Engine intake system

摘要

This invention relates to an internal combustion engine including a plurality of groups of combustion chambers and at least a first expansion chamber and a second expansion chamber. The first and second expansion chambers extend in a lengthwise direction and are separated from each other by a partition wall. The first expansion chamber is connected with one group of combustion chambers through separate branch passages. The second expansion chamber is also connected with another group of combustion chambers respectively through separate branch passages. First and second intake passages are connected at downstream ends with the first expansion chamber and the second expansion chamber, respectively. An auxiliary communicating passage is provided along the partition wall independent from said first and second intake passages and connects the first and second expansion chambers with each other. A length changing device for alternately communicating the first and second expansion chambers with each other by an auxiliary communicating passage of a minimum length and by an auxiliary communicating passage of a maximum length in accordance with engine operating condition is provided. The first and second intake passages have lengths a sum of which is greater than the maximum length of the auxiliary communicating passage.