MotoGP » 19 November 2006
Evolution of the YZR-M1 - part one.
Tsuji then returned to the three main development objectives - chassis, engine and engine management system - describing the particular attributes necessary for success in each area (top picture, 'Development objectives of the YZR-M1').
"Firstly the chassis, the YZR-M1's biggest feature is its short wheel base combined with a long swing arm. This is the essence of the YZR-M1 concept. To enhance this character, we evolved the frame, aerodynamics and centralisation of mass," said the Japanese.
"The engine and the engine management system are difficult to separate. A short wheel base can sometimes be a disadvantage in terms of ridability. For example, it is easy to wheelie on acceleration and can be unstable when braking. The engine must have the highest power possible, but at the same time it needs to stay controllable. From 2005, we also focused our development on fuel economy.
"It is also very important to remember that we spend a lot of time making sure that these [engine management] systems are working correctly," he stressed. "With the important sensors, we are using double, so even if one sensor breaks the system will continue to work by using the other sensor. If both sensors break, the bike will stop gradually, but fortunately we have never experienced this situation."
Looking specifically at the M1 frame (middle picture, 'Evolution of frame'), Tsuji revealed how and why Yamaha had kept vertical stiffness, while reducing lateral stiffness.
"The frame determines the bike's character," he said, "Generally the frame is evaluated by the stiffness. The YZR-M1 frame is designed to keep vertical stiffness and reduce lateral stiffness and torsion.
"This is because the bike's suspension only moves in a vertical direction - up and down - so when the bike is banked over [during cornering], the frame must also act as suspension. That is why we focus very much on this element with many tools and simulations.
"For 2005, we removed the cross member. This reduced lateral and torsion stiffness and gave a lot of improvement for agility and stability. At the same time we designed the air-intake passage through the head pipe, this way the frame helped improve the engine performance. These ideas will continue to have an effect in the future."
In terms of aerodynamics, Tsuji explained the conflicting interests of straight-line performance and cross wind stability (middle picture, 'Evolution of aerodynamics').
"Aerodynamics is one of the important things for the bike, so we spent a lot of time on development," he declared. "To put it simply, to have more speed and acceleration, we need to minimise the front view of CDA. CDA means drag co-efficient multiplied by frontal area.
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