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The paper presents an approach to reconstruct cylinder-individual pressure of each combustion cycle by processing the instantaneous fluctuations of the engine speed and the in-cylinder pressure of one cylinder. A new pressure model with a feasible number of parameters is combined with a model-based torque estimation in order to reconstruct the pressure traces. The performance of the proposed algorithm is demonstrated with measurement data acquired from a vehicle with a four cylinder spark ignition (SI) engine.

The resonances of SI engine combustion chambers are slightly excited during normal combustion but strongly excited by knock. In order to avoid knocking combustions extensive knowledge about knock and its effects is necessary. In this paper the combustion chamber of a serial production engine is modeled by finite elements. Modal analyses are performed in order to gain information about the resonances, their frequencies, and their frequency and amplitude modulations. Simulation results are compared to measured data using a highresolution time-frequency method. Furthermore, a connection between knock origin and the excitation of the resonances is postulated applying transient analyses.

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