Improving Flow Tolerances of Mass Produced Carburetors through Pilot System Design

Carburetors are widely used for two wheeler applications in India as well as countries like Taiwan, Indonesia and China. These carburetors are characterized by simple design and low cost. As the emission norms are becoming more and more stringent, matching the carburetors for vehicle application becomes very challenging. Earlier it was widely believed that, for meeting the Euro-3 regulations, even two wheelers with small engine capacity had to employ electronic fuel injection. However, many vehicle manufacturers have successfully developed carburetors for meeting Euro-3 norms by employing catalytic converters without any electronic control. This development has been essentially motivated by the need for low cost.

Flow variation is inherent in mass produced carburetors because there are many parts, which contribute to the air-fuel ratio delivered by the carburetor. Carburetors with the mixture control pilot systems were mass-produced and compared for results with air control system. Results indicate that mixture control system for pilot circuit gives consistently good performance resulting in reduced rejection at manufacturing stage and consistent performance in the vehicle.