There is a need to develop cold-engine test stands for use in diagnosing cylinder faults and measuring gear noise given the new quieter fuel injection systems in modern engines. When engines run hot, these characteristics are not easily measured. By running the unfired cold-engine as a load using an electric motor and driveline, torque measurements can be used to diagnose assembly faults, damage and noise characteristics. In this paper, two cold-engine test stand drivelines are considered. Both stands experience large torsional vibrations excited by the various engine harmonics. Engine fault diagnosis becomes a challenge when these torsional vibrations degrade the measured torque signals. To solve this problem of torsional vibrations, an engine test stand model is developed to understand the system dynamics and analyze the free and forced response characteristics of the system. The model is used to predict the impact of the changes made to the test stand driveline and the trends observed in the simulation results are compared with experimental results for model validation. It is shown that based on model sensitivity analysis the changes made to the driveline parameters help to reduce the amplitude of the driveline resonances considerably. The developed model can be used to design a cold test stand for production diagnostics.

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