Assessment of the vibroactivity level of SI engines in stationary and non-stationary operating conditions

Combustion engines are one of the main sources of vibration and noise in vehicles. The level of engine vibroactivity is affected by aspects such as rotational speed and technical condition. Tests were carried out as part of the research, designed to assess the level of vibroactivity of SI engines in stationary and non-stationary conditions. During the bench tests, the engine's rotational speed and its technical condition were changed by simulating a slightly enlarged valve clearance. As a result of the experiments it was determined that local changes in the amplitude of engine vibrations caused by the combustion process, clearances or misfire can be used as diagnostic information about the condition of the engine. It has been shown that the local level of vibration is dependent on the point of measurement, the angle of the crankshaft rotation and valve timing, and that for diagnostic tests, measurements performed in stationary engine operating conditions are more useful. The tests have also shown how the change of engine condition affects the level of noise and vibration generated, and how these levels change during the acceleration of the engine.