Isolation of Engine Vibrations from 3 Cylinder Engines on Off-Highway Machines

The new Stage 5 emission regulation requires several changes on engines as well as design and development of new auxiliary systems. These changes affected the engine dynamics and NVH characteristics. These changes are validated for various operating conditions on engine test cell in a controlled environment where engine is mounted on test cell with dyno. Further, this engine will be used by other machine forms, hence NVH performance needs to be evaluated for all the applications. Isolation of three-cylinder engines is challenging since it has to deal with inherent imbalance forces while providing the isolation to meet the durability requirements of heavy applications from off highway machines. This paper covers the methods used for verification of engine isolation performance. NVH tests are conducted for integration of three-cylinder engine with roadbuilding machine. An analytical model is developed to identify rigid body modes and mount transmissibility. Results from this analytical model were verified with a physical experimental modal analysis. Vibration transmissibility at each mount is measured to ensure sufficient vibration attenuation. Vibration levels on machine frame and cab seat are evaluated in various operating conditions. These evaluations helped to select suitable isolators for machine NVH performance.