Mercedes-Benz OM 471 Introduction Into Service Manual page 52

The injection quantity is also dependent on the following input
parameters:
f Engine speed
f Air mass
f Coolant temperature
f Fuel temperature
The altitude correction and smoke emission limitation can also
influence the injection quantity (actuation period) as well as the
start of actuation of the fuel injectors.
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If the specified engine torque is negative, e.g. in deceleration
mode, and if the motor speed lies above 950 rpm, the engine
management (MCM) control unit (A4) interrupts actuation of the
fuel injectors for cylinders 1 to 6 ( Y608 to Y613) and lowers the
fuel pressure in the rail via the rail quantity control valve (Y642).
In this way the braking effect of the engine is used and the fuel
consumption lowered.
The engine brake can be activated to reinforce the braking effect.
The driver can select between 3 brake stages.
If the motor speed drops below 950 rpm, the engine management
(MCM) control unit (A4) increases the fuel pressure in the rail over
the rail quantity control valve (Y642) and actuates the fuel
injectors for cylinders 1 to 6 (Y608 to Y613).
Determination of the engine speed and
crankshaft angle, function
Determination of the compression stroke
at cylinder 1, function
Determination of the coolant temperature,
function
Determination of air mass, function
Determination of the fuel temperature,
function
Function of the specified engine torque
calculation
Fuel supply, function
Exhaust gas recirculation, function
Forced induction, function
Engine brake, function
Exhaust aftertreatment, function
i Introduction of engine OM 471 and exhaust aftertreatment > 09/2011 >
– This printout will not be recorded by the update service. Status: 09 / 2011 –
Altitude correction
The altitude correction is primarily designed in such a way that the
turbine speed, the compressor outlet temperature and the
turbine inlet temperature of the turbocharger, as well as the
air/fuel ratio n (Lambda) does not exceed or drop below
established limits. To do this, the exhaust gas recirculation rate
(AGR rate), the actuation begin as well as the actuation period
(injection quantity) for fuel injectors for cylinder 1 to 6 (Y608 to
Y613) are adapted.
Smoke limitation
The fuel quantity is limited via the smoke limitation characteristics
so that virtually no output of smoke occurs.
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The exhaust gas recirculation (AGR) is active throughout the
whole driving mode to reduce the nitrous oxide emissions.
In the case of the exhaust gas recirculation (AGR), the suctioned
out or supercharged fresh air is mixed with exhaust gas. This leads
to the situation where the oxygen content of the suctioned out or
supercharged air drops and its specific heat increases.
One can therefore achieve a lower combustion temperature and
thus reduced output of nitrogen oxides (NO
increases with increasing combustion temperatures. The amount
of exhaust gases produced is also reduced.
Vehicles with code (M5R) Engine version
EEV and vehicles with code (M5Y) Engine
version Euro V
Vehicles with code (M5Z) Engine version
Euro VI
Functions
), whose proportion
x
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