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The reduction of oil demand for automotive engines has been driven recently by the need to reduce oil pump capacity so that benefits from having a smaller size, including a reduction in power loss and CO₂ emissions. Crankshaft bearings are generally attributed to be the largest consumers, main bearings in particular since the supply pressure in the upper bearing shell oil groove over a large arc (circumferentially) coincides with high average clearance. Measurements of oil flow indicate that the main bearing groove is significant and there is a trade-off between lower oil flow and higher bearing temperatures. All solutions must ensure that the oil supply to the big-end bearings via crank drillings is not compromised. Numerical simulation tools can be used to predict and optimize the total oil flow required by the engine lubrication system. In this work, the Elasto-Hydrodynamics Simulation (EHL) was used to analyze the oil flow required by the crankshaft main bearings.

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.