BMW's new six-cylinder engine

BMW had developed a straight-six engine for a motorcycle platform, attempting to make meaningful inroads into a genre that has never really gained massive traction – either in volume production or racing.

To makes its public debut, BMW has chosen to marry the straight-six to the muscular ‘Concept 6’ café racer, but the company has confirmed the powerplant will make its first ‘real’ appearance in a 2010 luxury tourer, further expanding the K-series range.

Competition for the new bike will include the Honda Goldwing (which has a flat-six engine), Victory Vision and Harley-Davidson Ultra-Glide.

BMW claims the engine is 100mm slimmer than all former straight-six production engines, which has been achieved by producing an oversquare bore – that is a long-stroke design. That cuts down the gap between cylinders, while all the electrical ancillaries and drive components have found sanctuary behind the crankshaft in the open space above the transmission.

The cylinders are tilted forward by 55 degrees, which BMW claims maximises centre of gravity while delivering precise feedback from the front end. The lean angle also provides extra space for the intake manifold.

In Concept 6, there is a dry-sump lubrication, which keeps the crankcase low and flat – again in deference to keeping the centre of gravity as low as possible. One would presume the dry sump would continue in a volume production machine.

BMW hasn’t given a capacity for the straight-six, but it does say it’s “no less than 1.6lt” (1600cc).

Peak power is likely to be in the zone currently occupied by the K 1300 range (around 175hp) at around 9000rpm, but it then claims torque “will be right at the top of the range, even in comparison with the largest motorcycle engines”.

One would assume that would put the straight-six in the same orbit as, say the upcoming Triumph Rocket III Roadster streetfighter, which produces a mighty 220Nm.

But then the BMW literature goes onto say that the straight-six will offer 130Nm from just 2000rpm – still respectable, but hardly at the pointy end of the torque stakes.

We shall wait and see what the LT brings us in 2010.