Abstract
An air-cooled 4 stroke single-cylinder general purpose engine with 438 cm3 of displacement was researched to improve fuel efficiency. As a technique for improving fuel efficiency, 1) Intake valve were narrowed and spark plug was moved closer to the bore center. As a result, the new engine shortened the mass combustion rate by 13%, compared to existing engines, and improved fuel efficiency in the EPA general-purpose mode by 1.1%.2) Taking aim at reducing the piston system friction, piston ring tension was lowered 45% compared to that of existing engines in the same class by using a centrifugal casting sleeve with the air-cooled engine. This has resulted in a 5% reduction in friction mean effective pressure, and improved fuel efficiency in the EPA general-purpose mode by 0.9%. 3) Electronic control technology was used, and ignition timing was decided based on engine speed and throttle opening data. This has improved fuel efficiency in the EPA general-purpose mode by 1.1%, while at the same time piston noise was reduced. Totally fuel efficiency was improved 3.1% by these three technologies. Additionally revising the carburetor setting and auxiliary equipment, the newly developed engine increased fuel efficiency in EPA general-purpose mode by 15% over that of existing engine.
Keywords: General purpose engine, Fuel consumption, Piston noise