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The nowadays two-stroke engine technique is directed toward new concepts to reduce fuel consumption and pollution. Typical features are direct injection of fuel and no lost oil lubrication: a separate scavenging system is becoming so a must. Following general consideration about different scavenging pumps, a regenerative blower solution is proposed. Regenerative blowers present in fact several advantages in comparison with other solutions like simplicity in construction and on engine fitting, no maintenance and low cost. An exhaustive experimental evaluation was carried out on a direct injection two-stroke S.I. engine with a separate scavenge, already described in a previous work by one of the authors. The results show the practical feasibility of the proposed solution. In fact, the regenerative blower is suitable to match the engine air breath demand all over its utilization range.

Following the state - of - the - art analysis of typical applications of two-stroke SI engines in road vehicles, new solutions for this type of engine are examined. The two-stroke engine appears as an extremely attractive one during part-throttle opera tions especially from the point of view of fuel consumption, when the problems caused by fresh mixture short-circuiting are overcome. This fact is well confirmed by the renewed interest in the two-stroke cycle SI Engine. A new solution, with direct fuel injection and separate scavenging pump, that shows very low fuel consumption data down to very low B.M.E.P. levels while mantaining a high specific power output and acceptable HC emissions, is then presented.