Interlaboratory Correlation of Chassis Dynamometer Test Results

The testing of passenger car fuel consumption and exhaust emissions is carried out on chassis dynamometers of various makes and specifications. Correlation of results from different installations may be carried out at regular intervals using a specially prepared vehicle containing a stable engine (for exhaust emissions), torque transducers, a fuel flow meter and an electronic data acquisition system. However, basic problems, such as establishing a consistent relationship between wheel speed of the test vehicle and the surface speed of the idler roller have received little attention.

The present paper discusses these and other problems encountered in an interlaboratory correlation round involving more than 100 drive cycle tests in nine different chassis dynamometer laboratories throughout Australia. A method is presented of setting the tyre rolling circumference of the instrumented test car, which largely eliminates the wheel speed anomaly. In addition, a data analysis procedure, which separates absorbed power into components of friction, drag and inertia, has been used for diagnosing dynamometer and fuel consumption differences.