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The present study looks into different possibilities for tribological optimization of the piston/bore system in heavy duty diesel engines. Both component rig tests and numerical simulations are used to understand the roles of surface specifications, ring pack, and lubricant in the piston/bore tribology. Run-in dynamics, friction, wear and combustion chamber sealing are considered. The performance of cylinder liners produced using a conventional plateau honing technology and a novel mechanochemical surface finishing process - ANS Triboconditioning® - is compared and the importance of in-design “pairing” of low-viscosity motor oils with the ring pack and the cylinder bore characteristics in order to achieve maximum improvement in fuel economy without sacrificing the endurance highlighted. A special emphasis is made on studying morphological changes in the cylinder bore surface during the honing, run-in and Triboconditioning® processes.

The gas that flows from the combustion chamber to crankcase of internal combustion engines (“Blow-By”) and the reverse flow (“Blow-Back”) have detrimental effects in the engine power, pollutant emissions and lubricant degradation. A main factor to control this flow is the first piston ring gap. The influence of the area defined by the gap, specially of the chamfer at end gap, is analyzed by computer simulation and dynamometer tests. An unusual type of piston ring contact face coating at end gap, allows a reduction of up to 50% in the ring gap area and engine Blow-By.