Recently two-mass flywheels have adopted in various types of engines to decrease torsional engine vibrations. A two-mass flywheel has a resonance frequency below the idle speed. Thus, it must be provided with an energy dissipating mechanism to avoid a resonance problem. Consequently, flywheel's damping effectiveness at practical engine speeds is decreased because the energy dissipating mechanism restricts relative displacement of the two-mass flywheel. In this work, a new prototype two-mass flywheel was evaluated and found to be effective in improving two important qualities of such devices; (1) its ability to decrease torsional vibrations (2) its ability to avoid resonance problems during engine startup.