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Technical Paper

Fuel Injection System of Air-cooled Engines for Small Displacement Motorcycles

With the interest in global environmental issues growing in recent years, the demand for the reduction of exhaust gas emission and improvement in fuel consumption for small motorcycles has increased greatly. Recently, small motorcycles have been marketed equipped with an electronically controlled fuel injection system effective in reducing emissions and enhancing fuel consumption by accurately controlling the air-fuel ratio. The small motorcycles' market comprises mainly ASEAN countries, and the majority of the motorcycles consist of reasonably priced models with air-cooled engines. Fuel injection systems have already been adopted for motorcycles equipped with water-cooled engines in the markets of advanced countries, mostly in EU. Given the above situation, two issues must be addressed to adopt a successful fuel injection system for air-cooled, low-priced small motorcycles.
Technical Paper

Control Device of Electronically Controlled Fuel Injection System of Air-cooled Engines for Small Motorcycles

In conventional electronically controlled fuel injection systems, when the battery is inadequately charged, the small amount of electric power generated from the alternator by the kick starter operation is consumed by all electrical loads including the battery. This causes a voltage drop, hence the fuel injection system does not function due to a power shortage. To eliminate the power shortage, an installed relay circuit opens all electric loads other than the fuel injection system. This allows the fuel injection system to use all the electric power generated by the kick starter operation aided through using an additionally incorporated condenser. This type of electric power control system has been incorporated into the ECU. Thus, the control system has been realized that permits starting of an engine by using the kick-starter even when the battery is completely discharged.
Technical Paper

Research into New Emission Control Techniques for Motorcycles to Achieve the EURO-3 Regulation

This emission reduction technique has been researched on motorcycles equipped with a four-cylinder, liquid-cooled engine of 1100cm3 displacement in order to comply with the EURO-3 emission regulation. The EURO-3 emission regulation will be enforced in Europe beginning in year 2006. Compared to the EURO-2 regulation, reduction of cold-start HC and reduction of NOx from the extra-urban driving cycle are the main issues for EURO-3 compliance. The hydrocarbon reduction during cold-starting was achieved by the method of early catalyst activation using a combination of an Idle Air Control Valve system (IACV), ignition-retard, and atomization of fuel spray. In the extra-urban driving cycle, the fine controlled air-fuel ratio reduced. In addition, optimization of the number of three-way catalyst cells and their capacity also reduced NOx. Moreover, power loss decline caused by increased exhaust resistance due to increasing the catalyst size was avoided by optimizing the catalyst location.