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A ring pack friction model has been developed based on the mixed lubrication concept to investigate the effects of ring surface topology on ring/liner interfacial frictions. The simulated friction results were verified by using the moving liner test rig and good correlations were established. The developed model was then extended to simulate the ring pack frictions under engine firing conditions. Surface roughness pattern oriented in the transverse, isotropic, and longitudinal directions were analyzed. The results indicate that the influence of surface pattern on ring pack friction is very substantial. A reduction of 9 percent of the ring pack friction is observed simply due to the surface pattern change. Friction reduction is a result from an increase in film thickness. This also helps to decrease the friction spikes near the dead centers and reduce ring wear. An increase in surface roughness magnitude significantly increases the ring pack friction.

Only a limited understanding of the oil consumption mechanism appears to exist, especially oil consumption under transient engine operating conditions. This is probably due to the difficulty in engine instrumentation for measuring not only oil consumption, but also for measuring the associated in-cylinder variables. Because of this difficulty, a relatively large number of experiments and tests are often necessary for the development of each engine design in order to achieve the target oil consumption that meets the requirements for particulate emissions standards, oil economy, and engine reliability and durability. Increased understanding and logical approaches are believed to be necessary in developing the oil-consumption reduction technology that effectively and efficiently accomplishes the tasks of low oil-consumption engine development.