914 Low Power on Takeoff Attempt

I don't understand where the idea is coming from that the OP is having a drop in fuel pressure. There is no evidence to indicate that. What am I missing?

Look at the blue line in the top panel of each picture. In the "good" flight the fuel pressure remained stable at 4 psi or above. In the "bad" flight the fuel pressure (and airbox pressure) both drop suddenly, with the fuel pressure dropping to 3 psi.

in your checks I did not see where you removed and cleaned the individual pump screens.  Be careful as you cannot buy them as a seperate part.  

Cheers

earlier Kenz posted..

"What would be interesting to see is what happens as you pass the crossover point where airbox pressure is greater than atmospheric. "

The 914 is a turbo boosted engine and operates over atmospheric all the time in normal running.  100% power at 5500 is 33 inch HG and full power is 115 (limited to 5 mins) at about 40 inch HG for take off power.  

Should the airbox pressure ever exceed your fuel pressure then the balance will fail of pump pressure to boost...the float bowl will go empty and the engine will stumble or stop.  This is why it is important to run the pumps in series rather than parallel.  Volume is not the issue at take off it is pressure.  Without a differential gauge it is all a shot in the dark as the fuel pressure varies with manifold and is a constant moving target. UMA makes one just for the type 914.

Cheers

I think we'll get some useful info from my full power run tomorrow. I'll post the TCU and G3X-gathered data tomorrow afternoon.