| Summary: | Problem. Single-cylinder four-stroke engines are used as a power plant for vehicles participating in international economical competitions Shell «Eco-maratthon». Many of the teams in the qualification «Forced-ignition internal combustion engines» use HONDA GX 25 and GX 35 engines. Therefore, it is important to know the mechanical losses of such engines to find ways to reduce them. The aim of the study is to determine the mechanical losses by scrol-ling the crankshaft with an electric motor DC-ED-25. For experimental determination of mechanical losses of the GX 25 engine, a special stand was created on the bed of which the tested motor and electric motor are mounted. The paper proposes a methodology for conducting an experimental study and the results obtained by two methods of mounting an electric motor on a bed. In the first case, the electric motor was fixed rigidly on the bed. In this case, the electric power was determined and, knowing the efficiency of the electric motor, the power of mechanical losses was determined. In the second case, the motor housing was installed in rolling bearings with the condition of free rotation around the axis. During the tests, the mechanical moment acting on the body was determined using a strain gauge. Good experimental data were obtained in different ways. After statistical processing of the research results, empirical dependences for power and average pressure of mechanical losses are proposed. The method of scrolling the engine crankshaft by an external source is characterized by the simplicity of organization and measurement during the experiment. However, a more reliable method for determining mechanical losses is the method of comparing the indicator and effective power.
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