Air supply control systems for turbocharged internal combustion engines

Abstract

An air supply control system for an internal combustion engine comprises at least first and second turbosupercharger, an exhaust cutoff valve operative selectively to open and close an exhaust passage in which a turbine of the second turbosupercharger is disposed, an intake air cutoff valve operative selectively to open and close an intake passage in which a blower of the second turbosupercharger is disposed, a cutoff valve controller operative to control the exhaust cutoff valve and the intake air cutoff valve so as to cause the first turbosupercharger to work when intake air mass flow fed to the engine is to be relatively small and to cause both of the first and second turbosuperchargers to work when intake air mass flow fed to the engine is to be relatively large, an engine operation detector, and an operation controller operative to vary, in response to an engine operating condition detected by the engine operation detector, a boundary between first and second operating areas provided on an operating characteristic chart of the engine respectively for a first supercharging operation in which the first turbosupercharger works but the second turbosupercharger does not work and a second supercharging operation in which both of the first and second turbosuperchargers work.