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With growing demands for better fuel economy and reduced carbon emissions there is a need for smaller and more fuel efficient engines. At the same time, to improve passenger comfort there are also demands placed on improved vehicle quietness [1]. A Homogeneous Charge Compression Ignition (HCCI) system or a higher compression ratio system can be used to obtain better fuel economy but the enhanced combustion rate causes an increase in engine vibration in the medium to high frequency range [2, 3]. To ensure vehicle quietness, this issue of structure-borne noise that is transmitted from the engine mounts to the body must be addressed. In this paper a simple anti-vibration active mount system is introduced that can significantly reduce structure-borne noise at medium to high frequencies. This is achieved by adding mass to the insulator which leads to resonance at lower frequencies, in order to obtain double anti-vibration performance.

The respective contributions of combustion noise, mechanical noise, noise attributed to the fuel injection system and other engine noise components must be identified in order to devise effective measures for reducing diesel engine noise. This paper describes a method for estimating the contributions of engine noise components using multiple regression analysis. With this method, the engine noise level is regarded as a criterion variable and the cylinder pressure level and several parameters are examined as explanatory variables. The accuracy of this method has been confirmed by comparing the results with experimental data. It was found that, by selecting adequate parameters as explanatory variables according to the type of fuel injection system used, the respective contributions of combustion noise, mechanical noise and fuel-injection noise estimated by multiple regression analysis agreed with the experimental data.

We have developed a vibration damping technique for the Oil Pan to reduce radiation noise. This technique makes use of oil viscosity. To increase vibration damping of oil pan, we use oil viscosity by forming a thin oil film between the oil pan bottom and an added inner plate. This paper presents the results of vibration tests that were conducted to study the oil damping mechanism and results of applying to a small high-speed diesel engine.