Fuel Injection System for Smaller Motorcycles Tomoji Nakamura Takahiko Hasegawa Masashi Suzuki Michihisa Nakamura Yuuichirou Sawada ? Engine Development Div …

OUTLINE OF THE FI SYSTEM The FI system which is intended for highly precise control of the air?fuel mixture ratio is an electronically controlled system consisting of a variety of sensors actuators and an ECU (Engine Control Unit shown in Fig.1 . This system has a long history of nearly 30 years of use in automobiles. It works to calculate the optimum fuel injection amount based on information about the air volume engine conditions environmental factors and the rider’s actions detected by various sensors and then feed a highly precise amount of fuel coming in a pressurized state from the fuel pump through the injector and into the engine. AIM OF THE DEVELOPMENT We took up the following four development issues for an FI system for smaller motorcycles. (1 Low cost (2 Small and compact (3 Low electric power consumption (4 Improved engine performance In the following we report on our approaches to the individual issues. Low electric power consumption Electric power generation loss cannot be ignored in smaller motorcycles because their engines do not produce much power output. It is also dif?cult to use a generator (alternator with a large diameter. It is therefore necessary to reduce the amount of electricity the (FI system consumes. The system used in a larger?displacement motorcycle consumed a little over 5A but reviewing the fuel ?ow and improving ef?ciency in collaboration with AISAN INDUSTRY CO. LTD. made it possible to reduce the consumption to 1.7A about a third of 5A. Performance In addition to the environmental contribution we also gave consideration to boosting engine performance with this FI system. Namely we employed a suction piston and wax type fast idle mechanism that have performed so well on larger?displacement motorcycles. In combination with the FI system with its ability to provide optimum control in the different running conditions the former produced a great improvement in drivability in transient conditions and the latter made a contribution to improved starting ability in different environmental conditions.

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