Abstract
Fuel conversion efficiency measurements are generally performed on dedicated engine dynamometers that ensure good accuracy. This work investigates an alternative method for measuring fuel conversion efficiency of an automotive engine using a chassis dynamometer. Other studies performed in a similar manner only present an overall power train efficiency level, including the transmission. By using full load measurements, this study proposes a method for calculating fuel conversion efficiency for the engine rather than the overall power train. Acceleration and steady state trials recorded using a spark ignition engine powered passenger car were analyzed in order to evaluate the capability of the proposed method. It was found that only the steady state trials ensure the required accuracy level throughout the engine speed range, while the measurements performed during acceleration only showed plausible results at the top end of rotational speed. The main reason for this finding was the differences in measured fuel consumption values, given that all other parameters, such as intake air pressure and temperature, spark advance, relative air–fuel ratio and power output were within comparable range for both procedures. As a result, only steady state trials are recommended when performing fuel conversion efficiency measurements using a chassis dynamometer.
Keywords: automotive engine, fuel conversion efficiency, chassis dynamometer, full load trials.