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Hyundai has developed a brand new 3.0L V6 diesel engine for luxury vehicle with electronic VGT, piezo injector and bedplate block structure. In addition to challenging targets for fuel consumption and emission levels, engine specifications were focused on performance and NVH. This paper presents the detailed process of reinforcing engine components such as block, cylinder head and oil pan in view of low sound pressure and high quality. Generally, the fast reaction speed of piezo injector can improve the emission, but it usually causes injector noise. We reduced this noise through developing new ECU logic and isolating this part with noise reduction foam. In addition to that, we could reduce the combustion noise using DoE method for the optimization of injection parameters considering the emission and fuel economy. As a result of these attempts, 3∼4dBA of overall sound pressure level from engine itself could be reduced without any loss of fuel economy and power characteristics.

The crankshaft torsional vibration angle is measured from a running engine, using a toothed wheel attached to the front of crankshaft. The torsional vibration stress near the node of torsional vibration is also measured by using strain gages mounted on the journal of crankshaft in a running engine. A theoretical analysis of torsional vibration of crankshaft is performed with a simplified model subject to the excitation torque. The comparison between the theoretical and experimental results shows that the idealized approach is applicable to predict the torsional vibration of crankshaft. It is found that the torsional vibration of crankshaft is mainly dependent upon the characteristics of rubber damper, i.e., the stiffness and damping coefficient of rubber, and the inertia of damper ring. It is recognized that the rubber damper should be carefully selected considering the variation in the dynamic characteristics of rubber.