The Development of a High-Performance Motor-Cycle Engine

Abstract

The design of medium capacity, high specific output, two-stroke cycle engines is of increasing interest due to the expanding market for motor cycles and leisure vehicles, particularly in the United States. It is felt that there is a growing need to apply modern techniques to this design process, which covers the entire spectrum of mechanical engineering from fluid mechanics to stress mechanics. This paper describes the effective utilization of a high speed digital computer for those calculations connected with the unsteady gas dynamics of flow in the exhaust and transfer systems, the stressing of the connecting rod, the balancing of the crankshaft, the design of the combustion chamber, and the analysis of the porting of other high-performance engines so that an information library is stored. A method of experimentally determining loop-scavenging efficiency is evaluated. Further, a unique method of asymmetrically timing the inlet process of a two-stroke cycle engine is described and its initial development reported. The design of a complete engine, of 250 cm3swept volume, is detailed and its road and test-bed performance characteristics appraised. The engine produces 180 hp/litre as a specific output, at initial testing.