914 Fuel Pressure/Prop Pitch

by Dave St.Clair in 912 / 914 Technical Questions one month ago

I changed the my prop pitch on my 914 by a couple degrees and I’m getting 5100 rpm on the takeoff roll and easily 5500 rpm at cruise. Engine temps are fine. Climb is 1000fpm+, cruise is upwards of 130 KTAS at 8K. All good — except my fuel pressure is in the yellow (defined in my Sting S4’s G3X as 10.9 to 12.0).

I believe the 914 has a pressure regulator to ensure the carbs get a constant 3.6 psi or so. Right?

So isn’t the absolute fuel PSI somewhat meaningless? Or do I need to adjust the pressure and, if so, how?

Re: 914 Fuel Pressure/Prop Pitch

by Dave St.Clair » one month ago

Dave St.Clair

2 6 16

Well, my fuel pressure sensor is a Kalvico P4055-50G so it measures ‘gauge’ pressure relative to atmospheric versus a differential, which is what it should be. Other than lower pressure below 2.2 psi, the reading pretty much has no value. I have a fuel flow sensor (red cube) so that’ll do for now for monitoring the fuel system until I get around to putting in a differential sensor.

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Re: 914 Fuel Pressure/Prop Pitch

by Rotax Wizard » one month ago

Rotax Wizard

2 1.01k 4.35k

fuel pressure in any turbo engine, 914 included, is a delta between the airbox and the fuel pressure. It is not something that is given as atmospheric as the 914 runs boosted and not turbo normalized. 39 to 40 HG on take off and about 33 HG at max continuous. The chart is in the operator's manual.

Cheers

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914 Fuel Pressure/Prop Pitch

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