Abstract: Combining with the development level and development trend of automotive fuel consumption test technology, and adopting the ultrasonic technology and single-chip microcomputer control technology, a research was made on the automotive fuel consumption test technology. The mathematical calculation model of automobile fuel consumption test was established based on the fuel consumption test theory of ultrasonic time difference method. The fuel flow rate was modified by means of flow correction coefficient based on fluid mechanics theory. Analyzing the geometry parameters’ influence of the ultrasonic flow sensor on automobile fuel consumption test, and using the 3 d coordinate method, the ultrasonic flow sensor’s geometry parameters can be accurately calculated. By analyzing the environmental temperature’s influence on the flow rate correction coefficient and the propagation velocity of ultrasonic wave in the fuel, modification measures were put forward. Quantitatively analyzing the parameters of sound and threshold value which influence calculating ultrasonic transmission time, eliminating the frequency noise using the maximum likelihood estimation method, and reasonably choosing the threshold value, the simulation results showed that automobile fuel consumption testing accuracy was up to 12 ns. Comprehensively taking into account the influencing factors of fuel consumption test and taking corrective measures can optimize the mathematical calculation model of automobile fuel consumption test, and improve the automobile fuel consumption test accuracy. Thus, it will lay a theoretical foundation for the research and development of an ultrasonic automobile fuel consumption testing instrument.

Key words: automobile engineering;fuel consumption testing;influence factors;ultrasonic wave;time difference method;testing precision