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Automotive companies are trying to enhance the customer’s impression by improving engine sound quality. The target of this sound quality is to create a brand sound that is preferred by their customers as well as quietness of interior noise. Over the past decade there have been many studies in the field of automotive sound quality. These have included the technologies such as tuning of intake orifice and exhaust orifice, tuning of structure-borne, intake feedback devices, active exhaust valves, ANC (Active Noise Cancellation) and ASD (Active Sound Design). The three elements of the sound that affect the feeling of the customer are known as engine order arrangement, frequency balance, and linearity. Here, the most important thing in sound quality development is the order arrangement.

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.

In a multi-cylinder variable valve lift (VVL) engine, in spite of its high efficiency and low emission performance, operation of the variable valve lift brings about not only variation of the air-fuel ratio at the exhaust manifold, but also individual cylinder air-fuel ratio maldistribution. In this study, in order to reduce the air-fuel ratio variation and maldistribution, we propose an individual cylinder air-fuel ratio estimation algorithm for individual cylinder air-fuel ratio control. For the purpose of the individual cylinder air-fuel ratio estimation, air charging dynamics are modeled according to valve lift conditions. In addition, based on the air charging model, individual cylinder air-fuel ratios are estimated by multi-rate sampling from single universal exhaust gas oxygen (UEGO) sensor located on the exhaust manifold. Estimation results are validated with a one-dimensional engine simulation tool.