Four stroke engine (PDF)

Issue 6, pp 12-14

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Abstract

Up until now, piston and diaphragm-controlled two-stroke engines have been used almost exclusively for handheld engine-powered equipment, since these — when compared with four-stroke engines — have advantages mainly in regard to simple design, low weight, wide usable speed range and high power density. 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 stricter thresholds in Europe and the USA for pollutant emissions with hand-held engine-powered equipments. This is why Dolmar GmbH developed an innovative oil-ingasoline lubricated high-performance four-stroke engine for chainsaws, which combines the advantages of the two-stroke engine with the low emission of the four-stroke principle.