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Japan Automobile Research Institute has devised and evaluated the various fuel consumption measurement methods for fuel cell vehicles (FCVs). The examination covers the methods based on measurement of electrical current, hydrogen pressure/temperature, weight and flow rate that are expected to be the same accuracy and convenience as conventional measurement methods such as carbon balance method or fuel flow measurement method. As a result of examining the measurement accuracy for each method with a sonic nozzle used as a standard, it is found that both the pressure method and the weight method fulfill the target accuracy of ±1% and that the flow method is able to improve the accuracy by means of calibration with hydrogen. Also, as a result of applying each method to the fuel consumption test of FCVs, the relative error between the pressure method and weight method is within ±1%.

A new method to measure accurately the compression ratio of automobile engines in the manufacturing line is proposed. To determine the compression ratio of an engine, the cylinder volume at a piston position is measured with a detecting probe which is featured with a pressure sensor of high sensitivity and a micro piston driven by an electromagnetic coil. The probe is attached to the cylinder head at the spark plug hole. The air in the cylinder at TDC is compressed sinusoidaly at a frequency of 70Hz by the micro piston with a diameter of 5mm. The volume at TDC can be determined by detecting the pressure change caused by the compression by the micro piston. In this report, the principle of the method is described and effects of geometry of the chamber space and other parameters on the measuring accuracy are discussed. Polytropic exponent of the pressure change was found most crucial in this method.