Intake control system for internal combustion engine

Claim 1

In an induction system for an internal combustion engine having a chamber of variable volume in which combustion occurs, main induction passage for delivering a charge to said chamber, an auxiliary induction passage for delivering a charge to said chamber, said auxiliary induction passage having a substantially lesser effective cross-sectional area than said main induction passage so that a given mass flow of charge delivered to said chamber through said auxiliary induction passage will enter said chamber at a significantly greater velocity, valve means for controlling the ratio of communication between said induction passages and said chamber during a given cycle of operation, said valve means being effective to direct substantially all of the idle charge flow to said chamber through said auxiliary induction passage, said valve means comprising at least a butterfly type throttle valve for controlling the flow through said main induction passage, the improvement comprising a relief formed in said butterfly type throttle valve formed at a location spaced above its lower peripheral edge for reducing the velocity of the charge entering said chamber through said auxiliary induction passage when said engine is operating at its idle condition, said relief being oriented so that the charge flowing therethrough when said butterfly type throttle valve is substantially closed will intersect the charge introduced to said chamber through said auxiliary induction passage to increase the turbulence in said chamber.