is empty
Hi Ferg,
Serial or parallel or semi <grin> Anyhow in the setup as per old and new Europa
engine etc. one filter is connected to the reserve outlet and the other to the
main. That makes sense, because if one filter would block, you would be able
to select another way to go for the fuel. So up to here there is no difference
between series and parallel. To make things more complicated many others opted
to forget the filters and mesh on the tank-outlets and install one gascolator.
The filter element in there has a far larger capacity, and the particles
it let pass are smaller then the jets in the carbs.
Then the pumps, the new advice is to put them in series. That IS series, not
parallel.
But PARALLEL to the pumps are one way valves. Maybe this causes the
misunderstanding?
If one pump stops working and would pass fuel in the wrong direction
or not at all, the other one would all by itself, via the one-way valve
of the other pump, be able to supply all the fuel you would ever need. Without
the check valves on the parallel system, there is a situation possible where
the fuel from one pump would return through a defect other one. With parallel
pumps and the check valves in series with the pumps, that problem does not
exist. I just do not like to swirl that will happen with a double, never needed
flow.
Fuel pressure with both pumps running in series is double of the parallel
system.
Similar to the electrical analog. Fuel flow is double of the serial
configuration.
Both, pressure and quantity is more then your engine can ever eat. Fuel
pressure in the crab bowls is regulated by: a regulator, which on the 914 gets
it's information from the air-box pressure. Fuel return flow is just a factor
of the quantity, somewhere i seem to remember it to be 40 to 45 liters with
one pump on.
Since i will be monitoring fuel flow, there will be one sensor for forward and
one for backward flowing fuel. There will be a press and hold contact to block
the pulses from the back flow sensor. In my run-up checks i will press that
button,
and check that i have +40 liter flow while switching from one pump off
and other on.
Hope it helps,
Jos Okhuijsen
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