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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.

For optimizing the performance of SI engine such as engine torque, fuel consumption, and emissions, various types of system for variable valve timing were developed by many automotive researchers. In this paper, we investigated the relationship between valve timing and intake orifice noise, and suggested how to improve NVH (Noise, Vibration and Harshness) performance as well as engine torque. Some experiments using the engine dynamometer were carried over about 150 different operating conditions. BEM analysis was also conducted in order to calculate acoustic modes of intake system. The results show that the valve timing and overlap of breathing systems have influence on NVH behavior, especially intake orifice noise over whole range of operating conditions. Valve timing and overlap of intake and exhaust valve were optimized in the view of sound quality as well as overall noise level.

The development of a new method to evaluate the NVH quality of diesel combustion noise bases upon following questions by regarding typical driving modes: Driving behavior with diesel vehicles Which driving situation causes an annoying diesel combustion noise Judgment of diesel combustion noise as good or bad A suitable test course was determined to regard typical driving situations as well as the European driving behavior. Vehicles of different segments were tested on that course. The recorded driving style and the simultaneously given comments on the diesel combustion noise results to a typical driving mode linked to acoustics sensation of diesel combustion noise. The next step was to simulate this driving mode on the chassis dynamometer for acoustical measurements. The recordings of several vehicles were evaluated in listening test to identify a metric. The base of metric was objective analyses evaluating diesel combustion noise in relevant driving situations.

Driveline clunk is perceived as disturbing metallic noise due to severe impact at driveline components such as gear pairs when the engine torque is suddenly applied and transmitted to the driveline system. In this work, experimental method detecting the most contributive gear pair to the clunk generation was investigated and applied to mini van vehicle of front-engine and rear-wheel-drive. Another experimental method, TPA (Transfer Path Analysis), was employed to identify transfer path of the clunk. And then, driveline clunk model was developed using commercial multi-body-dynamics program, ADAMS, in order to further investigate the critical clunk mechanism and potential clunk reduction solutions by performing parameter study.

A comprehensive investigation was carried out in order to develop the idle sound quality for diesel V6 engine when the engine development process is applied to power-train system, which included new 8-speed automatic transmission for breaking down the noise contribution between the mechanical excitation and the combustion excitation. First of all, the improvement of dynamic characteristic can be achieved during the early stages of the engine development process using experimental modal analysis (EMA) & the robust design of each engine functional system. In addition, the engine structural attenuation (SA) is enhanced such that the radiated combustion noise of the engine can be maintained at a target level even with an increased combustion excitation. It was found that the engine system has better parts and worse parts in frequency range throughout the SA analysis. It is important that weak points in the system should be optimized.

Gear rattle is generated basically due to the impacts of unloaded gear pairs in transmission. The rattle noise level is determined by two main factors, excitation level at transmission input shaft and rattle sensitivity of the transmission at that excitation level. In this work, (1) the transmission rattle sensitivity was measured and investigated (2) torsional vibration model of driveline system was developed to estimate the speed fluctuation at the transmission input shaft and to find some rattle improvement potential by tuning driveline components so that the speed fluctuation be minimized.

This paper presents an advanced technique for noise reduction and sound quality analysis in direct-acting type of valve train system. Mechanical Lash Adjust (MLA) system has lower friction loss and simpler and lighter structure in comparison with Hydraulic Lash Adjust (HLA). Despite of such advantages, MLA system has a weak point which generates harsh impulsive noise whenever cam comes into contact or detaches suddenly from tappet during the valve operation in the ramp area. A sound quality analysis technique was used to analyze the detail noise and vibration characteristics during valve opening and closing operation respectively. This paper describes a procedure and advanced technique to identify noise sources and its generation mechanism by analyzing measured data taken from direct-acting valve train system. Subsequently, an optimum cam profile was redesigned and used in new Hyundai-motor V6 engine.