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In the last few years, the automotive industry had to face three main challenges: compliance with more severe pollutant emission limits, better engine performance in terms of torque and drivability and simultaneous demand for a significant reduction in fuel consumption. These conflicting goals have driven the evolution of automotive engines. In particular, the achievement of these mandatory aims, together with the increasingly stringent requirements for carbon dioxide reduction, led to the development of highly complex engine architectures needed to perform advanced operating strategies. Therefore, Variable Valve Actuation (VVA), Exhaust Gas Recirculation (EGR), Gasoline Direct Injection (GDI), turbocharging, powertrain hybridization and other solutions have gradually and widely been introduced into modern internal combustion engines, enhancing the possibilities of achieving the required goals.

The paper reports the research activity related to the development of a twin-spark SI engine equipped with a variable valve timing (VVT) device. Improvements on the fuel consumption at part load are expected when an high internal exhaust gas recirculation (internal EGR) level is realized with a proper phasing of the VVT device. The twin-spark solution is implemented to improve the burning speed at low load, and to increase the EGR tolerance levels. Both experimental and theoretical analyses are carried out to investigate the real advantages of the proposed engine architecture. In particular an original quasi-dimensional model for the simulation of the burning process in a twin-spark engine is presented. The model is mainly utilized to find the proper combination of VVT device position (and hence EGR level) and spark advance for different engine operating conditions. A comparison with the single-spark solution is also provided.

Over the last decades, internal combustion engines have undergone a continuous evolution to achieve better performance, lower pollutant emissions and reduced fuel consumption. The pursuit of these often-conflicting goals involved changes in engine architecture in order to carry out advanced management strategies. Therefore, Variable Valve Actuation, Exhaust Gas Recirculation, Gasoline Direct Injection, turbocharging and powertrain hybridization have found wide application in the automotive field. However, the effective management of a such complex system is due to the contemporaneous development of the on-board Engine electronic Control Unit. In fact, the additional degrees of freedom available for the engine regulation highly increased the complexity of engine control and management, resulting in a very expensive and long calibration process. To overcome these drawbacks, an effective methodology based on the adoption of 1D thermo-fluid dynamic analysis is proposed in this study.