Research on the New Control Method using Crankshaft Rotational Changes for Electronically Controlled FI System of Small Motorcycle Single Cylinder Engine

In an attempt for further improvement of exhaust gas purification and fuel economy, an electronically controlled fuel injection (FI) system has been applied to small size motorcycles.

As compared to a similar system for cars, FI systems for small two wheeled vehicles are required to be small, lightweight and low cost. In order to meet these requirements, authors developed a new control method of determining the required quantity of fuel. This system removes the intake pressure sensor of the intake pipe that exists in the conventional FI system. From correlating the peak intake pressure in the intake pipe with the quantity of intake air closely, the peak intake pressure is estimated by using rotation change of the crankshaft. The required quantity of fuel is injected into the engine intake pipe determined by the map set up in the peak intake pressure and the fuel injection period.

Thus, it has been confirmed through actual vehicle tests, that this newly developed simulation system is accurate enough to apply to the FI system in an actual vehicle having conventional parts, dimensions, tolerances, and using the combustion area of “air-to-fuel ratio less or equal to 15.” The elimination of the intake pressure sensor contributes to reducing the cost of the FI system.