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An evaluation of emission levels and fuel consumption of urban hybrid vehicles has been performed. Both heavy and light duty vehicles have been considered and a comparison on specific consumptions and emissions has been carried out between the hybrid and traditional configurations. The battery behavior during charge and discharge transients has been taken into account because it is one of the most critical elements of hybrid systems. The results of this investigation indicate the possibility to reach significant reductions of consumption and emissions through the adoption of hybrid systems for urban transports.

The behaviour of two combustion chambers, a toroidal and a turbulent one, has been compared. The engine performance in terms of imep and exhaust emissions were measured. Laser Doppler Anemometry technique was used to characterize the fluids dynamic aspect of combustion system. The axial asymmetry introduced in combustion chamber shape causes strong differences in the air flow field at the end of compression stroke. The tangential velocity profile is flattened to that obtained with toroidal chamber. Moreover the rms values of tangential velocity measured in turbulent combustion chamber are about three times higher than that measured in the toroidal chamber. At low engine speed the turbulent chamber allows to operate with low NOx levels without penalties of smoke emissions and fuel consumption as happens by using conventional toroidal chamber.