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The problems of Two-Stroke SI engines regarding high fuel consumption and unburned hydrocarbon emissions, both caused by the short circuiting of fresh homogeneous mixture during the scavenge process, are well-known. The progress of Piaggio since 1977 in state-of-art direct fuel injection systems, oriented to development of Hi-Tech solutions for 2T SI engines to overcome the above drawbacks, is analyzed. The analysis includes several streams of research ranging from conventional crankcase scavenged engines with direct solid mechanically controlled fuel injection to solutions with separate scavenging pump with electronically controlled injection units, and from low pressure injectors to air-assisted fuel injection with stratified charge. Each solution is examined with presentation of typical engine parameters and cost data.

Following general considerations on the present state of commuter traffic in the downtown sections of the cities, the specifications of an highly efficacious and efficient vehicle for individual transportation are analyzed. A two-wheeler vehicle appears very attractive when pollution and noise are overcome. A new formula of vehicle is so presented looking for a minimum optimun solution to the problem. The basic feature consists in an hybrid propulsion system, namely: internal combustion engine with catalytic muffler for downtown approach and an accumulator powered electric motor during restricted area trips. After the presentation of the experimental results, some considerations on utilization coefficient as well as energy use efficiency, in comparison with other modes of transportation, are presented.