Development of a New Variable Venturi Carburetor

A new variable venturi carburetor has been developed, in order to achieve high metering accuracy, fuel economy, higher power and good driveability of the vehicle. This carburetor is a down-draft-type, and has better characteristics compared with the fixed venturi carburetor, such as better fuel atomization, lower cycle-to-cycle variation of combustion in lean mixture, faster response, and higher power. For this carburetor, a new type venturi and a new cold enrichment system has been developed. This venturi type has an exponential-profile with a nearly constant increasing rate of venturi opening area to the suction piston stroke. The new cold enrichment system controls the air-fuel ratio in all conditions by changing air bleed quantities using the thermowax. With this system, cold driveability is improved greatly.