73-00-00
page 10
May 01/2007
Effectivity 914 Series
Edition 1 / Rev. 0
d02623
BRP-Rotax
Maintenance Manual
2.7) Pressure connecting lines (only on 914 Series)
See Fig. 73-5.
The engines of the 912/914 Series are equipped with constant depression
carburetors. For the operation of the carburetors it is necessary that
a) the atmospheric pressure in the float chamber corresponds with
atmospheric pressure at carburetor air intake (airbox)
With varying airbox pressure (carb air intake) this changing pressure must
also act upon the float chamber.
For this reason, the float chamber venting is connected to the airbox via a
pressure connecting line (1).
b) the fuel pressure is approx. 0.25 bar (3.6 p.s.i.) above the pressure at
air intake (airbox).
For this reason, the fuel pressure regulator (only on 914 Series) is connected
to the airbox via a pressure connecting line (1).
Enriching of the fuel air mixture at take-off performance
The airbox is furnished with 2 separately located pressure connections con-
nected with the 3-way solenoid valve (2) via pressure connecting lines (1).
Up to maximum continuous performance (approx. 1190 hPa airbox pressure),
the float chambers of the carburetors are vented with the static airbox pressure
via connection (3). At an airbox pressure above 1270 hPa, the pressure in the
float chambers will be raised by the ram air pressure at airbox (connection (4))
initiated by the TCU via an electric solenoid valve (2).
As a result, the effective pressure in the fuel bowl will be increased by the same
amount.
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