Alan,
Floscan makes 3 models of the 201 sender for varying expected mean
flow rates of gasoline. The appropriate unit for the 914 is the 201A
model which handles 0.3 - 30 gal per hour.
If a jet is added, at least in my imagination of what a "jet" or orifice might
be, it will add turbulence and reduce accuracy of the flow turbine. I could
not find a reference to such an addition in the FloScan site. Further, in a
914 application, the meaningful flow regime is roughly 3 - 7 gal/hour, well
within the linear range of system. Does it really matter if the measured
flow rate at idle power (less than 2 gal/hr) is slightly off?
The only place where the flow rates are less than that is in the return line
to the tank. In my 912s application, the return flow is unmeasured, but
very small, since my measured forward flow rate are right at what Rotax
predicts in the manual. It is much less than the LAA posited rate of 0.8
gal/hr through the 0.35mm orifice.This was after I independently
calibrated my Floscan at three different flow rates. Perhaps the LAA
used a higher than Rotax max pressure head of 5 psi through the orifice?
The slight apparent increase in fuel flow rate (by not measuring the return
flow and subtracting it in the totalizer) seems to me a a safety feature.
BTW, any additional "jet" in the return line, if that is what you were
contemplating is a direct violation of the engine install instructions for the
914 which requires a low resistance path bach to the tank after the
pressure regulator.
The return flow rate situation with the 914 may be a bit different than
with the 912s, though the pressures and the return orifice are the same.
I recognize that if the LAA tells you that you must have return flow measured,
if measuring flow at all, you must comply.
It is just my opinion that trying to measure flow rates under 0.5 gal/hr will
be inherently inaccurate with the Floscan 201A in an aircraft environment
and isnot worth the trouble and expense. On the other hand, many
builders have this feature installed.
Best of luck!
--------
Ira N224XS
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