78-00-00
page 4
May 01/2007
Effectivity 912/914 Series
Edition 1 / Rev. 0
d02627
BRP-Rotax
Maintenance Manual
The turbine transforms the energy of the hot exhaust gases and drives
a blower which aspirates ambient air and transfers it precompressed
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 turbine impeller but not directly on engine speed.
â—† NOTE: Fig. 78 -1 shows a schematic arrangement of a boost
pressure control with the wastegate in the exhaust
stream
(1) engine
(2) exhaust turbocharger
(3) boost pressure regulating valve (wastegate)
Because of the large speed range of the engine and the varying power
requirement, control of the exhaust turbocharger is necessary to
achieve the respective nominal pressure in the airbox.
The waste gate directs part of the engine exhaust gases so that they
bypass the turbine and flow directly into the exhaust (by-pass).
â—† NOTE: With the wastegate completely open, the engine per-
formance can reach up to approx. 70 kW since not all
of the exhaust gases bypass the turbine.
00136
1
2
3
Fig. 78-1
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