1989-09-01

Improvement of Fuel Consumption of Two-Stroke Engines Applying CVT 891752

Although two stroke cycle engines generally have less mechanical parts and higher specific power output, the fuel consumption is considered inferior to that of four stroke cycle ones. Nevertheless, for motorcycles with a 100 cc engine which are used as an practical means of transportation 1) Two stroke cycle engines have revolution region which provides specific fuel consumption (SFC) as favorable as that of four stroke cycle engines, at a part throttle adjustment. 2) Applying centrifugal governor type V-belt CVT (continuous variable transmission) allows to always utilize a certain revolution region of the engine. Through the experimental approach and results based on the above concept, this paper reports that the optimum combination of two stroke cycle engine and CVT enabled to achieve fuel consumption as favorable as that of four stroke cycle engines. The attempt of improvement of fuel consumption was mainly conducted by “city running mode” which simulates the city driving of Pune City, India.Prior to the development, the basic engine characteristics were improved and the city running mode was cetegorized into i) idling region, ii) centrifugal clutch slipping region, iii) CVT ratio change region and iv) coasting region. Measures and optimizations were carried out on each of the regions. As a result, approximately 30% reduction in fuel consumption in both the mode fuel consumption rates and the actual running fuel consumption rates were achieved as compared with that of conventional two stroke cycle engines. Moreover, the minimum SFC (BSFC) at bench tests was 230 g/ps·ft (310 g/kw-h) with a part throttle of 20%.

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