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Vibrations Associated with the Quality of Combustion Derived from Induced Failures in a Spark Ignition Engine

Abstract:

The present investigation aims to analyze engine vibrations and HC emissions when causing faults not detected by the on-board diagnostic system (OBD II) in the air induction system and the ignition system of a gasoline vehicle. First, experimental measurements were performed with a vibration analyzer and a unidirectional accelerometer mounted on the engine block. In parallel, hydrocarbon (HC) measurements were performed to contrast the influence of combustion with the simulated failures. Secondly, signal processing was performed by applying the fast Fourier transform to a set of blocks superimposed on an interval of 512 points, in order to force the periodicity of the signal and thus have the most information related to the degree of severity of the failures. The results obtained indicate that the failure of a spark plug causes higher vibrations in the engine, and this is associated with a higher amount of HC amounting to 188 ppm for the use of fuel with a RON of 87.