Effect of driving resistances on energy demand and exhaust emission in motor vehicles

Among the fundamental factors affecting the emissions of internal combustion engines is the resistance to motion acting on the car. This is an important factor to be taken into account when testing cars in conditions simulated on a chassis dynamometer. The dependence of the driving resistance function on vehicle speed is determined on the basis of various methods, the most frequently used of which is the so-called alternative method specified in procedures for the type approval of motor vehicles with respect to the emission of pollutants in exhaust gases. The values adopted in accordance with the alternative method differ from the actual resistance acting on the car in road conditions. This is one of the reasons why the emission of pollutants and the fuel consumption of an engine in real road conditions differs from the values given by the car manufacturer, including the emission limits specified in the standards. This paper presents an evaluation of the influence of driving resistance on the energy demand and emission of pollutants in the exhaust gases by sample passenger car with SI engine fuelled by petrol and LPG.