Einrichtung an Kraftfahrzeugen zum Schutz gegen Luftverunreinigung

摘要

An air-pollution preventive system for use with an internal combustion engine of motor vehicles, which system is adapted to reduce the concentration of nitrogen oxides in the exhaust gases emitted from the engine during the city-road driving of the motor vehicle, wherein the exhaust gases are recirculated from the exhaust manifold into the intake manifold and cooled therein when, and only when, the vacuum in the intake manifold is lower than a predetermined level and concurrently the engine is driven at a speed within a predetermined range, such predetermined level and range being determined as corresponding to the vehicle speed at which the motor vehicle is accelerated or climbs up a hill as frequently experienced during city-road driving.