Air intake system for multi-cylinder engine

A air intake system for multi-cylinder engine comprising,

• a common intake passage for supplying intake air to a combustion chamber of each cylinder,
• a plurality of individual intake passages branching off from said common intake passage so as to supply the intake air to the combustion chamber of each cylinder,
• a rotary-type throttle valve provided for each of the individual intake passages, including a valve body in a circular shape when viewed along its rotational axis which defines a space as a part of an intake passage, and being capable of linearly controlling the amount of intake air supplied into the combustion chambers, wherein, said individual intake passage comprises a low-speed branched intake passage and a high-speed branched intake passage which supply the intake air to said throttle valve, the inside of said valve body of the throttle valve is formed with an in-valve low-speed passage which is adapted to communicate said low-speed branched intake passage with the combustion chamber, and an in-valve high-speed passage which is adapted to communicate said high-speed branch intake passage with the combustion chamber;
• and
• a control means for controlling the opening of the throttle valve in accordance with the engine operational condition so that said low-speed branch passage and said in-valve low-speed passage are in communication with each other when the engine rotational speed is low, and the high-speed branch passage and the in-valve high-speed passage are in communication with each other when the engine rotational speed is high, and said in-valve low-speed passage is designed so as to be in full communication with said low-speed branch passage during the high speed operation.