COAST DOWN TEST – THEORETICAL AND EXPERIMENTAL APPROACH

Abstract

The paper presents considerations about the utility, suitability and limits of the coast-down experimental test in the automotive research. That test consists in launching of a motor vehicle from a certain speed with the engine disengaged and ascertaining of the current speed and distance covered during the free rolling, till vehicle stops. First it is indicated a modality to determine by computation the vehicle kinematics. There are presented the vehicle resistances, the assumptions and the values influencing the analyzed process. Then, there are established the mathematical equations necessary to ascertain the speed and distance during cost-down. By the analysis of the different factors influences it can be determined the necessary precision of measurements, so that the results of the test might be conclusive. Reciprocally, when experimental data exists, mathematical methods based on regression are presented to estimate the vehicle movement resistances. In the paper are presented data obtained using coast-down method with different test vehicles and in various road conditions. The results include estimated values for the rolling resistance coefficient and aerodynamic drag coefficient. New ideas for additional valorisation of the method are also indicated.