BMW Developing Adaptive Cooling for Motorcycles

Admin · February 17, 2023

The 2024 BMW X5, like many other models in its range, has sliding shutters hidden behind the kidney-shaped grille that open and close depending on the car’s requirement for airflow to the radiator. (BMW/)

Look at the vast kidney-shaped grille on many modern BMW cars and you might notice that it appears to be a blanked-off dummy rather than a real air intake. That’s actually because in the pursuit of better aerodynamics BMW employs shutters that close off the main grilles on several models when maximum cooling isn’t required—and now the same idea is being developed for motorcycles.

A BMW patent application has revealed what the firm dryly calls a “tilting vehicle having a cooling arrangement with a movable air-guiding device.” Illustrations clearly show a shutter-style system arranged in front of the radiator of a liquid-cooled boxer twin. Just like the cars that use a similar system, the idea is to allow enough cooling to satisfy a high-performance engine working at peak load, but also to provide improved aerodynamics when the engine isn’t being stressed and pumping out as much heat.

The patent explains the problem, saying that in pursuit of cooling efficiency, motorcycle radiators are mounted where they’re exposed to as much airflow as possible, inevitably creating a substantial aerodynamic obstacle. The issue is worsened by the fact that the cooling system has to be designed to cope with extremes of weather or performance, quite unlike those that will be met on a day-to-day basis. In the words of BMW’s patent application: “the cooling arrangement is usually designed on the basis of the greatest power requirement to be expected, which can occur in the case of extreme operating conditions. In everyday situations with lower performance requirements for the cooling arrangement, this is correspondingly ‘oversized.’”

Unlike its cars in which sliding shutters block off the airflow behind the grille, BMW’s idea for the motorcycle equivalent would have louvers that would open and close and stop air from passing through the radiator, improving aerodynamics. (BMW/)

While the excess cooling ability of a conventional bike’s radiator is solved via the use of a thermostat to regulate the flow of coolant into the radiator, it doesn’t reduce the aerodynamic drag and resulting inefficiency caused by the presence of the radiator itself. That’s where the idea of active shutters comes into play. Just like the system already in use on BMW’s cars, the firm’s patent suggests employing a venetian blind–style system of air guides in front of the radiator, operated in unison by a single servo to open or close the intake depending on the cooling requirements.

Depending on the angle and position of the radiator and these shutters—and you can be sure the final version will be much more subtle than the simplistic illustrations in BMW’s patent, seen here—the aerodynamic benefits promise to be substantial. With the shutters closed, either fully or partially, air is redirected around the radiator rather than through it, cutting drag and improving efficiency.

Although we can’t draw too many conclusions from the drawings in the patent, the decision to illustrate the idea on a GS-style boxer-engined adventure bike could be significant, since there’s a new R 1300 GS boxer under development and expected to be launched this year for the 2024 model range. Since BMW already mass-produces an active grille system for use in millions of cars, translating it to motorcycles shouldn’t prove to be a hugely taxing task if the benefits prove to be as significant as the patent application suggests.

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