Summary

Internal combustion (IC) engine is classical rotating machine that must be operated under various conditions. Sound and vibration signal of IC engine often give much dynamic information of mechanical system condition. Vibration and angular velocity of crankshaft signal on Ford Fiesta engine 1,3 dm3 were used for the tests. The tests were carried out in Bosch FLA 203 roller bench. The sampling frequency was 25 kHz and during data acquisition process, the rotating speed of the engine was kept at a constant rpm and at run up condition. The energy state of the pistons and the connecting rods is determined by the mean angular speed and the angular positions of the crankshaft. Changes in the pressure in cylinder caused by compression faults or misfire will affect directly the instantaneous angular speed of the crankshaft and vibration energy. In this paper engine exhaust valve fault and its influence over the instantaneous angular speed waveform and vibration of engine head is presented. Engine position sensor is one of part of the IC engine control system, thus an instantaneous angular speed based fault detection system does not require additional sensors. It can be seen from example of the present paper, when the valve worked abnormally, the vibration energy is moved forward towards the high frequency region (larger than 8 kHz)