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ESTIMATION OF FUEL SPRAYING FROM DIESEL ENGINE INJECTOR USING MULTIRESOLUTION WAVELET ANALYSIS OF VIBROACOUSTIC SIGNALS Piotr Boguś1,2, Mateusz Dedo3, Rafał Grzeszczyk3, Adam Wrona3, Jarosław Markowski4, Jerzy Merkisz4 (1) Rail Vehicles Institute „TABOR”, Poznań, Poland (2) Department of Physics and Biophysics, Medical University of Gdańsk, Poland piotr.bogus@gumed.edu.pl, tel. 604-126-032 (3) Automex sp. z o.o. , Gdańsk, Poland (4) Technical University of Poznań, Institute of Combustion Engines and Machine Construction, Poznań, Poland ABSTRACT The paper presents the application of wavelet multiresolution analysis to injection diagnostic using vibroacoustic signals. The use of wavelets in this area gives new perspectives of diagnostic applications. The vibroacoustic signals were acquired in a research bench for testing the Diesel engine injectors. This measurement of vibroacoustic signal is carried out using mems accelerometer mounted to a reactive cylinder with real injector placed centrally inside it. The reaction cylinder diameter reflects average dimension of real engine cylinder. Estimation of fuel spraying parameters was done by comparison of recorded vibroacoustic signals of correctly working injector and injector with simulated malfunction resulting in incorrect injector stream. For each original signal the 6 multiresolution approximation components were taken into account and for each signal and all it components such parameters as average value, standard deviation, average of absolute values and shape factor were calculated. For chosen components and parameters the suitable classifier was designed to distinguish between correctly and incorrectly working injector. The first results indicated that the comparable measurements must be performed for the same fittings of injector and accelerometer. Another key problem defining efficiency of developed algorithms was selection of the right value of a classifier threshold parameter. Satisfying this requirement, the research results presented in the paper proved that some signal parameters obtained for high frequency, multiresolution components can be used as diagnostic parameters for fault detection in injector testing bench applications.