Location
The mass air flow sensor (B642) is located on the charge air pipe downstream of the charge air cooler on the left engine side.
B642 | Mass air flow sensor |
W07.07-0001-06
Task
The mass air flow sensor (B642) detects the air volume led to the engine. At the same time it measures the current pressure and the temperature of the supercharged air.
Function
The mass air flow sensor (B642) is fitted with a pressure differential, absolute pressure and temperature sensors. A powerful microprocessor prepares the respective sensor signals, filters and calculates these and communicates via the engine-CAN (CAN 16) with the engine management (NGT) control unit (A4d).
The mass air flow sensor (B642) detects the pressure, the temperature and the flow of the supercharged air (from the pressure differential over a Venturi measuring pipe) up to 4000 times per second and analyses the measurement results.
The mass air flow sensor (B642) offers the following advantages compared to conventional mass air flow sensors:
High precision for measurement of pulsating air masses
Compact component dimensions
Rapid adaptability to new common Xentry functions
Calibrated sensors
No inaccuracies of measurement due to soiling such an oil film or condensation
High idle times
The mass air flow sensor (B642) is supplied by the engine management control unit (NGT) (A4d) with a 5 V direct voltage.