Rotax 915 i A series Maintenance Manual page 462

SYSTEM DESCRIPTION
ROTAX® engines of the 915 i A Series are equipped
with an exhaust turbocharger which makes use of
the energy in the exhaust gas for pre-compression of
the intake air. The exhaust collects all gases which
accumulate in the combustion chamber of the cylin-
ders and routes them via exhaust bends and exhaust
manifold to the exhaust turbocharger. There, the
combustion gases drive the exhaust gas turbine to
achieve a power increase. From the exhaust turbo-
charger, the combustion gases are routed to the muf-
fler, which is fitted for noise reduction.
The airbox pressure is controlled by a flap (waste-
gate) at the exhaust gas turbine, which is driven by a
pressurized regulator. The operation of the flap
works via a linkage of the pressurized regulator.
Exhaust turbocharger
The exhaust turbocharger is basically an arrange-
ment of two fans, a turbine and a blower, on a com-
mon shaft. The turbine transforms the energy of the
hot exhaust gases and drives a blower which aspi-
rates ambient air and transfers it pre-compressed via
the carburetors into the cylinders.
The sole operational connection between engine and
turbo is the air and exhaust stream. The speed of the
turbo depends mainly on the pressure ratio at the tur-
bine impeller but not directly on engine speed.
Figure 21.3: Schematic of a boost pressure
Engine
1
Boost pressure regu-
lating valve –
3
wastegate
78–20–00
Page 4
August 01 2018
BRP-Rotax
MAINTENANCE MANUAL HEAVY
Exhaust turbocharger
2
NOTE
The figure shows a schematic arrangement of a
boost pressure control with the wastegate in the
exhaust stream
Because of the large speed range of the engine and
the varying power requirement, control of the ex-
haust turbocharger is necessary to achieve the re-
spective nominal pressure in the airbox.
The wastegate directs part of the engine exhaust
gases so that they bypass the turbine and flow di-
rectly into the exhaust (by-pass).
MAINTENANCE
As well as the maintenance and special
checks, see Maintenance Manual Line for
the engine type 915 i A Series915 i B
Series.
CONNECTIONS FOR DISPLAY SYSTEMS
ATTENTION
Follow the instructions in the installation man-
ual regarding connections for instrumentation.
Effectivity: 915 i A Series
Edition 0/Rev. 0