Description of engine OM 607
50
Drive
b
Introduction of the New A-Class, Model Series 176
Boost pressure control
The boost pressure positioner is actuated for boost
pressure control by the CDI control unit using a
pulse width modulated signal (5 to 95%). This then
continuously actuates the vacuum unit for boost
pressure control with vacuum to match the duty
cycle.
The adjustable guide vanes alter the flow cross-
sectional area through which the exhaust flows
onto the turbine. They adapt the gas pressure
applied to the turbine to match the required boost
pressure. The speed of the turbocharger deter-
mines the volume of pre-compressed air and there-
fore the boost pressure.
To act as protection against any thermal and
mechanical overloading of the turbocharger, the
exhaust temperature is monitored by the CDI
control unit using the temperature sensor upstream
of the turbocharger and the exhaust back pressure
by the exhaust back pressure sensor. If a possible
thermal or mechanical overload is recognized, the
boost pressure is reduced.
i
Note
A bypass bore (0.24 mm) ensures that there is a
constant opening in the ventilation (atmosphere)
to the control pressure. This is why it is not
possible to define a leak test for the boost pres-
sure positioner. The boost pressure positioner
function may be impaired by soiling of the inte-
grated filter.
P07.16-3812-00
Y77/1 Boost pressure positioner
– This printout will not be recorded by the update service. Status: 06 / 2012 –
