Helically-shaped intake port of an internal-combustion engine

摘要

An engine comprising an intake port which has a separating wall projecting downwardly from the upper wall of the intake port. The separating wall defines a helical portion, an inlet passage portion tangentially connected to the helical portion, and a bypass passage interconnecting the inlet passage portion and the helical portion. The side wall of the helical portion has a slightly inclined portion located near the outlet portion of the bypass passage and expanding towards the separating wall so as to define a narrow passage portion between the inclined portion and the separating wall. A rotary valve is arranged in the bypass passage and is actuated by a vacuum-operated diaphragm apparatus. The rotary valve is opened when the amount of air fed into the cylinder of the engine is increased beyond a predetermined value.