Development of a Valve Controlled Four-stroke Chainsaw to Meet Future Emission Regulations

Up to now, piston or diaphragm-controlled two-stroke engines have been used almost exclusively in hand-held engine-powered equipment. Compared to four-stroke engines, they offer advantages with regard to their simple design, low weight, a wide useful speed range, and high power density. However, a disadvantage is the high hydrocarbon emissions which, due to the principle design are caused by the significant gas-exchange losses. In the future, the simple two-stroke engine will no longer be able to meet the increasingly strict pollutant emission thresholds applicable to hand-held engine-powered equipment in Europe and the USA. For this reason, an innovative mixture-lubricated high-performance four-stroke engine for chainsaws was developed. It combines the advantages of the two-stroke engine with the low emissions of the four-stroke principle.