Yamaha DiASiL Cylinder

"DiASil": A name created as an abbreviation of Die-casting Aluminum-Silicon
Yamaha Motor Co., Ltd. (YMC) has succeeded in the development of an all-aluminum die-cast cylinder with 60% better cooling performance and 30% cheaper production cost than a conventional cylinder (*1). Called the Yamaha "DiASil Cylinder" (*2), this is the world's first all-aluminum die-cast cylinder and it achieves cooling performance equivalent to that of a nickel-plated cylinder, which is currently recognized as the best in the industry, but at a significantly lower production cost than a nickel-plated cylinder.

The material used is a 20% silicon content aluminum alloy, the manufacturing technology is the recently developed Yamaha CF Aluminum Die-cast Technology (*4), which enables the production of an all-aluminum die-cast cylinder. It is Yamaha's exclusive CF Aluminum Die-cast Technology that enables the mass production of a die-cast cylinder made completely of 20% silicon content aluminum alloy, something that could not be done with conventional die casting methods.

Merits of the Yamaha "DiASil Cylinder"
(in comparison to cast steel liner type aluminum cylinders)
(1) 60% better cooling performance is possible
(2) 30% lower manufacturing cost is possible
(3) Excellent recyclability
(4) Enables 30% lighter design
(5) Easily transferred to overseas manufacturing bases

Yamaha CF Aluminum Die-cast Technology = Yamaha Controlled Filling Die Casting. This is a die-casting technology that utilizes precise control of the casting conditions (degree of vacuum in the die, die temperature, injection speed of the molten aluminum) to reduce the amount of gas bubbles in the finished cast piece to just 20% of conventional methods in order to produce higher quality cast parts. Introduced in Feb. 2002.

In general, motorcycle engines run at high rpm (10,000 ~ 20,000 rpm) and the resulting high running 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.

In specific terms, (1) the degree of vacuum in the die, (2) the temperature of the die and (3) the speed with which the molten aluminum is injected into the die are all precisely controlled in order to produce cast metal that has a highly abrasion resistant crystallization character with an even distribution of hard silicon particles. This makes it possible to mass-produce high quality all-aluminum die-cast cylinders without cast cavities.

- Comparison with Conventional Casting Method -

Basic structure for conventional die casting:
Due to conditions under which conventional die-casting occurs, including the degree of the vacuum in the die, the temperature of the die and the speed with which the molten alloy is injected into the die, there is a tendency for gas bubbles to form that limit the ability to cast parts with a good contact surface.

Structure for CF Die-cast Technology used for the Yamaha "DiASil Cylinder:
Due to the facts that (1) the die is enclosed in a box that enables a high degree of vacuum in even complex die shapes with many slides (six time greater vacuum than conventional die casting), (2) more stable molten aluminum temperature because the temperature of the die is controlled and (3) improved injection speed for the molten aluminum (five times faster than conventional die casting), it is possible to mass-produce aluminum cylinders with more complex shapes and good contact-surface quality.