The investigations and developments described in this article substantiate the potential for reduction of fuel consumption and the general feasibility of a roller bearing crank train in an internal combustion engine. An improvement of fuel consumption of 5.4% (NEDC) resulting from reduced friction was proven on the basis of a given 1.6L 4-cylinder plain bearing engine converted to roller bearings. By means of subsequent calculations and simulations, the parameters for optimisation of the engine acoustics and durability were identified. Based on these findings, an advanced test engine was set up. Measurements with this generation 2 roller bearing engine demonstrate the expected significant improvement of NVH behaviour. In parallel to the investigations with the generation 2 prototype which had to be a compromise with regard to robustness due to the requirement for a quickly realisable and feasible application, a completely new roller bearing bottom-end concept (generation 3) was developed. This new design meets the main requirements of optimal roller bearings while also taking the boundary conditions for high-volume production into account. The essential attributes of this generation 3 roller bearing crank train concept are the single-piece conrod and main-bearing pedestals which are threaded onto a crankshaft with detachable counterweights. The extra cost of EUR 50.- to 70.- for these roller bearing engine concepts is on a low level compared to the achieved reduction in fuel consumption.

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