Forwarded from bounce bin. Message is from
Klaus Dietrich <Klaus.Dietrich@oracle.com>
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It seems that I fixed the problem by eliminating the fuel flow sensor which was
mounted after the return line just before the distribution tee to the
carburators.
I also have a shut-off valve for the return line accessible in the tunnel next
to the fuel selector. Seems that this cured the low fuel pressure; I'm not sure
but the cooler outside temperatures we have now (below 20C) may also contribute
to a better fuel pressure and less "bubbles". In future, and at OAT of over 25C
on the ground I will also mix 50% Avgas to my unleaded auto fuel to further
prevent vapor lock. (If you're planning to do this you should use semi-synthetic
oil or mineral oil; we had good experience over the last three years with
Castrol GPS motorcycle oil)
Klaus
ami mcfadyean wrote:
> Dave,
> I think you missed my point. The flows measured were under gravity from a
> point just downstream of the fuel valve (the fuel line was disconnected at
> that point and a calibrated container put in place to catch the flow). This
> was WITHOUT any contribution from any pump. Downstream head losses in the
> remainder of the complete system would confirm that the engine pump is
> having to suck (ie put much of the fuel line at less than atmospheric
> pressure ) to draw along the fuel; This would increase the risk of vapour
> formation.
>
> It would reinforce the need to install the auxiliary pump as low as possible
> and with as few flow restrictions as possible between it and the tank. Some
> types of pump (eg roller cell) aren`t good at sucking and, if they become
> unprimed (eg by vapour locks), aren`t good at getting things going again.
>
> Duncan
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