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This work presents an experimental study to analyze the influence of surface finishing on engine journal bearing performance. Bimetallic bearings were manufactured with two bored finishings, one called conventional and another microprofiled. Microprofiled bearings have a potential advantage due to the higher conformability of these parts under the engine operational conditions. Bench tests and engine test were conducted in order to check the loading carrying capacity (LCC) until seizure occurrence; the temperature was evaluated at the steel back of the tested parts. Surface of the parts was evaluated after the tests. The results showed that microprofiled bearings presented slightly lower temperature at steel back during the bench tests than the conventional bearings. The loading carrying capacity for both parts was similar, due to the relatively low speed test.

This paper presents some definitions about the bore surface finishing and its influence on the piston rings performance. The surface finishing of a cylinder is in most of cases obtained by a machining process called honing. In recent years, developments and innovations to the honing process have been implemented. These new surface finishings are being implemented in order to improve the working condition of the system. Some of these developments are presented. This paper also presents some benchmarking of bore finishing for SI engines and case studies showing the influence of the surface finishing on the rings performance, regarding wear, friction and lube oil consumption. The results showed that smoother bore surfaces presented lower friction coefficient and also lower wear on the rings and bores. Finally a recommendation for bore finishing and its evaluation for modern SI engines is given.

The market has recently required the bearings to operate under intermittent or occasionally boundary lubrication conditions through requirements guided basically by CO₂ reduction: flex-fueled engines, stop-start operation, specification of low viscosity oils, extension of high speed regimes with low stiffness conrods and crankshafts. The sensitivity of the oil film rupture, higher loads and the robustness of operation required the development of low friction coatings or overlays with improved wear resistance. MAHLE response to these requirements has been addressed through a newly developed product assigned as polymer-coated bearing. The polymeric overlay has a proprietary low friction solid blend and it is sprayed onto premium bimetallic bearings. In this paper it is shown that these bearings run at lower temperature, with lower friction and can support higher loads than the conventional bimetallic bearing.