UBC Theses and Dissertations

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UBC Theses and Dissertations

Stratified charge scavenging of a two-stroke engine at part throttle Fandrich, Helmut Edward


The high speed 2-stroke cycle engine designed for high power-to-weight ratio is relatively inefficient at part throttle. It would be advantageous to incorporate a simple method of allowing extra air to enter the cylinder prior to the fresh mixture, thus stratifying the charge and increasing the proportion of the air-fuel mixture retained in the cylinder at part loads while not deleteriously affecting the maximum power at full throttle. A series of tests, on an engine fitted with a reed valve connecting the atmosphere to the passageway leading to intake ports, were carried out with varying amounts of extra air, the results showed that power, speed, thermal efficiency, and fuel trapping efficiency gave increases at nearly all settings, but with a large excess of extra air, the air-fuel ratio through the carburetor had to be decreased to maintain stable operation.

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