The use of bioethanol in the transport sector can contribute to mitigate the greenhouse gas emissions of the vehicles. To achieve this goal, together with a positive energy balance in global productive process of ethanol (well to tank), it is important that adding ethanol to gasoline does not cause a worsening of the efficiency of the internal combustion engine (tank to wheel). In this paper, a research activity on a commercial spark-ignition light-duty engine at the test bench is reported. The aim of the work was to characterize the effect of different bioethanol/gasoline blends on engine behaviour. Blends until 85% of ethanol were tested. Comparative studies of combustion development of gasoline and gasoline/ethanol blends at different concentrations have been made through the analysis of pressure cycles in combustion chamber. Moreover, emissions were collected and analyzed. Emissions downstream of the catalyst, measured with the blends, resulted quite similarly to the gasoline case. Instead, upstream the catalyst a reduction of emissions, proportional to oxygenated content was noted. Moreover, a general carbon dioxide reduction with ethanol blends was achieved due in particular to better engine thermal efficiency. 1. Introduction The increasing costs and climate change related to fossil fuels exploitation require a major share of the energy production from alternative sources, in particular from waste or renewable sources. Recently, great attention is given to the use of biomass to produce fuels, especially for transport as alternative to petrol. Biofuels production becomes extremely interesting when obtained from waste or residual of other human activities, but in this case, the limited feedstock could contribute only with a small impact on the reduction of the fossil fuel demand. The use of bioethanol in the transport sector can contribute to mitigate the greenhouse gas emissions of the vehicles. The benefits are strictly connected with the efficiency of ethanol global productive process, taking into account also land use competition with other human needs. The octane number of pure ethanol is higher than gasoline; therefore, it is an optimal fuel to improve performance of Otto engines since the risk of knock decreases [1]. Ethanol can be used pure or mixed with gasoline. Anyway, the use of pure ethanol implies some problems during cold start due to vaporization lower than gasoline, which in some cases should require an electrical preheating of the engine block [2]. Also the problem of corrosion implies that the fuel system must be made using
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