A Study on the Effect of Exhaust Pipe System upon the Output of a Four-Stroke Cycle Small Gasoline Engine

To examine the effects of length of an exhaust pipe and engine speed in a small four-stroke cycle engine, the authors have measured the output of the engine and analysed some pressure diagrams for the exhaust pipe. Some conclusions obtained in such experiments are summarized as follow : 1) The maximum output occurs on account of the innertia effect of the exhaust system. 2) The maching conditions are expressed approximately by the following equation Q=cθ/12kNl where c : mean sonic velocity in exhaust system θ : period of exhaust port opening k : maching factor N : engine speed, r.p.m.l : length of exhaust pipe+correction value of open end. The maximum output occurs in case of Q≒1.