Diasil Development background

In general, motorcycle engines run at high rpm (10,000 ~ 20,000 rpm) and the resulting highrunning temperature makes cooling performance very important. That is why lightweight aluminum, with its excellent heat transfer rate, is used for motorcycle cylinders. These cylinders made of inherently soft aluminum have a cylindrical cast steel liner inserted along the inner wall of the cylinder to reduce friction resulting from the piston’s movement. Thus they are called “cast steel liner aluminum cylinders.”

This construction, in which a cylindrical steel sleeve is inserted along the inner wall of the cylinder, produces a cylinder which is very reliable from the standpoint of reduced friction and reduced possibility of engine seizure. That is why Yamaha uses this kind of cylinder on approximately 70% of all the motorcycles it manufactures. In the case of models for the markets of Asia and Central and South America, this figure reaches about 90%.
However, there are also problems with the cast steel liner type aluminum cylinder, such as the complexity of the manufacturing process involved in inserting the steel sleeve, the poor recyclability of these cylinders and the limitations in heat transfer rate due to the presence of the cast steel liner (the heat transfer rate of steel is 1/3 that of aluminum). Other problems with cast steel liner type cylinders are environment-friendliness and manufacturing efficiency.

On the other hand, there is an alternative type of cylinder used on high-performance motorcycles that replaces the cast steel liner with a layer of metal plating on the cylinder wall. This kind of “plated cylinder” has superior cooling performance (about 60% better than a cast steel liner type) but also has the problem of higher production cost.

And while the cast steel liner type cylinder and the plated cylinder have been used on different models based on their relative merits, the industry has been seeking next-generation mass-production technologies for cylinders that would stop the rise in production cost and enable the production of cylinders that are both environment-friendly and highly functional.
The Yamaha “DiASil Cylinder” is the product of a new technology that enables the low-cost mass production of an all-aluminum die-cast cylinder with excellent abrasion resistance, high production efficiency, excellent recycling potential and cooling performance equivalent to that of a plated cylinder.