Twin-cylinder boxer engine 1250 cc (air-liquid-cooled) with BMW ShiftCam
A new generation of twin-cylinder Boxer engine needs a new technology: the BMW ShiftCam. The result is more power over the entire – particularly in the lower – engine speed range, increased energy efficiency, hence a very smooth-running engine. With the enhanced twin-cylinder boxer engine, the traditional design reaches a new level of performance and torque. The new power train thrills with power delivery and a particularly pleasant sound.
The core
The core
For the first time, BMW ShiftCam technology is used in a BMW Motorrad series engine – a technique for varying the valve timing and valve lift on the intake side. At the heart of this technology is a one-piece camshaft, which has a two cam pair per actuated valve: a part-load and a full-load cam, each with different and optimally designed cam geometry.
Ingenious interaction
Ingenious interaction
While the part-load cam was developed for consumption optimization and smooth running, the full-load cam is optimized for performance. Using an axial shift of the intake camshaft, the inlet valves are actuated depending on engine speed and load intensity - either with the part-load or full cam pair. This displacement – and thus the use of part-load or full-load cam – is initiated by a shift gate on the camshaft and an electromechanical actuator.
Efficient combustion
With the different design of the cam geometry, there is also a variation of the inlet valve. While the full-load cam provides the maximum valve lift, a reduced valve lift is available with the part-load cam. In the part-load cam, the inlet cams for the left and right inlet valves differ in stroke and angular position. This phase shift causes a time-delayed and varyingly wide opening of the two inlet valves. The advantage of this phase shift, is that the fuel-air mixture flowing into the combustion chamber is more strongly swirled and effectively combusted – which, in the end, means optimal use of fuel.
Optimum oil supply, optimum fuel injectors
Optimum oil supply, optimum fuel injectors
If you increase power and torque, you must also optimize the oil supply. The two pistons are cooled from the bottom using oil spray, and the lubrication system is equipped with a variable oil intake. The developers ensured optimum oil supply for all riding conditions and riding modes. Also new is the BMS-O digital engine control. Its main features are fully sequential injection, compact layout and low weight. The mixture preparation is taken over by an electronic fuel injection over throttle body with 52mm opening width. New dual-jet injectors support an even higher running rate and improved emission values.
Intermediate shaft compensates for vibrations
Intermediate shaft compensates for vibrations
As with the previous twin-cylinder Boxer engine, a balance shaft running with crankshaft speed eliminates unwanted vibrations in the new power train. The balance shaft is designed as a hollow intermediate shaft, in which the clutch shaft runs simultaneously. This means the new drive also runs with low vibration over the entire engine speed range. The robust, twin-cylinder Boxer engine-typical basic characteristics are still maintained, while the performance data testifies to its power: In the new generation, the twin-cylinder boxer engine has a peak output of 136 hp and a capacity of 1,254 cc.
