Abstract: A variable area venturi carburetor has a wall movable by a servo controlled by venturi-like control vacuum to vary the area and thereby change airflow capacity and fuel flow; a tapered fuel metering rod is attached to the wall and cooperates with a stationary fuel jet; during cold engine operation, a temperature responsive device progressively blocks the flow of the control vacuum as the temperature decreases, to permit higher ported manifold vacuum also acting on the servo to open the venturi wider to change the fuel metering signal while withdrawing the fuel metering rod, to provide a change in richness. Return to normal temperature causes the control vacuum to bleed the ported manifold vacuum to the control vacuum level.

Abstract: A variable area venturi carburetor has the cold engine cranking and running circuits integrated with the venturi valve circuit, to simplify the construction as compared to known carburetors of this type in which the circuits are independent, the integration being provided by an articulated linkage moving the venturi valve in response to engine manifold vacuum changes, the carburetor having an auxiliary air and fuel passage also controlled by manifold vacuum during cold engine operation to provide controlled air and the extra fuel required for cold cranking and running, and shutting down of the extra fuel supply and opening the air supply when the engine reaches the normal operating temperature.