4) Air Pressure Hoses Q - Rotax 914 F Maintenance Manual

9.2.4)
00048
Date
Page
1997 02 01
36
Air pressure hoses Q
See Pic. 14.
The ROTAX 914 F is equipped with constant depression carburetors. For the
operation of the carburetors it is necessary that
a) the pressure in the float chamber corresponds with pressure at
carburetor air intake (airbox)
With varying airbox pressure (carb air intake) this changing pressure must
also act upon float chamber.
Therefore the float chamber venting is connected with the airbox.
b) the fuel pressure is approx. 0,25 bar (3.6 p.s.i.) above the pressure at
air intake (airbox).
Therefore the fuel pressure regulator is connected with the airbox.
Enrichening of the fuel air mixture at take-off performance
The airbox is furnished with 2 separately located pressure connections
interconnected by the 3-way solenoid valve W.
Up to the highest continuous power (approx. 1190 hPa airbox pressure) the
static airbox pressure prevails via the connection E on the float chamber of
the carburetor. At boost pressure (airbox pressure) above 1250 hPa the
pressure in the float chamber will be raised by the velocity pressure at airbox
(connection R) initiated by the TCU via the 3-way solenoid valve.
Thereby the effective pressure for the fuel dosing will be increased by the
same amount, too.
The aim of this mixture enrichment is to compensate the leaning down
process at higher atmospheric pressure by higher specific fuel consumption
and thus reducing thermal stress of engine and inducing better precaution
against knocking combusting during the short take-off phase.
WARNING: Since a failure of these pressure interconnections would
result in engine stop, ensure that these lines are in perfect
order, with tight clamps and without kinks.
1
1
Main
914 F
1
1
2
1
3
Reference
1
4
Modification no.
1
Pic. 14
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