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Reduction of NO X emissions and fuel consumption are the main topics in engine development, forcing the adoption of complex techniques and components, whose interactions have to be clearly understood for proper and reliable operations and management of the whole system. The investigation presented in this paper aimed at the development of integrated control strategies of turbocharging, high pressure (HP) and low pressure (LP) exhaust gas recirculation (EGR) systems for better NO X emissions and fuel consumption, while analyzing their reciprocal influence and the resulting variations of engine quantities. The study was based on an extended experimental program in three part load engine operating conditions. In the paper a comparison of the behavior of the main engine sub-systems (intake and exhaust circuits, turbocharger turbine and compressor, HP and LP EGR loops) in a wide range of operating modes is presented and discussed, considering open and closed loop approaches for variable nozzle turbine (VNT) control, and showing how these affect engine performance and emissions. The potential of significant decrease in NO X emissions through the integration of HP and LP EGR was confirmed, while a proper VNT management allowed for improved fuel consumption level, if an open loop control scheme is followed. At higher engine speed and load, further actions have to be applied to compensate for observed soot emissions increase.

Downsizing and turbocharging are today considered an effective way to reduce CO2 emissions in automotive gasoline engines.\ud To this aim, a deep knowledge of turbocharger behavior could be a key solution to improve the engine-turbocharger matching\ud calculation. The influence of the intake system geometry on the surge line position is an important aspect to guide the project of\ud the intake manifold, enlarging the compressor stable zone. This aspect has a considerable impact on engine performance,\ud especially during transient operation. A wide experimental investigation was carried out at the turbocharger test facility of the\ud University of Genoa on a small turbocharger compressor. Compressor characteristic curves measured considering an automotive\ud intake circuit are compared with standard maps provided by turbocharger’s manufacturer. This information allows the\ud optimization of 1D model implementing more realistic maps of compressor. The influence of three different layouts has been\ud investigated varying overall circuit volume and length, keeping values in a range compatible with passenger cars packaging\ud constraints. In the paper, the main results of the experimental campaign are presented taking into account the influence of\ud geometry variations on compressor map and surge line position

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