Modifications on the Intake Ports with the Aim to Reduce the Noise of a Two-Stroke-Crankcase-Scavenged Engine

One of the dominant noise sources of small two-stroke-cycle and crankcase-scavenged engines (port covered and uncovered by the working piston) represents the intake noise. The opening and closing of the port of these engines which are used to drive chain saws causes intake oscillations of big amplitudes. These are an important part of the total noise with regard to the point of measurement at the ear of the saw operator.

By using a special intake port shape and the advancing of the port opening the gradient of the cross section course is reduced. The reduction of the total noise level is about 2–4 dB (A) as a function of the speed at full load while the delivery rate and the output remain constant.