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The similar targets of future spark-ignition (SI) and compression-ignition (CI) engines consisting in the noticeable increase of specific power concomitantly with the drastic reduction of fuel consumption and pollution in a wide operation range lead to similar development of thermodynamic functions and technical solutions. The achieved modular level of implementation of functions and solutions in advanced piston engines allows to establish common development platforms for both SI and CI engines. Such functions are the scavenging management, the spray-guided mixture formation by fuel direct injection, the exhaust gas recirculation and the homogeneous charge compression ignition. Under the technical solutions to their generation there are the super- or turbocharging, the variable control of intake-and exhaust valves and the direct injection techniques by common rails or by high pressure modulation.

The optimization of a high performance engine in order to achieve maximum power at full load and high speed can cause an unstable behavior when the engine is running at different conditions, thus making a robust combustion diagnosis for on board diagnostic EOBD/OBD II purposes (misfiring detection) particularly challenging. In fact, when a misfire occurs, its detection can be critical because of the high background noise due to high indicated mean effective pressure (IMEP) cyclic variability. A partial reduction of the high IMEP variability had been achieved by optimizing control parameters of a new prototype high performance V8/4.2 l engine. Spark advance and VVT phasing maps had in fact been re-designed based on in-cylinder pressure variability (cycle by cycle and cylinder by cylinder) analysis.

The results of an extensive investigation developed on the wastegated radial flow turbine of a small automotive turbocharger are presented in this paper. Test rig measurements were performed to point out the influence of the by-pass opening on turbine performance. The analysis was extended both to steady and pulsating flow conditions, and controlled values of the main parameters of generated unsteady flow were obtained by a new dedicated turbine feeding line. A specific test method was followed in order to prevent inaccuracies in the definition of the waste-gate opening. The hypothesis assuming the turbine impeller and the waste-gate as two independent nozzles was studied in steady flow conditions. Turbine measured pulsating performance, which generally resulted higher than steady flow, was compared with the values supplied by analytical predicting models based on the quasi-steady flow assumption.