Innovations for the BMW Motorrad Boxer Engine

Autoren

Dr.-Ing. Frank Schwarz, Dipl.-Ing. Norbert Klauer, Stefan Kallich, MSc.,
BMW Motorrad, München

Zusammenfassung

The BMW boxer engine is one of the bestselling motorcycle engines in the world and makes up to 40 % of BMW's market volume. This means that the boxer engine can be found in every 3rd BMW motorcycle sold today and is one of the most iconic motorcycle
engines. For the 2019 model year BMW made a major improvement to the K5x boxer engine during its second technical revision. The already sophisticated liquid cooled R1200 boxer engine with its outstanding performance, smoothness and drivability combined with a well-balanced power output was further improved.

The technical key point in this evolution from the R1200 to the R1250 engine is the integration of a shift cam system, which was especially developed and adopted for the use in motorcycles. BMW will actually be the only motorcycle manufacturer to include a shift cam system of this kind to a mass produced motorcycle.

The combination of the shift cam system and an increased engine displacement, in addition to a set of detailed optimizations of the gas exchange process responds to the continuously increasing demands by improving the torque levels, running smoothness
and overall performance. It results in an inspiring road performance and a widely usable engine speed range resulting in an unmatched high torque curve.

The shift cam system solved the target conflict between an optimized full load design of the gas exchange system and the requirements concerning combustion stability, lower engine raw emissions and reduced fuel consumption in part load conditions.

For this part load conditions the Shift cam was designed to strengthen turbulence and in-cylinder air flow, and to reduce the losses of the gas exchange process. Together with an optimized fuel mixture preparation the new R1250 engine is prepared to fulfill
the upcoming motorcycle emission levels, obligatory in 2020 for new models and 2021 for the complete fleet. A newly designed engine control unit with torque based functional structure was developed for better drivability and to integrate the shift cam system and improved functional diagnosis.

With the new BMW R 1250 models, the driving pleasure with the boxers engines - the core product of BMW Motorrad - is again on a new level. The new BMW boxer engine is the performer in every circumstance.

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