Image Number 3 for United States Patent #4150648.
Disclosed is an exhaust gas recirculation engine for high altitude use. The engine comprises an exhaust gas recirculation control valve device communicating an intake manifold with an exhaust manifold for circulating a part of the exhaust gas for reducing harmful NO.sub.x contaminants contained in the exhaust gas, which device is actuated by vacuum supplied from a vacuum port disposed at a position adjacent to a throttle valve of a carburetor, a reservoir tank for storing a vacuum; a control valve device for controlling the delivery of the vacuum from the reservoir tank; and an altitude compensating device for actuating the control valve device in accordance with the altitude.Utilizing the above-described engine, exhaust gas is recirculated for a predetermined interval of time after the throttle valve has been opened at a level which is more than the predetermined level during high altitudes. However, exhaust gas is stopped from being recirculated as soon as the throttle valve is opened to the predetermined level during low altitudes. As a result, the amount of harmful NO.sub.x contaminants contained in the exhaust gas can always be maintained at a low level.