On the basis of the concept of new Gold Wing, the new horizontally-opposed six-cylinder power unit was developed with the theme “smooth yet aggressive at times, light weight and compact flat-six power unit.” To achieve weight reduction and compactness of the power unit, the materials and the shapes of the crankshaft and the connecting rods were redesigned. To realize lightweight and compact power unit, the Unicam valve train having finger follower rocker arms for the intake valves and the single throttle body were applied. To enhance combustion efficiency, the combustion chamber was changed from bathtub type for two valves, to the pent roof type for four valves. In addition, the compression ratio was increased and the intake ports were applied with a shape generating a strong tumbling of intake air. To enhance maneuvering qualities, which was derived from the set concept of the developed motorcycle, a throttle-by-wire system was adopted. To the drive system of the Integrated Starter Generator, a damper of revised configuration and a rubber coupling were implemented and the requirements for tranquil riding were fulfilled. A comfortable exhaust sound was also provided by reassessing the design of the exhaust system. With all the measures mentioned above, weight reduction, together with downsizing, was successfully achieved by 7.1 kg for the DCT equipped model and by 9.5 kg for the MT equipped model compared to the previous model. Furthermore, the peak output power was increased by 6 kW and, yet, the fuel economy was improved by 24% (in the case of the model sold in Japanese market) in the WMTC mode (class 3-2). As mentioned above, the enjoyably deep and pulsated exhaust sound was also achieved while offering the mild and high quality sounds of mechanical operations.
Article of Honda R&D Technical Review Vol.30 No.2 (16 - 30)