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One of the important factors affecting exhaust emissions of car engines is driving resistance. A certain problem during the tests bench according to the driving cycle is the road load curve function, which is determined based on various methods. In the paper, the results of studies of the impact of the driving resistances on the exhaust gas emissions of CO (carbon monoxide), CO2 (carbon dioxide), THC (total hydrocarbons), NOx (nitrogen oxides) emitted by passenger cars with a SI engine, fuelled with petrol and LPG were presented. Tests were carried out in chassis dynamometer for road load coefficient determined by the road method and for type approval alternative method. The research was realized for NEDC (New European Driving Cycle) cold start tests for EURO 3 and EURO 6 standards vehicles. Results show that CO2, CO and THC emissions for tests realized by dyno settings based on road load are higher than for tests with dyno settings by the alternative method of the load.

The legislative limitations of vehicle exhaust emission together with the current and prospective growth of road transportation intensity calls for continuous effort to improve vehicle powertrains that must be done both in design and technology domains. As the powerful remedy, a new generation of combustion engines fitted with the variable compression ratio (VCR) feature is considered. VCR technology can extend the range of clean engine operations such as HCCI or other advanced combustion strategies, enabling reduction of all exhaust harmful compounds simultaneously. There are several known technologies for performing variable compression ratio in combustion engines; some of them have been successfully tested in engine research rigs and/or vehicle prototypes. In the paper the proposal of application of variable compression ratio technology in four-cylinder, water-cooled engine is presented.