Airflow Sensors

Another problem facing automotive engineers was, how to monitor the volume, density, and temperature of the air entering the engine. The ECM needs this information in order to calculate the correct air fuel mixture. Vane air meters and mass air flow sensors have been designed to handle this job. They are located in the air duct or intake manifold, so that all the air entering the engine has to pass through the device.

Vane Air Meter

The vane air meter was the first design used to monitor air flow. Vane meters are a combination mechanical and electrical device. As the air is pulled into the engine it must flow over a vane door. The movement of this door causes a potentiometer to modify an electrical signal. The voltage signal is then sent to the ECM for processing.

Bosch Design

Mass Air Flow Meter

The mass air flow sensors being used on vehicles today, calculate the air flow by heating up a grid or a wire and then monitoring the amount of current it takes to maintain the temperature at the grid. Any fluctuation in the current causes a frequency signal to be generated and sent to the ECM. The computer converts this signal into digital data and then processes the information along with the data in the PROM and RAM chips to calculate the correct air fuel ratio.

GM Delco Design

Ford Hitachi Design