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Simulation based design and control optimization is widely used to assist the development of highly complex modern downsized turbocharged gasoline direct injection (GDI) engines. In such engines, knock phenomenon is a major constraint that limits performance and fuel economy enhancements. Thus, an accurate knock prediction model is critically important for virtual engine development process. In this paper, an enhanced ignition delay model is proposed for spark ignition (S)I combustion model based on previously developed empirical two-stage ignition delay model using fuel blends [1]. The ignition delay model provides a capability of predicting ignition delay of the end-gas zone for different fuel blends without additional calibration when fuel blending ratio changes. To adapt the ignition delay model to the SI combustion environment, the model is modified to have the sensitivity to the dilution effect by residual gas.

Hyundai/Kia Motor Company will introduce new Kappa 1.6L GDI engine dedicated for hybrid vehicles, starting production for Korean market in the early 2016. It has achieved the challenging level of 40% maximum thermal efficiency as a gasoline engine. Even though it has the highest fuel efficiency, it can generate sufficient power to provide vehicle's dynamic driving performance. The new Kappa 1.6L GDI engine has been developed focusing on the fuel efficiency. To maximize fuel efficiency, compact combustion chamber is designed with 1.35 stroke-bore ratio. And other key technologies such as Atkinson cycle with high compression ratio, cooled EGR system with high energy ignition coil and high tumble intake ports are applied. The knock has been suppressed significantly to improve fuel efficiency by split cooling system with two thermostats and block insert, the piston cooling jet and the sodium-filled exhaust valve.