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Study of a New Scavenging System to Reduce the Loss of Fresh Charge in Three Different Types of Two-Stroke SI Engines
Published December 01, 1993 by Associazione Tecnica Dell'Automobile in Italy
An improvement in the design of a two-stroke SI engine, by which short-circuiting of the fresh charge through the exhaust port is considerably reduced, is reported here. In this design, two reed valves which are fitted at their transfer ducts, enable pure air alone to be introduced into the cylinder during the initial period of the scavenging process. The quantity of air to be inducted through the reed valves (secondary air) for the best performance depends on the engine operating conditions and displacement volume. It has been observed from the study of this new scavenging system that for large and medium capacity (150 cc and above) engines, a higher secondary air flow rate, achieved by regulating compressed air flow is desirable whereas for a very small capacity (55 cc) engine, there must be a control on the quantity of secondary air from the atmosphere itself in order to obtain overall improvement in the performance.