Manifold pressure regulation for pneumatic brake booster in a lean-burn engine

摘要

A lean-burn internal combustion engine capable of stably securing a satisfactory vacuum for a vacuum actuator which uses a vacuum in an intake manifold disposed on the side downstream of an intake air amount control mechanism, while preventing a deterioration of a specific fuel consumption and a drivability of the engine. A filling state of gases in the intake manifold is controlled based on pieces of information in respect of an engine operating state and a reduction in vacuum, whereby a vacuum such as to ensure the operation of the vacuum actuator is secured. A control for inhibiting a lean-burn operation of the engine and for suppressing an EGR amount or inhibiting the EGR is made in accordance with an braking manipulation, the ON/OFF state of a vacuum switch, or an output from a vacuum sensor at the time of lean-burn operation.