In normal IC engine operation 1st compression ring sustains thermal loads effectively. At large radial clearance in low-speed engine start up it has to act as effective seal against thermal loading. Absence of elastohydrodynamic lubricating (EHL) film and secondary displacements expose the ring to adhesive wear in initial engine start up. Isothermal hydrodynamic and EHL models of parabolic-faced ring are developed numerically after incorporating secondary dynamics of piston assembly at a low engine start up speed. Reynolds equation is solved to generate hydrodynamic pressures and film profiles in 4-stroke cycle. In EHL model inverse solution technique and elastic displacements of ring and liner are employed to generate pressures and film profiles. The simulation results suggest that a large ring-to-bore clearance increases eccentricity and affects EHL of 1st compression ring when a low-viscosity grade oil is used in initial engine start up.

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