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Valve spring surge is one of the critical issues in an automotive engine that may cause catastrophic failure in an engine. The term surge refers to inter coil vibration of valve spring, which occurs when the natural frequency of the spring matches with the engine operating frequency. This surge happens when the engine speeds-up beyond the design limit under certain extreme operating conditions. The speed at which the valve spring surges is referred as valve spring surge speed. At this speed, the spring force starts deteriorating and eventually results in loss of contact between the valve train components. So, there is a need to predict the engine speed at which the valve-train components start losing contact and also explore possibilities to increase the surge speed by optimizing the valve spring design parameters. This paper is a physical extension of theoretical prediction of valve jump phenomenon for existing and proposed valve springs using multi-body dynamic ADAMS software® [3].

The crankshaft twist is of great concern for heavy duty engines. In order to have a longer B10 life and better NVH characteristics, it is desired to have minimum Torsional vibrations (TV) in the crank shaft. To keep the crankshaft twist in check - TV dampers are used. Aneasier approach is to use a Viscous TV damper which keeps TV below acceptable limit for entire speed range. But this is a very costly approach. In this paper, the design of rubber TV damper for multi-cylinder engine was optimized to have lower TV characteristics. The optimized rubber damper has been developed with AEM - VAMAC™ grade rubber. This material provides advantages of better TV attenuation, higher thermal resistance, oil resistance higher durability and a much longer life than other rubber compositions. Besides rubber profile was also optimized to obtain higher slip torque. The TV amplitudes with existing rubber compound (EPDM -Ethylene Propylene Diene Monomer) were measured in the engine testbed.