Exhaust system of an internal combustion engine

摘要

An internal combustion engine having a valve overlapping period control device for controlling a valve overlapping period during which both the intake valve and the exhaust valve are open, and an equivalent length adjustment device for controlling an equivalent length of an exhaust passage necessary to cause an exhaust gas pulsation to return to an exhaust port in the form of a vacuum during the valve overlapping period, to thereby reduce the equivalent length as an engine speed increases when the valve overlapping period is longer than a predetermined period, and for stopping a control of the equivalent length when the valve overlapping period is shorter than the predetermined period.