I spoke to one of the fuel computer manufacturers about this problem.
They are looking at a solution but nothing is coming yet. The real
problem is the fuel return flow. I think all of the less expensive flow
meters use impeller or vane type senders which generate frequency/flow
signals. The problem is these devices only operate over reletivley small
ranges. I have several senders here which work well on Rotax engines.
Typically they measure a 10 l/hr or 25 l/hr with very acceptable errors.
The trouble is to have a sensor which measures a high volume you must
have a large jet over the vane or impeller. The same sensor will not
generate enough fluid velocity when the flow rates are low to spin the
impeller.
For eample a normal 912 impeller works well above 6 litres per hour but
it may stall at a little less than this flow rate say 4 l/hr. maximum
flow is 23 l/hr giving a range of less than 6:1.
For the flow return flow rates can be higher than 20 l/hr down to
nothing.
Volumetric or displacment meters may be the only solution but they are
expensive and I have no experiance with these devices.
Jerry
lts@avnet.co.uk
http://www.avnet.co.uk/touchdown
Subject: Fuel Flow guage
Could anyone out there advise me of a reasonably priced fuel flow
guage ? the cheaper one sold by RD has a 1/8th Inch orifice in the
transducer which I understand gives flow problem from time to time -
their expensive one is very expensive as with a 914 you need and extra
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