Honda’s Second-Generation Motorcycle DCT
Fresh from the positive reception accorded to the dual clutch transmission on last year’s VRF1200 supersports motorcycle, Honda has developed a second-generation DCT system aimed at a very different category of bike. With the company’s market research showing that a substantial proportion of riders worldwide want to use their bikes on a daily basis, rather than occasional fun trips on supersports machines, Honda set about producing an easy-to-ride bike with good torque at low rpm, aimed at what it describes as “discerning adults of a certain age.”
For this new type of motorcycle, which combines the advantages of both a traditional bike and a maxi scooter, Honda designed a clean sheet of paper parallel twin engine of 670 cc, along with a new take on a two-wheeler DCT. The result is a machine which is expected to appeal not just to motorcycle and scooter enthusiasts but to car drivers too, with a fuel consumption saving of 40 percent compared with other models in the same capacity class.
Labeled Integra, the new Honda bike is designed to suit a new generation of motorcyclists who value ease of everyday riding over ultimate speed, but who do not want to compromise on handling or responsiveness when speeds increase. The machine’s mechanical layout is designed to enable maximum comfort and luggage storage, and the large wheel configuration – in contrast to small-wheeled maxi scooters − allows the use of panniers for secure stowage.
Automatic transmissions, says Honda, will become increasingly popular on larger motorcycles as greater numbers of older people use them as recreational vehicles. The high-efficiency engines consume less fuel, allowing for a smaller fuel tank and, in turn, permitting a lower seat height and greater storage space.
The new engine, shown here with manual transmission, was developed in response to research which showed that 90 percent of large motorcycle use was at speeds under 140 km/h, and that engine revs stayed under 6000 rpm for 80 percent of riding time. The liquid-cooled two-cylinder engine is sloped forward at 62 degrees and has a 270 degree phased crank to produce uneven firing and an evocative throbbing exhaust sound.
The crankshaft undergoes an innovative 90 degree twist between lobes during manufacture, saving weight over a forged or machined component. The development team’s target was to improve fuel efficiency by 50 percent compared with conventional engines in the same displacement class.
The second-generation dual clutch transmission for motorcycles is simpler, more compact and less expensive to manufacture than the original on the VFR1200F. A spur gear sandwiched between the two equal-sized clutches takes the primary drive from the crankshaft, in a manner similar to the arrangement on the company’s quad bikes. The even-numbered ratios (blue) are controlled by the inner clutch, with the outer clutch (red) handling launch and the odd-numbered ratios.
The clutch cover incorporates a patented network of passages for oil supply, and the system is calibrated for the lower shift-shock levels associated with lower engine rpm and reduced machine weight. The hydraulic circuit is shortened by 40 percent, providing greater responsiveness and quicker changes.
New, too, is a learning function incorporated in the control software. It enables the machine to distinguish between gentle running on straight roads and sporty driving on mountain routes, and adjusts the gearshift strategy accordingly. As with DCTs fitted to cars, the transmission returns to automatic operation under certain conditions, and after a certain length of time after the rider has overridden it with a manual change.
Motorcycle specialists expect that the DCT transmission in the Integra will offer buyers a key advantage in the growing market for convenient, yet also enjoyable, two-wheelers. It promises to combine the “twist and go” ease of riding of a CVT-transmission scooter with the ability to provide a much more responsive and sporty riding experience. The positive, quick-shifting dual clutch gearbox with its real gears gives a gearshift feel that is on par with a manual.
Two other motorcycles based on this engine and, in all likelihood, this new transmission, are promised by Honda this autumn. While the company has not provided any details, the additional production volume has the potential to draw DCT biking out of its niche segment and into the mainstream. The prospect of lowered manufacturing costs further enhance the appeal of the system.
Story Filed: 11/29/2011
By Tony Lewin, managing editor DCTfacts.com