Intake air temperature pressure sensor

The intake air temperature pressure sensor is attached to the charge air pipe.

This combined sensor delivers the following information to the Digital Motor Electronics (DME):

• Temperature of the charge air
• Charging pressure.

The purpose of the charging pressure sensor is charging pressure control. The Digital Motor Electronics (DME) also adjusts the position of the throttle valve based on the signal from the intake-manifold pressure sensor.

Intake-air temperature sensor 

A temperature-dependent electrical resistor is used for temperature sensing. The circuit contains a voltage divider where the resistance can be measured depending on the temperature. A temperature is converted using a characteristic curve specific to the sensor. An NTC resistor is installed in the intake air temperature sensor; its resistance value falls as the temperature rises. The change in resistance between 167 kΩ to 150 Ω is temperature-dependent, and corresponds to temperatures between -40 ° C and 130 °C.

Boost pressure sensor 

Strain gauges are used to record the charging pressure. A membrane equipped with strain-gauge strips is deflected by the applied pressure. The changes in resistance in the strain gauge are electronically detected by a Wheatstone bridge and evaluated. The voltage measurement is then used as the actual charge-air-pressure control value.

Fig 1: Intake-Air Temperature Sensor

Courtesy of BMW OF NORTH AMERICA, INC.

The charging pressure information is sent to the Digital Motor Electronics (DME) via a signal line. The signal for evaluation of the charging pressure fluctuates depending on the pressure. The measuring range of approx. 0.5 to 4.5 volts corresponds to a charging pressure of between 20 kPa (0.2 bar) and 250 kPa (2.5 bar).

Fig 2: Intake-Air Pressure Sensor Graph

Courtesy of BMW OF NORTH AMERICA, INC.