Intake system for internal combustion engine

Claim 1

In an induction system for an internal combustion engine having a plurality of combustion chambers, a series of first intake passages each having a first effective length for serving a respective one of said combustion chambers, a series of second intake passages each having a second effective length serving a respective one of said combustion chambers, said first induction passages communicating at their inlet ends with a first plenum chamber, said second induction passages communicating at their inlet ends with a second plenum chamber, the effective length of said induction passages being the length between the inlet into the respective plenum chamber and said combustion chamber and the effective lengths of said first and said second intake passages being substantially different from each other, said first intake passages being relatively long and tuned for low speed running and said second intake passages being relatively short and tuned for high speed running, a plurality of first throttle valves for controlling the flow through said second intake passages and a plurality of second throttle valves for controlling the flow through both of said intake passages, said second throttle valves being manually operated, an auxiliary induction passage extending from said second plenum chamber to a point downstream of said second throttle valves, third throttle valve means for controlling the flow through said auxiliary induction passages, and means for providing an atmospheric air inlet only to one of said plenum chambers.