The real measure of machine performance is not in the spec numbers but in the performance the rider can get out of the machine. The aim is rider-machine unity. That is where the big potential lies.
"Drivability" that can't be measured in machine specs
Yamaha Motor thinks of an engine as not only the power source but also as a component of the machine that can contribute to its running performance and agility-in other words the machine's "drivability." Building that kind of engine can be called a process of building in "hidden specs" that the rider feels but don't appear on the specification sheet.
There are numerous aspects of an engine that affect a machine's drivability, and one that Yamaha pays special attention to is the "crank web." Making the crank web lighter increases the machine's pick-up, but if it is too light, it detracts from the machine's feeling of stability. So, both the shape and the mass of the crank web have a big influence. That is why Yamaha engineers devote great efforts to adjust the shape and weight in increments of one millimeter or one gram and verify the effect in test after test by our expert test riders in order to hone the performance and movement of the machine to a ride that "feels right". Because the human perceptions of experienced test riders are the final test, Yamaha snowmobiles have performance that moves the body and stirs the soul of the rider. The surge of acceleration the rider feels with a Yamaha is something beyond raw engine power, and the feeling of stability in the handling makes you want to ride on and on.
Design and engineering expertise to maximize both stability and handling
The excitement of the ride is actually supported by a finely tuned harmony of stability and handling characteristics based in areas like frame rigidity balance and the un-sprung components. With the un-sprung components, for example, there are a number of options that can be used to increase stability, such as adjusting the ski stance, lengthening the track or lowering the center of gravity. To improve handling response, the shape of the skis can be adjusted, the track can be shortened and the center of gravity can be raised to enable quicker cornering characteristics. As this shows, stability and handling performance are diametrically opposed qualities by nature.
At Yamaha, however, our aim is to achieve high levels of both stability and handling. To do this, Yamaha engineers first use simulation analysis to develop a prototype with the best potential and then turn it over to the test riders to begin a process of fine-tuning the stability and handling based on their highly refined human perceptions. Since there is such a large number of parts and components involved that affect stability and handling, and by taking into consideration the sizes and shapes of each of these, the possibilities for refinement expand greatly. That is where the test riders use their finely honed senses and the design engineers use their knowledge and experience to make adjustment after adjustment to develop the best possible package. It is this development process that gives Yamaha snowmobiles the reassuring stability and very linear handling response that lets the rider get the fullest possible enjoyment out of the ride.
Handling performance that has both lightness and stability
The key factors for enjoying agile cornering are linear handling performance in response to the combined steering action and shifting of body weight and a feeling of good machine stability. As key elements in achieving this kind of handling performance, Yamaha Motor focused on the two main components involved in the machine's contact with the snow surface: the skis and the front suspension.
In our quest for skis that provide outstanding running performance with minimum sinking into the snow and lateral drift, Yamaha Motor has independently developed a number of skis to fit the specific needs of our different models. For the front suspension we chose the double wishbone type because of the greater freedom it enables in setting the geometry. The suspensions are designed to keep the skis firmly in contact with the snow, and setting variations are made to meet the specific character of each model. Also, electronic power steering (EPS) has been adopted as a feature that controls and adjusts the reactive forces from the snow surface while supporting the steering action of the rider. This combines with the effects of the suspension and skis to further boost the light and stable handling performance.
"snow surface contact" as a key to high performance
The running performance of a snowmobile involves of a number of factors, such as performance over bumps and ruts, performance in fresh snow, steering performance and power development characteristics. At Yamaha we don't think of performance simply in terms of data based on measurements of time, distance and speed. In order to achieve performance that is fun, Yamaha works to build in machine dynamics that give the rider optimum input to enable him/her to "feel" the snow surface as they ride.
During the riding tests, the development team works to achieve a state where the machine gives the rider a good feeling of the snow surface when the machine weight is on one ski during a turn. It is something close to the image of a skier feeling the changing conditions of the snow surface through the subtle movements of the skis as they ski down a slope. The performance of the suspension and the numerous other components involved are honed to achieve a feeling as close as possible to direct human perceptions. That reliable input from the snow surface gives the rider a sense of confidence and makes riding more fun. That is what makes for outstanding running performance.
The benefit of the "rider-forward position" for greater rider freedom
Yamaha Motor describes its ideal riding position in the words "rider-forward position." But the meaning of these words in our development work is slightly different from simply positioning the rider forward on the machine.
The center of gravity of the machine is designed to be roughly where the engine is mounted. This is because a machine has better response if the center of gravity is at the middle of the machine. And positioning the rider forward leaning close to the front of the engine helps create a stronger feeling of rider-machine unity and lets the rider bring out the inherent performance potential of the machine more directly.
At the same time, a snowmobile is a 'rider active' machine. The actions of the rider, like the aggressive shifting of body weight through the turns, add variation that expands the performance potential. The shape of the seat, the position of the handlebars, step-board and their angles and shapes and heights are all designed with millimeter precision to enable the greatest possible freedom of motion for the rider to shift body weight at will.
Yamaha Motor's formula of "rider-forward position = greater freedom of riding position" is intended as a message from Yamaha that we want riders to thoroughly enjoy their riding in a wide range of environments and conditions.