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The benefits of a well optimized carburetion, over the entire engine utilization range, are well known especially in conjunction with a catalytic aftertreatment of engine exhaust gas. Today, electronic injection systems appear very effective for the solution of the above mentioned problem, but their complexity, i.e. the number of components and the necessity of high current rates, and costs preclude their practical application on small engines. The proposed system, that maintains the simplicity of the standard carburetor and requires only small driving currents, for the simplified electronics, could represent a sound solution. In a first part, after a description of the system, flow bench tests are reported. In a second part the results of the practical applications on two different types of small motorcycle are presented. A detailed analysis of the parameters influencing the repeatability is also carried out.

The Hi-Tech Two-Stroke SI engine is finding good appreciation in various fields of vehicle application and the final solution appears to include air assisted direct fuel injection and several solutions are now evaluated by the major world engine manufacturers. Those solutions anyway are poorly tailored to be fitted on very small engines such as for moped or light scooter applications both for the complications they require, consequentely the costs, and the difficult tuning of low load and idle caused by the very low quantity of fuel per cycle required. The proposed completely mechanical solution instead does consent with small modifications to the engine, only a new cylinder head is in fact required, to manage very well the engine all over its utilization range. After general considerations of the philosophy of the system and on the main parameters evaluation, a practical application on a 50cc scooter engine is described.

After some general considerations about energy utilization by different types of vehicles when used in urban areas, the possibility of improving moped performances by means of simple carburation and engine modifications is evaluated. Positive results are achieved in this research and the show that decidedly the moped is at the first place as regards energy economy in urban areas transport. This implies that, in a short time, it will be available a class of vehicles which, besides offering energy utilization coefficients little lower than those of public transport vehicles, will be characterized by the advantages of individual transport and, moreover, will contribute to reduce traffic congestion in urban areas.

The emission standards compliance is really becoming effective generally for all the class of engines and particularly for two-stroke SI. While for larger capacity and more valuable applications, such as scooters, snowmobiles, marine engines, the state of the art appears consolidated with the use of direct fuel injection systems, the engines dedicated to very light and simple applications need a different approach in terms of simplicity and cost. Aiming in this direction a system including a self - sustained air injection system in the exhaust and oxidation catalysts was prepared. The influence of the main design parameters governing the system performances and their mathematical relationships were experimentally studied with the aid of a DOE (Design of Experiment) technique methodology.

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.

The advantages of air assisted direct fuel injection systems to achieve high atomization degree into the combustion chamber of SI engines are well-known. The solutions up to now proposed appear anyway poorly tailored to be suitable for small engine applications. In fact scaling down such existing systems for automotive applications, they present mainly two drawbacks: the costs and a difficult tuning of the very low quantity of fuel required per cycle. Moreover the amount of electric energy required makes the engines not self-sufficient. To overcome the above mentioned problems, Piaggio has developed a completely mechanical low cost fuel injection system, named FAST (Fully Atomized Stratified Turbulence), which does consent a very atomized and stratified mixture lean combustion process, i.e. a dramatic improvement of emissions and fuel consumption. After general considerations, the application of such system to a small capacity 2T engine is analyzed.