EVALUATION METHODS AND WAYS OF IMPROVING THE OPERATIONAL DEPENDABILITY OF MASS AIRFLOW SENSORS IN ENGINES
Authors: Gorban M. V. , Pavlenko E. A. 
Published: April 2021

The design of today’s car engine electronic control system practically always includes an engine load sensor. Normally, its role is played by the intake manifold absolute pressure sensor or the mass airflow sensor. Film mass airflow sensors are the most common ones. The sensor is installed in the intake between the air filter and the throttle plate of the engine intake manifold. In the process of operation the sensor is exposed to pollution and ageing of the gauging element due to interaction with dust particles and motor oil fumes in the airflow. That causes the output signal to deviate from the reference values and consequently inaccurate calculation of the fuel blend composition by the electronic engine control system. Given the design of the sensors, they cannot be repaired and are replaced with new ones. A new sensor is quite costly. Given the above, it is obvious that the subject is of relevance. The aim of the paper is to find methods of evaluation and ways of improving the operational dependability of film mass airflow sensors installed in modern automobiles. The evaluation of sensor operability is based on the voltage of the sensor output signal. Using a diagnostic scanner plugged into the automobile’s diagnostics port in the analog-to-digital converter channel viewing mode the voltage of the sensor output signal is recorded, the fuel blend long-lasting correction factor is evaluated, and the presence of error codes associated with the malfunction of mass airflow sensor in the memory of electronic control unit is verified. A digital oscilloscope is used for measuring the voltage at the moment of ignition lock activation and the resting voltage at zero airflow, as well as the transient time. Based on the obtained findings it becomes obvious that the operational dependability of such sensors can only be improved by correcting the calibration tables of the mass airflow sensor stored in the memory of the engine control unit. Using a mass airflow sensor test stand, input data is prepared for the correction procedure. The reference and tested sensors are installed on the same vacuum pump nozzle, and the airflow rate is changed gradually. Under a fixed airflow rate the sensors’ output voltage is measured. The resulting data is summarized in a table and processed with the Chip Tuning PRO calibration software. As can be seen, one of the causes of the loss of the sensors’ operational dependability is the pollution of the sensing element. The layer of pollution on the sensing element reduces the coefficient of heat transmission between the airflow and the sensor’s gauging element. Based on the conducted research, the paper presents the results of changing sensor output signal in operation as compared to the reference values, suggests a method of correction of the calibration table of mass airflow sensor parameters in the engine control program stored in the memory of the electronic control unit, provides recommendations regarding the methods of evaluation and ways of improving the sensors’ operational dependability.