Fuel pressure drop

Hi again,

"The EI FT-60 "red cube" fuel flow transducer operates using an optical sensor which senses when the light from an internal LED is interrupted by the rotor passing between the LED and the sensor. Bubbles in the fuel can interrupt (refract) the light from the LED, which the sensor cannot differentiate from interruptions caused by the rotor. Either event will cause the transducer to send a pulse to the EMS. Additionally, because vaporisation (what you've called cavitation) increases the volume of the fuel itself, the rotor would also spin faster for the same mass of fuel passing through.
Therefore when fuel vaporisation is present the fuel flow transducer will erroneously present a higher fuel flow measurement to the EMS. This can apply to either or both transducers, but probably not in such a way that the error in one exactly cancels out the error in the other."

Interesting.

My two Red Cubes are positiond on the:

# main fuel supply line, between the mechanical pump & before the distribution block/manifold.

# return to tank line.

The return to tank line's primary purpose is to "draw off" fuel vapour before it gets to the carburettors ie it can be expected to have fuel vapour passing through it.

The return line Cube is supposed to allow subtraction of return fuel flow to the tank, from the delivery line Cubes sensing, thus giving an instant fuel flow/used reading and a total fuel used/remain reading. 

From your description of the Red Cube function (bubbles causing optical interruption/false reading) should I consider removing this sensor as a possible source of /contributor to, my erroneous fuel pressure/flow readings?

I know , from experince, that a single fuel flow sensor (Cube) can be calibrate to deliver a perfectly adequate fuel flow/used signal.😈