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MikeEasley wrote: is the aneroid bellows that's been
discussed the
feature of the fuel pump that richens the mixture at full
throttle?
The metering unit is a
big player but here is what the aneroid does. The aneroid housing is
referenced to deck pressure. The aneroid bellows expand when the air
pressure surrounding it decreases. As the aneroid expands it moves the rod
increasing the size of the orifice opening. An increased amount of fuel
flows through the orifice to a recirculation path. This
decreases fuel flow from the pump to the fuel metering unit. So as
boost increases, fuel flow to the engine increases and boost decreases, fuel
flow decreases due to the aneroid.
The fuel system on the TSIO550 is
designed to allow high boost from an auxiliary pump to be used as a back up
for engine pump failure. There is a check valve in the system for this
purpose.
Craig
Berland
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