Abstract: Abstract: With the rapid growth of automobile ownership in China, the control of automobile fuel consumption is not only an energy problem, but also an environmental one. The carbon balance method is a major, indirect way of testing the automobile fuel consumption with high precision, but the test equipment is expensive, bulky, and hard to move, and the demands of the test environment are high; the sampling connection needs sealing and connecting to the exhaust pipe, so its application is limited. The direct test method tests the automobile fuel consumption through measuring fuel volume and quality within a certain distance or time, and the engine oil circuit needs to be taken apart in order to put in the fuel consumption meter. This method is inconvenient, time-consuming, and poses a security risk, which affects the test precision. At present, the electronic fuel injection system (EFI) engine adopts a special EFI fuel consumption sensor to test automobile fuel consumption, or uses two sets of ordinary flow sensors. Its testing principle is roughly the same: They all concatenate engine oil flow sensors to fuel line of engine, they are complicated operations, and the signal lag of the sensor is greater. Because the fuel injection pressure of the EFI engine is high, the amount of oil return is greater, and the oil temperature is higher, which may easily cause the return pipe of connection on the sensor to inflate and explode. Aiming at the existing problem of automobile fuel-consumption testing, using the single chip microcomputer control technology, we tested automobile fuel consumption through direct measurement of the fuel injection pulse width. We then developed an intelligent testing instrument for automobile fuel consumption. The injection pulse signal from the engine ECU is directly collected by the automobile fuel consumption test system. After it is filtered and embedded into single-chip microcomputer, the injector's cumulative injection time and the number of fuel injections is detected by the single-chip microcomputer, the fuel injection pulse width is obtained, and the relationship between the quality of engine fuel consumption and the injection pulse width is determined. According to EFI controller principles, we determined the testing method for automobile fuel consumption. Based on fuel consumption testing principles, we built a mathematical model of an automobile fuel-consumption testing system, and corrected the mathematical model in standard conditions. According to the function requirements of the fuel-consumption testing system, we determined the single chip microcomputer model and modules function of automobile fuel consumption test controlling system, and designed the injection pulse signal acquisition system and the main program for the automobile fuel-consumption test system. We structured the trial system on a testing prototype using the automotive fuel consumption prototype and the automotive dynamometer test bench. Through analyzing and processing the trial data, the testing precision of the automobile fuel consumption prototype is up to 0.46%. Engine speed has an important impact on injector characteristics parameters, and it will influence automobile fuel consumption testing accuracy. Injector characteristics parameters under different engine speed conditions were amended using a linear regression method that will further improve automobile fuel-consumption testing accuracy. The research will provide the reference to develop high-precision, intelligent automobile fuel-consumption test equipment.