Intake device for an internal combustion engine

Abstract

An intake system for an internal combustion engine includes a variable length intake tract having a moveable intake pipe which selectively abuts a fixed intake pipe. During high speed operation, the moveable intake pipe is separated from the fixed intake pipe to provide a relatively short intake pipe length while in low speed operation, the moveable intake pipe abuts the fixed intake pipe so that a longer intake tract is formed. The influence of positive pressure waves on the air/fuel ratio during low speed operation is reduced by air flow resistance control means which increases the resistance of the intake system during low speed operation. This may be accomplished by use of an induction housing having a high speed chamber receiving the outlet of the fixed intake pipe and a low speed chamber receiving the outlet of the intake system when in the low speed intake mode, the low speed chamber having an intake opening having a higher air flow resistance than that of the opening of the high speed chamber. The intake system when used in a multi-cylinder engine may drive the moveable intake pipes of differing cylinders so that the transient shifting of the moveable intake pipe between the low speed mode and the high speed mode occurs at slightly different times for differing cylinders reducing the power droppage at any instant in time for the overall engine.