YZR-M1 Technical Guide - Motorcycle Race

The 2008 season was the second season of the MotoGP’s 800cc regulation. Through further maturation based on the results of the 2007 season, the YZR-M1 became the 2008 championship machine. Here we introduce details of what changes were made in the various components compared to the 2007 machine.

In 2007, Yamaha only won four of the 18 rounds (Round 2 – Spain GP; Round 6 – Italian GP; Round 9 – Netherlands GP; Round 14 – Portugal GP). In the ranking as well, Valentino Rossi could only rank 3rd on the year. Based on study of the reason for this poor performance, the following problems were identified.

1) Lack of engine performance and reliability	- Lack of acceleration performances / top speed - Overheating of coolant and oil
2) Fuel economy control	- Optimizing fuel/air mixture
3) Tire and chassis matching	- Front-rear grip balance (especially from entering a turn through the turning stage)

Based on the above three problems, the development aims for the 2008 YZR-M1 were “maximizing tire performance” and “strengthening engine output / improving fuel economy.” To achieve these aims, three specific things were undertaken to improve performance in the desired areas.

The following are the specific development measures undertaken for the chassis, engine and EMS.

- Review of dimensions
Based on reviews of dimensions including the caster angle, trail, rear arm length and rear suspension link, the wheelbase and the center of gravity were optimized to improve the front-rear weight distribution and improve cornering speed.

- Frame rigidity balance review
Compared to the 2007 model, the chassis’ longitudinal rigidity was increased by approx. 20% and the torsional rigidity by approx. 10%, while the lateral rigidity was reduced by 10% to increase flexibility for a further improvement in handling and stability from the point of entering a turn through the turning stage.

- Cooling effect
Cooling effect was increased by rectifying the flow of air through the inside of the cowling. This succeeded in lowering the coolant temperature by 10 ºC and the oil temperature by15 ºC, which helped improve the stability of the engine performance.

The biggest change that must be mentioned between the 2007 and 2008 machines was the adoption of pneumatic valves on the engine. In connection with this, the shapes of the intake/exhaust ports and the combustion chamber were also reviewed, with the result that a 12% increase in max. power output and 8% increase in max. torque were achieved compared to the 2007 machine. Also, it was possible to reduced the weight of the valve system by 40%. Furthermore, optimizing the pistons and links and a revision of the diameter of the crankshaft reduced surface abrasion, and adoption of a center oil feed system for internal lubrication, it was possible to reduce friction loss. The reductions were especially significant in for the valves, pistons and crankshaft and they contributed to and overall reduction in friction loss of 14% compared to the final spec of the 2007 machine.

These performance improvements produced increased top speed and improved fuel economy. In both cases, these elements are influenced by a variety of conditions such as track surface temperature and air temperature and weather, so it is difficult to provide a single performance figure, but on average increases of approximately 7 km/h in top speed and a 6% improvement in fuel economy were achieved.

The basic concept in the EMS development was to achieve real-time following capability to control machine behavior. Based on real-time data from sensors monitoring acceleration, suspension stroke and machine attitude (gyro sensors), etc., the EMS calculates the machine angle and tire traction (friction) capacity and determines the optimum engine torque to be applied. The “Estimated Grip Torque Limit” and “Estimated Wheelie Torque Limit” derived from these calculations are then used to modify the rider’s throttle action to achieve traction control and wheelie control. The resulting improvements in the throttle control system have served to reduce wheelies and rear wheel spinning and helped achieve more stable machine control.

The above-mentioned improvements to the 2008 spec YZR-M1 helped achieve the initial development goals of “maximizing tire performance” and “strengthening engine output / improving fuel economy.”
The thorough review and revision of the chassis dimensions made it possible to set up the machine for maximized tire performance in much shorter time than before, while the improvements to the EMS helped reduce wheelies and wheel spinning plus aiding in the maximizing of tire performance.
With regard to the goals of strengthening engine output and improving fuel economy, actual improvements of 12% in engine performance and 6% in fuel economy were achieved.
With these improvements, Rossi was able to win nine of the 18 rounds of the season in winning the 2008 MotoGP rider championship. And thanks to the performance of 2008 YZR-M1 and the riders and teams that used it, Yamaha also won the manufacturer’s title and the team title (Fiat Yamaha Team) to claim the coveted MotoGP “Triple Crown” in 2008.

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