In message <f.8a3a132.26dcac58@aol.com>, Grahamclk@aol.com writes
>In a message dated 27/08/00 23:18:03 GMT Daylight Time,
>grasingleton@avnet.co.uk writes:
>
>IMHO air problems due to vapour lock, bubbles and even leaks would disappear
>if the tank were not vented to air, but maintained at positive pressure
>(regulated electric air pump ?) instead. The original forward facing vent
>followed this theme, but was later negated by the addition of the water exit
>hole.
>
I don't think this would be a long term solution. The pumping of
volatile hydrocarbons is a classic problem in the chemical industry. The
answer is that there is no substitute for liquid head. Pressurising with
nitrogen or any other gas leads to bubbles of nitrogen etc. The only
other solution is a submersible or centrifugal pump at the low point of
the system. In the short term pressurising with a gas overcomes the
cavitation problem, but that is because the liquid reaching the pump is
not yet saturated with gas. In our case the electric fuel pump should be
at the lowest practicable position and the filter should be no finer
than specified by the pump manufacturer. Filtration for the benefit of
the carburettors could be carried out after the Rotax mechanical pump.
Ken Whiteley
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