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The automobile industry presently focuses on improving fuel economy and reducing the weight of vehicles. One part of these efforts is to develop high-performance engines for improved combustion efficiency and lower emissions. Against this background, many high-performance motorcycle engines use forged pistons made of extruded or continuously cast aluminum alloy for high reliability and material properties. The cost of forged pistons is higher than that of gravity die cast pistons. To replace these expensive forged pistons, a low-cost, high-performance piston with increased endurance and thermal resistance has been developed using a newly developed aluminum alloy and a high-quality die casting technology using an oxygen supply system and additional pressure.

An ultrasonic soldering process was developed for manufacture of a compact and lightweight water pump case for sport-utility motorcycles. Most standard water pump cases consist of an aluminum pump case and a steel pipe brazed to a steel flange. Conventional joint method of an aluminum pump case to a steel pipe is by bolting. Our modified ultrasonic soldering succeeded in joining an aluminum pump case and a steel pipe without any flange or bolt. Also by adopting an oval joint shape, the water pump case became more compact and has been produced with elimination of 4 parts. Its weight was lessened by approximately 16% from the previous one. It has been considered difficult to join steel and aluminum because of the formation of fragile intermetallic compounds. We prevented, however, the formation of intermetallic compounds by ultrasonic soldering. We verified that water pump cases joined to a steel pipe by ultrasonic soldering have excellent joint strength and high reliability.

SiC whiskers reinforced aluminum alloy was applied to the piston head of outboard engines. It enables to achieve high performance and high output. In this result, the engine with this piston exhibit the power 12.5% (200Ps → 225Ps) larger than that with un-reinforced piston. Without changing the weight of the piston, and enabled development of a highly durable engine which can withstand severe conditions over a long lifetime. This developed piston was made in a squeeze casting process with SiC whisker preform, into which a molten aluminum alloy were infiltrated under high pressure. This paper explains the preform fabrication method of the SiC whiskers, as well as the composite fabrication methods based on squeeze casting. It also describes the mechanical properties of this composite, such as tensile strength, hardness, coefficient of thermal expansion and density, while comparing it with the aluminum alloy from room temperature to high temperature.