pumps and a check valve in the center console. A homemade bracket mounts everything on rubber cushions to reduce vibration and noise. The finished cabin plumbing is protected with PVC wrapping and a custom fiberglass console and access lid (not shown). It is not necessary to do it this same way. Note in the photo that this builder has added a small screen-covered drain hole and air vent towards the rear of the console to allow fuel to drain away if a leak should ever occur.
6. [ ] Install the supply line to the bulkhead fitting on the firewall. The exact location of the supply line firewall fitting should be determined once the motor is mounted to the firewall and you have determined the location of the batteries and fuel pumps. The diagram provides a general guideline, but it is up to the builder to make the final decision as to its location.
7. [ ] Install the return line between the selector valve and bulkhead fitting. The diagram shows the desired location for this fitting in the upper right corner of the firewall.
8. [ ] Clamp all fuel lines as needed using Adel clamps.
10. [ ] The remaining fuel system connections on the engine side of the firewall, and all related wiring, will be described later.
11. [ ] Note the ending time.
