Eleven years ago, BMW Motorrad introduced a motorcycle with a straight-six across the frame engine. But it wasn’t the K 1600 GT; it was its daddy, the unimaginatively named Concept6 which never saw a factory or showroom floor. Its purpose, apparently, was purely to introduce the engine – in a motorcycle that did not resemble the final product in any other way. The company even said as much during the introduction of the prototype, or should I write ‘prototype’?
I have been in this business for fifty years, and I have never seen any other motorcycle manufacturer pull a trick like this. So much for the allegedly conservative Bavarians. It must have cost a fortune to create Concept6. As far as I could tell, this was not the old wooden-parts-painted-to-look-like-metal cut-cost concept. It looked ready to go. Then again, we never saw riding shots of the bike or heard it fired up, so it may not have been a runner.
Concept6 was far from a sterile design exercise. The name might have been – well, was – dull, but the motorcycle was anything but. Taking some cues from the then-new S 1000 RR, its styling was almost a typical David Robb design.
“Supremacy and dynamism are also borne out clearly by the thrilling design of the Concept6 and, as usual, this project from BMW Motorrad is more than ‘just’ the attempt to develop a motorcycle of a kind never seen before,” said the factory. Umm, okay, so the point of the design was to “focus[ed] yet again on technical function and quality and, in particular, the emotional element bringing together man and machine.” Yes. Fine. And? “A motorcycle must not only follow the laws of functionality, but also arouse emotion in all its facets. In a nutshell, therefore, the machine must be simply thrilling.”
All sounds pretty thrilling, doesn’t it, although you would think that that would have been the point with every bike designed by BMW. But never mind the fluff. The point of this bike was always the engine.
BMW has a long record of in-line sixes, but they have been in cars. “The typical sound of a straight-six almost like a turbine is absolutely incomparable, with straight-six power units at BMW having stood for fascinating engine technology in BMW cars for more than seven decades” said the factory at the introduction of the Concept6.
BMW was all too aware of the difficulty posed by the basic problem: size. “Inventive engineers have also tried time and again to offer the enthusiast the thrilling concept of a straight-six power unit. But while a few engines in straight-six configuration have indeed been fitted in motorcycles both lengthwise and crosswise, the straight-six has never really made a genuine breakthrough,” they said. “Depending on the way the engine was fitted, six cylinders in-line inevitably made the engine either very long or very wide, creating disadvantages in terms of the running gear, weight distribution, and the centre of gravity. A further drawback was much higher engine weight usually setting off the benefits of extra engine power.”
But the factory had an enormous amount of experience with sixes, and as a result the new engine offers an extremely compact form and configuration. The power unit is approximately 100 mm or 4 inches slimmer than any former straight-six production engine and only a little wider than a large-capacity straight-four designed with conventional technology.
Advanced technology lightweight construction in all possible areas makes the engine relatively light from the outset with features like the two hollow-drilled camshafts and the light connecting rods. The perfect compensation of masses ensured by the configuration of the engine avoids the need for a balance shaft, which again means lower weight as well as running smoothness.
The straight-six has its cylinders tilted to the front by 55 degrees, like the straight four in the K 1300s. This means a low centre of gravity and good weight balance to help provide precise and clear feedback. The engine comes with dry sump lubrication, which offers reliability even under extreme conditions, and keeps the crankcase low and flat. That allows the engine to be fitted lower down and concentrates mass around the centre of gravity. Doing without an oil sump, the engine may be positioned far lower than on a conventional layout.
The new engine offered 130Nm or 96lb-ft of torque from just 2000 rpm while also revving up to almost 9000rpm. “Fuel consumption of this six-cylinder naturally equipped with a fully controlled catalytic converter is lower than on a comparable four-cylinder under normal touring conditions. The use of E-gas technology (ride-by-wire) then offers further potentials for enhanced fuel economy and riding dynamics throughout a wide range of different riding modes and conditions,” says BMW.
So does that mean we will ever see a performance monster like daddy Concept6 on the road? When announcing the bike in 2009, BMW said that “the first model to be introduced [with the six-cylinder engine] will be an innovative and luxurious BMW touring machine.” Okay, we have seen that, and not only in one bike. The engine’s power and performance characteristics also qualified “the engine of the Concept6 as the ideal power unit for a wide range of different motorcycles.” That suggests pretty clearly that other models outside the GT range are in the pipeline — or were at the time.
It’s been nigh on a dozen years, Munich. Daddy must be getting restless.
Footnote: With the advent of Euro 5, BMW has announced that all of the sixes will go into limbo. Will they be back? As I write, I do not know.
(Photos BMW Motorrad)