Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/1035029
2019 BMW R 1250 GS FIRST IMPRESSION P80 T he goal of BMW Motorrad's team of engineers led by Ing. Nor- bert Klauer, its Head of Drive Train Development, to produce increased power and torque across the entire rev range of the new R 1250 GS en- gine, as well as enhanced rideability and greater refinement, coupled with reduced fuel consumption and emission levels, has resulted in the development of its innovative Shift- Cam Technology—the first time that a variable valve control system has ever been fitted to a BMW motorcycle. Although Ing. Klauer joined BMW Motorrad from its parent company's automobile division only five years ago, he insists that this all-new sys- tem owes nothing to the Vanos vari- able valve timing technology devel- oped 25 years ago for use on BMW cars, nor the Valvetronic variable valve lift system introduced in 2001, both of which were considered too bulky for motorcycle use. Instead, the R 1250 GS engine's cylinder heads feature the all-new, highly innovative ShiftCam system, which combines both variable valve timing and differ- ential valve lift, all in the same pack- age, as a means of optimizing cam timing and duration for what you're asking the engine to do. For part- throttle openings, or lower down in the rev range, the cam has a shorter lift and reduced duration, meaning the inlet valves are open less. But ask for more throttle or higher revs and the cam shifts sideways, bringing into play a higher lift, longer duration cam lobe, more suited to outright perfor- mance. This is achieved by having the inlet camshaft of each cylinder incor- porating two different cam profiles mounted side by side on the same shaft. One of these is a partial-load cam, which has been configured to deliver improved fuel consumption and refinement at part-throttle. The other is a full-load cam designed for enhanced output via more aggres- sive throttle openings, which delivers longer duration inlet valve openings. By means of an axial shift from side to side of each inlet camshaft, the paired inlet valves on each cylinder are activated via their finger followers by either the partial-load or the full- load cam, depending on engine rpm, gear selected, and throttle load. As the throttle opens wider via the throttle-grip, the electronic ac- tuator lifts a pin to lock into the inlet camshaft gate. The rotation of the camshaft then permits the pin to draw the camshaft sideways, to bring the more aggressive longer duration cam lobes into line with the valves. When the throttle is closed, the camshaft is pulled back across the cylinder head, and onto the less aggressive smaller profile cam employed for normal use. Either way, the change is practically instantaneous, taking just FIVE mil- liseconds to accomplish. That's less than the blink of an eye. Additionally, the variable con- figuration of the cam geometry also enables a variation in the inlet valves' stroke. While the full-load cam provides maximum valve stroke, the partial-load cam delivers reduced stroke. There is also a phased dif- ferential opening between the left and right-hand inlet valves in each cylinder, in terms of both stroke and angular position. This phased shift means that the two inlet valves are opened a differential amount in terms of lift—i.e. one more than the other—and on a time-staggered basis. This helps create additional swirl for the incoming charge of air and fuel, and thus greater agitation of the mixture as it flows into the combus- tion chamber. This results in both improved combustion—so, a bigger bang—as well as a more complete burning of the fuel, thus ensuring reduced emissions and a claimed up to four percent lower fuel consump- tion versus the smaller capacity, less powerful R 1200 GS. SHIFTCAM TECHNOLOGY EXPLAINED