Closed loop mixture control system using a two-barrel carburetor

Claim 1

A closed loop mixture control system for an internal combustion engine of a roadway vehicle, comprising: a two-barrel carburetor having a primary barrel having a venturi and throttle and a secondary barrel in said carburetor for both receiving fuel and air when depression at the venturi of said primary barrel falls below a predetermined value, the cross-sectional dimension of the primary barrel being smaller than that of the secondary barrel so that evaporation of fuel inducted to the primary barrel is promoted as compared to the evaporation of fuel inducted to the secondary barrel; means for producing a control signal corresponding to the difference between an air-fuel ratio of the mixture combusted in the engine and a stoichiometric air-fuel ratio of the mixture; primary and secondary metering systems associated with the primary and secondary barrels, respectively, for proportioning air and fuel supplied to said engine, said primary metering system comprising a main mixture supply nozzle disposed in the venturi of the primary barrel, means defining an auxiliary mixture supply port disposed in the closed position of the throttle of the primary barrel, a first mixture control valve associated with said main mixture supply nozzle, a second mixture control valve associated with said auxiliary mixture supply port, a throttle position detector operatively connected to the throttle of the primary barrel, and means for selectively coupling said control signal to said first and second control valves in response to a predetermined throttle position of the primary barrel and effective so that said control signal is applied to the second control valve for part throttle operation and to the first control valve for full throttle operation; and means for controlling said primary metering system in accordance with said control signal.