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Flat twin engine

More powerful, more refined and more economical in fuel consumption: BMW Motorrad presents the latest generation of the flat twin "boxer" engine so characteristic of the brand. With its air/oil cooling and 4-valve technology, the new flat twin engine is identical in its design principle to the traditional BMW Motorrad 2-cylinder power units, but nonetheless it is in fact a completely newly developed engine. All performance-related components have been revised. For example, with 73 rather than 70.5 millimetres stroke a new and lighter crankshaft increases capacity to 1170 cc. The increase in output and torque is equally impressive: depending on the model up to 81 kW (110 bhp) and 115 Nm at 5500 rpm.

Other components contributing to this impressive increase in power in the current boxer engine are the larger valves, optimised intake and outlet channels, a higher compression (R 1200 GS 11.0:1; R 1200 RT/ST 12.0:1) and the significantly enlarged airbox, now with a volume of 9 litres. The result is supreme character which convincingly demonstrates its superiority from the very lowest engine speeds - a perfect example of outstanding dynamic performance and free revving.

A key development goal in the new flat twin engine was also the further improvement of running smoothness. Thus the new engine - for the first time in the history of BMW Motorrad flat twin engines - now has a balancing shaft. So as to save space, it runs inside the hollow auxiliary shaft for the camshaft drive and thus ensures optimum running smoothness and silken-soft pulling power across the entire engine speed range, though without diluting the essential character of the twin-cylinder engine. The only exception here: in the flat twin in the HP models, the balancing shaft is omitted for weight reasons.

The new flat twin is bigger on capacity and output than its predecessor, yet it weighs less - in spite of the additional balancing shaft. Consistent lightweight construction has reduced its weight by a total of 3 kilograms, achieved by state-of-the-art development methods and innovative die-cast techniques. One example of many: the crankcase is now significantly more rigid and stable, yet the entire component is 1.4 kilos lighter. And the lightweight principle has been consistently applied inside the engine too: for example the new crankshaft saves a whole kilogram.

Finally, a world first in motorcycle construction in the current boxer engine is the knock control function. Here, sensors register every uncontrolled combustion - such as might occur due to poor fuel quality for example. The engine management system then adjusts the ignition timing towards "late". This highly compressed engine can thus make do with regular fuel if necessary. The latest development stage of the engine electronic system BMS-K and the modified dual ignition reduce fuel consumption by some 8% - in spite of the higher engine performance. There are also two oxygen sensors which combine with the closed-loop three-way catalytic converter to ensure minimum pollutant emissions in line with the currently valid exhaust emission norm EU 3.

The new flat twin engine from BMW Motorrad is the best "boxer" ever. More powerful and more dynamic, it continues to arouse emotions a motorcyclist can't fail to resist - just as it has been doing for eighty years.