Internal combustion engine intake system having auxiliary passage bypassing main throttle to produce swirl in intake port

Claim 1

In an intake system of an internal combustion engine, having an induction passage, an intake port as an endmost portion of the induction passage adjoining a combustion chamber of the engine, a main throttle valve installed in the induction passage upstream of said intake port, an intake valve for periodically providing communication of the intake port with the combustion chamber according to the engine cycle, and means for introducing fuel into the induction passage through a fuel nozzle opening into the induction passage at a section upstream of the intake port, the improvement comprising an auxiliary induction passage which has a smaller cross-sectional area than said induction passage and is arranged to bypass said main throttle valve and extend to said intake port, an endmost portion of said auxiliary induction passage taking the form of a conduit which extends in said intake port such generally circumferentially of said intake port and has an open end so shaped as to constitute a nozzle opening into said intake port in a direction generally circumferentially of said intake port such that a gas injected from said nozzle makes a swirling flow in said intake port.