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A system for both ignition and ion current measurement was designed and set up at Istituto Motori. Particular attention was paid to the problem of dissipating the residual energy stored in the ignition coil, reducing the electromagnetic interferences and especially improving the response of the measurement system. In order to assess the capability of the ion current signal to give reliable and accurate information for knock detection, a number of tests were carried out at full load on a commercial PFI four cylinder engine, at various air/fuel ratios and spark timings. Some knock indices based on the ionization signal, both band pass filtered and non-filtered, were introduced, in particular: the Amplitude of the Second Ionization Peak (ASIP), the Mean not filtered Ionization Current signal (MIC), the Maximum Amplitude of Ionization Current signal Oscillation (MAICO), the Integral of Modulus of filtered Ionization Current signal Oscillation (IMICO).

The electromechanical devices proposed in technical literature are very flexible. However, their working principle (fixed lift, fixed lifting time and variable valve events) imposes the use of different strategies, such as cylinder or port deactivation to enable work at partial loads. This happens in particular at low loads. The present paper aims to evaluate the effect of the design and of the strategies adopted to vary the load (cylinder or port deactivation etc) on performance and on pollutant formation of a stoichiometric DISI engine. The calculations were performed by a commercial one-dimensional code (Wave produced by Ricardo). This tool was also used to give inputs to the design of the electromechanical actuator. The electromechanical design of the actuator was carried out with the aid of the code Flux2D produced by Cedrat. This code allows the complete simulation of transients and of the electrical losses of the actuator.

The paper gives a short outline of experiences gained at IM in the design of an electromechanical valve actuator having two magnets and two balanced springs. This device works at fixed lift, fixed lifting time and variable valve event. Some of most relevant topics regarding the design of such a type of actuator have been analyzed. In particular, in the first part of the paper the problems of varying load have been tackled with the aid of a commercial one-dimensional code. Based on these results, the electromechanical design of the actuator has been started. Three axial-symmetric geometries have been compared using an electromagnetic CAD. The requirements of systems to perform the first lift at engine start up and the catching in operation have been analyzed. The evaluation of energy losses connected with these phases has been also done.