6 Series 650i (N62TU) Coupe
The formation of hydrocarbons in the fuel tank is dependent on:
•
Fuel temperature and ambient temperature
•
Air pressure
•
Fill level in the fuel tank
In a current-free state, the fuel evaporation control valve is closed. This prevents the ingress of fuel vapour from
the activated carbon filter into the inlet pipe when the engine is switched off.
Closed-loop Lambda control system
Optimum efficiency of the catalytic converter can only be achieved if an ideal fuel/air ratio is used for combustion
(
λ
= 1). To this end, oxygen sensors are used upstream and downstream of the catalytic converter.
The oxygen sensors upstream of the catalytic converter have a steady characteristic output curve (measure
oxygen content in rich and lean ranges.)
The measurement method employed by this oxygen sensor is different to an oxygen sensor with an erratic
characteristic output curve. The oxygen sensor is therefore connected using 6 pins instead of 4.
•
Oxygen sensors upstream of catalytic converter
The oxygen sensors upstream of the catalytic converter (control sensors) are used to assess the
composition of the exhaust gas.
The control sensors are screwed into the exhaust manifold.
The oxygen sensors measure the residual oxygen content in the exhaust fumes. The voltage values
determined are relayed to the DME control unit. The DME control unit corrects the mixture composition by
adjusting the injection period.
Values which are greater or less than
λ
= 1 are aimed at depending on the operating condition.
•
Oxygen sensors downstream of catalytic converter
The oxygen sensors downstream of the catalytic converter (monitoring sensors) are used to monitor the
control sensors. In addition to this, the function of the catalytic converter is monitored.
To ensure full operational reliability of the oxygen sensors upstream of the catalytic converter, a temperature of
approximately 750
°
C is required (350
°
C for oxygen sensors downstream of the catalytic converter). For this
reason, all oxygen sensors are heated.
The oxygen sensor heating is controlled by the DME control unit. When the engine is cold, the oxygen sensor
heating remains switched off, as condensation which is present would otherwise destroy a hot oxygen sensor
due to thermal strain.
This means that the closed-loop Lambda control only becomes active a short time after the engine has started,
once the catalytic converters have warmed up. The oxygen sensor is initially warmed up using a reduced heating
power, to avoid imposing unnecessary loads on it due to thermal strain.
Torque monitoring
The DME monitors the torque required.
The following systems may request torque data from the DME control unit:
•
Active Steering
•
Servotronic
•
Alternator
•
Cruise control
•
Dynamic Stability Control
SBT 8-cylinder spark-ignition engine N62TU E60, E61, E63, E64, E65, E66, E70
BMW AG - TIS
19.01.2013 07:33
Issue status (12/2007) Valid only until next DVD is issued
Copyright
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