My Fokker DVII Project

[j ferguson]

Originally Posted by Bookmaker

I would assume that the throttle body injection setup would run on higher pressure than a carb system as well. Possibly requiring a return line to the fuel tank.

That brings up a question as to if there is a metering system in the return to keep the pressure up rather than just sending all the fuel back to the tank. If so, how is it set up?

Dale

Hi Dale and Jeff,
Ellison's web site shows a very simple system with gravity flow from the tank to a boost pump, gascolator, engine driven pump (looks from their drawing a diaphragm pump - which can be pumped through) to a line running to the carb with a bleeder back to the tank. the bleeder has an orifice which Ellison says - correctly- needs to be sized small enough to maintain back pressure so that the carb gets the fuel flow it needs at all power settings.

Bleeder is to have someplace for the inevitable bubbles to go - back to tank.

Jeff, are you sure you can't pump through the pesco when it isn't running?

hopefully helpful, John

[tengew]

that would be easy to set up and do a test run on jeff
did you post pics of the pump your using ? is it two gears that mesh pumping the gas ?

[j ferguson]

Originally Posted by tengew

that would be easy to set up and do a test run on jeff
did you post pics of the pump your using ? is it two gears that mesh pumping the gas ?

From his earlier pictures of it when he got it, it's a vane pump, just the thing for gasoline, which appears to have a built-in pressure relief valve which looks like it would work the same way as the integral pressure relief valves on automobile oil pumps - namely when the back pressure on the discharge side gets up to the relief setting, the valve short-circuits the discharge side to the inlet side and the pressure can't get any higher.

It could be that the body of the pump is configured to bypass the vanes if you push fuel through from the inlet side as you would with a boost pump.

[Jeff Brooks]

The Ellison EFS-4-5 Throttle only requires between 2 - 6 psi fuel pressure.

The Pesco 2P-227-D engine driven fuel pump installed on my Ranger is a low pressure pump. It puts out 2.8 psi @500rpm, and 4.0 psi @ 1000rpm. the max output is somewhere around 6.5 psi. I did find that there is a bypass through the pump should the pump fail.

However, in the article provided on the same webpage, they suggest that routing the fuel in series through the fuel pump is not advisable as the pump creates a lot of heat, (especially if it has ground it's self up before failure) which creates the vapor lock. The article I am talking about is: "Fuel Systems for Homebuilt Airplanes by Lyle S. Powell, Jr." is on the same Ellison webpage where you saw the fuel system diagram you mentioned. The article advised to run the boost pump & mechanical pump in parallel, with a check valve ... even though the diagram shows otherwise.

The electric pump I am using is the Facet Electric Fuel pump (Solid State) Model No 40108, in the Aircraft spruce catalog (page 258). This pump produces 4-6 psi. This pump also has a built in pressure relief to prevent flooding.

Initially, I was going to put a Holley Bypass regulator near the carb with a fuel return line to the main tank, but when I asked both the manufacture of the relief valve & Joe Denest (one of my Ranger experts) they both said I don't need it with this pump setup.

P.S. I'm digging all this input! I want to make sure I haven't left any stone unturned!

[j ferguson]

Hi Jeff,
I'm pretty certain all the pump-through mechanical pumps I have any experience with were diaphragm pumps not vane pumps. the idea of pumping your fuel through a vane pump that was busy eating itself is not so good and I tend to agree that you would want your backup system to be able to get fuel to the carb without it getting near the mechanical pump. simple way to do this is connect discharge from boost pump closer to carb and put a checkvalve in line coming from mechanical pump which is what I think you wre planning on.

You will have an advantage in flight that some of us who've only flown store-bought planes don't have. You will really know and understand the system.

best regards, John

[US95Damiani]

Jeff,

Ok in my research, the pesco vane pump as you stated, has a bypass for just such an emergency as pump failure. All of the aviation engine driven pumps are equipped as such.

On Lycoming AN type pump installations usually brand names are Lear Romec or Kelly Systems (AN = Vane type) which are typically used in High Heat installations such as a Turbocharged engine (A Lycoming TIO-540-AE2A comes to mind)
Specifically, Piper uses an electric pump plumbed through the AN type engine driven pump in series. the electric pump relies on engine pump relief valve for pressure regulation. Then of course the electric pump also has to pump through the "failsafe" bypass on the engine driven pump in the event of failure.

On the GAAM Great Lakes we also run a pesco type vane type pump which is able to put out 16 PSI for the pressure carb. we run an electric pump in series into the engine driven pump. ala the Piper style system
It works well and has been proven through 50 years of operation in many different type airplanes.

On another note regarding the fuel return I was not able to get a diagram, of the fuel return system but I was able to verify that on a Bendix PS-5 setup or on a Bendix RSA injection system the excess fuel bleed is ported directly back to the fuel tank. or header tank whichever the case may be.

I hope this helps and makes sense!

[Bookmaker]

Jeff, looks like you're getting some good info on fuel systems.

One other note that I will pass along based on a recent article in the AOPA magazine. Be sure to set up the system, or at least an appropriate checklist so as to prevent the possibility of pumping fuel from one tank into the other possibly causing it to overflow.

It looks like the valve system you have would prevent this, but if you add a return line to one of the tanks, the possibility may open up.

Dale

[Jeff Brooks]

Hi all,

It has been a while, but life has been busy for me lately!
I received my oil tank from Pavel Novak recently.



I took a break from the ribs to make clamps to mount it to the plane (something new to work on!). I looked at Pavel's method, but decided to stay away from welding the mounts directly to the frame. I want to keep it original in case a Merc IIIa or BMW falls in my lap!

Here are a few pictures of the clamp. Yes, I know my welding ain't pretty!



Right now they are just there to test the fitting of the pieces. Later, I will remove them, sandblast it, prime & paint it. Then add a cork lining inside the strap to separate the dissimilar metals.

[Jeff Brooks]

You can see how much room there is underneath the tank for the fixtures & drain valve.


Here is how I added a tube to mount the clamp without welding it to the frame.


The filler neck lines up nicely where the access door that goes on the original panel ... stroke of luck there!


Pavel mentioned that if the oil pump ends up higher than the oil level in the tank, I may need to add a one way check valve to the pressure pump line to keep the line from draining and causeing the pump to cavitate. Here you can see the pump is at least at the return opening ... and this is with the plane leaning back in the landing configuration.

[Jeff Brooks]

Hi All,
I have been working on hanging the oil cooler to complete the oil system. Again, I did not weld directly to the frame as I am now able move the parts around to make adjustments.
I couldn't decide where to put the oil cooler for a while, as there really isn't a neat place for it. So, I decided to put it directly under the engine.


I welded an ear onto the ends of a piece of tubing and bought those Fokker style clamps from Wicks. Then I spaned the bottom tubes on the bottom of the frame.


I added hard points to both the front & back of the clamps on the cooler and again used the Fokker style clamp.