50
SSP 198/16
Sensors
The hot-film air mass meter
operates on the same principle as
before.
In certain engine operating states,
pulsations occur in the intake tract,
reversing the air flow - and this
gives rise to measurement errors.
The hot-film air mass meter is designed in such
a way that it is able to recognise this returning
air flow (pulsation fault).
This more exact method of intake air
measurement in all operating states improves
engine management and reduces exhaust
emissions.
The hot-film air mass meter is a thermal
flowmeter. A partial airflow from the
measuring pipe is fed past the sensor element
through a measuring channel in the air mass
meter housing.
The ascertained temperature values are
evaluated in the evaluation electronics. The
Motronic applies a voltage proportional to the
air mass to the air mass meter. This voltage is
needed to calculate the injection period and of
actual engine torque.
Substitute function and self-diagnosis:
The air mass meter detects air masses above
or below predefined limits. If the air mass
meter fails, the air mass is calculated on the
basis of a characteristic curve (throttle valve
angle and engine speed).
Hot-film air mass meter
Sensor element
Meas.
channel
Evaluation electronics
Hot-film air mass meter G70
Summary of Contents for 2.7-litre V6 Biturbo
Page 47: ...48 Notes ...
Page 71: ...72 Notes ...