Fuel supply metering arrangement

In a carburetor for providing a combustible fuel-air mixture to a conventionally aspirated internal combustion engine having a diaphragm type pressure regulated fuel supply chamber, a fixed size main fuel supply metering orifice and an adjustable idle fuel supply metering orifice with the main fuel supply metering orifice being independent of the idle fuel supply metering orifice and having a check valve in series with the main fuel supply metering orifice for preventing air flow from the main fuel supply metering orifice toward the idle fuel supply metering orifice, an improved temperature compensating fuel supply metering arrangement comprising:

• an idle fuel supply conduit formed in a region of the body of the carburetor extending from the fuel supply chamber to the bore of the carburetor, a mixture control member formed of a material having a temperature expansion coefficient greater than the temperature expansion coefficient of the body of the carburetor, the mixture control member threadingly engaging the carburetor body, and extending into the idle fuel supply conduit, the mixture control member having generally cylindrical means near the end thereof within the fuel supply conduit extending into and closely fitting a generally cylindrical restricted region thereof for controlling fuel flow according to the extent of penetration of the control member into the restricted region, the mixture control generally cylindrical means fitting closely within the restricted cylindrical region and having a generally tapering V-shaped notch extending along one side thereof of varying depth with the depth being greater near the said one end to define an idle fuel supply limiting orifice of generally pie-shaped cross-section between the V-shaped notch and the restricted cylindrical region to define a minimum fuel flow area having a perimeter to area ratio less than about 400 when all measurements are made in inches, carburetor body temperature increase causing an increased penetration of the cylinder means of the mixture control member into the restricted region of the fuel supply conduit and correlative reduction in fuel flow to thereby minimize the adverse effects of ambient temperature changes on carburetor operation.