Flygas mechanical fuel pump for the 914?

Joe

the servo motor on the type 914 will lock in position if the power is lost.  

If this happens and you are in full boost, it would have to occur in take off configuration, then your only option would be to throttle down to reduce power.  The normal process is to do as Ken suggests.  One pump powered from the generator side of the engine and one off the power buss (battery side)  If you lose engine power generation you would need a battery that will keep the other pump working for at least 30 mins is the normal recommendation.  (45 mins if you are IFR authorized according to the FAA) 

Cheers

Joe Asked;

" ...This is advertised as a mechanical fuel pump for the 914. How is this possible? I thought that the 914 needed an electric fuel pump because the mechanical ones do not produce enough pressure. Does this pump produce enough pressure to work on the 914? It claims a minimum of 0.4 bar even at the lowest RPM and a maximum of 3 at the highest. But isn't 0.4 too little for airbox pressure + 0.25 bar?  ..."

You are misreading the specs.
This pump is most likely a Gerotor Style Pump.
It is capable of 14 bar Max.
The Pressure Regulator on the engine determines whether you will see 0.4. 1.0 or 3.0 bar.

The spec chart is NOT detailing the PRESSURE at various Specified RPMs.
It is showing the Flow VOLUME at various Specified Pressures and RPMs.

Even so,  0.4 bar (Gauge) would still be way more than the needs of the typical airbox with a pressure of 15"Hg (Abs)  (-0.5 bar Gauge) at idle.

The pressure does not need to exceed 0.4 bar (gauge) until the Airbox exceeds 1.15 bar (~34"Hg)
It only needs to reach ~0.68 bar at 40"hg.
Hence, a 1 bar pump has plenty of reserve capacity in this installation.

Thank you! So the regulator restricts flow until pressure builds up enough and all a pump has to do is handle that pressure and maintain enough fuel flow?

Joe wrote:

Thank you! So the regulator restricts flow until pressure builds up enough and all a pump has to do is handle that pressure and maintain enough fuel flow?

That pretty much sums it up.
The Pump is directly coupled to the crankshaft, so it runs at engine speeds.

Idle to WOT, the flow varies from 45 to 162 L/Hr.  (~10-40 Gal/Hr)
Way more than the engine will ever need.
40 gal is probably more than a full tank of gas so it sounds like a firehose.
But don't forget that it takes an HOUR to move that much fuel.
Do the math and you will find that is about an Ounce (~25cc) per second.  A slow faucet!
Not so impressive, but way more than required.

At idle the engine uses about a half-gallon per hour.
The pump is delivering 10 gallons, so the regulator returns the other 9.5 gallons back to the fuel tank to be used again.