Alan, I go along with that. My 914/twin Floscan set up has
worked nicely without any sort of jet. The only relevant
stipulation I can remember is that there should be a
reasonable length of fairly straight hose leading into
each Floscan as sharp corners will produce turbulence and
false readings. One of the key points with the Floscan I
believe is that even if its spinner jams it will not
significantly impede flow. It seems a bad idea to put
anything in the flow if you don't have to.
Regards, David Joyce, G-XSDJ
"rampil" <ira.rampil@gmail.com> wrote:
><ira.rampil@gmail.com>
>
> 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
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=408424#408424
>
>
>
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