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Recently, it has been expected that titanium alloy valves will be adopted at extremely high rate to motorcycle engines where higher engine performance is required than in automobiles. However, there were difficulties with respect to reliability required for motorcycle engines. The reason for this is that engine valves of motorcycle engines are not only smaller in stem diameter, but also used at a higher maximum engine speed than those of automobile engines. This study is about a development of titanium alloy engine valves that meet reliability requirements in motorcycle engines.

In October 1998, a new mass-produced car with titanium engine-valves was released from TOYOTA Motor Corporation. Both intake and exhaust valves were manufactured via a newly developed cost-effective P/M forging process. Furthermore, the material which was specially designed for the exhaust one is a unique titanium metal matrix composite (MMC). This paper discusses the materials and manufacturing methods used. The tensile, fatigue strength and creep resistance of the MMC are always superior to those for the typical heat-resistant steel of 21-4N. Both valves have achieved sufficient durability and reliability with a manufacturing cost acceptable for mass-produced automobile parts.

In recent years, the adoption of electronically-controlled fuel injection system (commonly called “FI”) of motorcycles is accelerating for the purpose of fuel efficiency improvement to meet tighter emission controls around the world and to protect global environment. The main stream of the motorcycle market is small motorcycles with an engine size of 100cc to 150cc, therefore downsizing and lowering the cost of FI products are being demanded. Pressure regulator (hereafter called P/R) installed in fuel pump module (hereafter called FPM), one of FI products for motorcycles, is being shifted to ball valve type from diaphragm type due to the downsizing demands. However, the ball valve type has problems such as abnormal noise and pressure adjusting defect that are caused by self-excited vibration.

In recent years, more and more small motorcycles, such as scooters, are introducing Fuel Injection System (FI system) worldwide. As motorcycles have limited component spaces, it is not easy to put the fuel supply system products such as Fuel Pump Module (FPM) and Fuel Injector intended for four-wheel vehicles. Therefore, downsizing of these components are being required. In addition, weight reduction is also an important design factor in terms of improvement in fuel efficiency and driving performance. To meet these needs, we focused on motorcycles to optimize the design. We have been standardizing these components and starting mass-production in order since 2002. This paper introduces FPM and Fuel Injector that were newly developed for motorcycles.