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The introduction of piezo-electric sensor on mass produced engines for in-cylinder pressure measurement represents a near future step in order to improve combustion control. Piezo-electric sensors provide pressure measurements affected by offset error and drift due to thermal sensitivity: a pressure reference is needed for each cycle in order to obtain the actual pressure value (pegging). Three methods for the evaluation of the offset, based on the hypothesis of polytropic compression, have been analyzed in this work: (1) a three-point referencing method, (2) a linear least-square method and (3) a non-linear least-square method. From such a comparison the three-point referencing method appeared the best suited for on-board calculation since it has the lowest computational cost even if it suffers from noise sensitivity. Hence, the accuracy and the efficiency of this method have been improved by means of an original methodology.

In view of the incoming laws concerning the emission limits during test cycles, it is increasingly important reducing emissions at low and medium loads by using exhaust gas recirculation (EGR) techniques. The development of control strategies can be greatly improved by simulation models able to predict accurately the behaviour of the engine and its emissions in the entire field of operation, and specifically at low loads when the turbocharger is operated at low rotational speed and in the vicinity of the surge line. Often the maps of compressor and turbine made available by the manufacturer are not extended to low rotational speeds and low pressure ratios. Methodologies have been therefore developed in order to extend the available characteristic curves to other working points, taking into account the geometry and the rotational speed of the turbocharger. For the compressor, a technique based on the fluid dynamic similitude is proposed.