The subject of the considerations described in the paper is the problem of early detection of abnormalities and damages during operation process of the turbo diesel engine with small volume displacement and direct fuel injection, which is used in modern LDV vehicles dedicated especially for urban areas, in the context of present and future requirements for a technical object diagnostics, taking into account the criteria of optimizing overall efficiency, toxic compound emission and safety of the

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... object in real conditions of its operation. The paper presents the results of empirical research of vibroacoustic signal application to the diagnostic evaluation of correctness of short-time engine main processes. The evaluation of the combustion process variability from structural and operational abnormalities by using dimensionless estimates of a vibration process was conducted, and functional characteristics necessary to built the diagnostic algorithm in accordance with the requirements of on-board diagnostics were obtained.