Methodology of Minimum Energy Starting for SI Engine

In general-purpose small SI engines, it is necessary to reduce fuel consumption under operating conditions involving repeated starts and stops. In other words, the energy distribution during the transition from 0 rpm to idling speed is a crucial factor. At startup, the SI engine must be driven by a motor, and the electrical energy required should be minimized. However, the engine must accelerate during this process, and the required electrical energy is influenced by factors such as compression, friction, and moments of inertia. The purpose of this research is to experimentally clarify the conditions for minimum energy starting in SI engines. Specifically, the effect of the moment of inertia was eliminated by using a motor to maintain a constant engine speed, thereby enabling the isolation and measurement of electrical energy consumed by friction. The electrical energy required to overcome the moment of inertia can be determined by comparing it with the energy consumed when accelerating the engine from 0 rpm. Furthermore, the effect of compression can be evaluated by considering the moment of inertia and friction of individual engine components. This study proposes a method for achieving minimum-energy starting in small engines. Two key conditions for minimizing energy use during startup are the acceleration time to reach idling speed and the crank position at the moment of engine ignition.