How does a closed-feed injection carburetor operate?

How does a closed-feed injection carburetor operate?

• A. Fuel is metered by a servo pressure
• B. Fuel is metered through fixed jets according to airflow and discharged under positive pressure
• C. Fuel is metered by variable jets according to RPM
• D. Fuel is not metered and is constant

Answer: (B)

Fuel metering in a closed-feed injection carburetor relies on fixed jets that regulate the amount of fuel based on how much air is flowing. A small pump keeps the fuel under positive pressure so it can be discharged through those jets into the airstream. As air moves through the carburetor, the flow through the venturi creates suction that pulls fuel through the fixed jets and into the intake. Because the jets are fixed, the fuel amount responds to changes in air flow, giving a fuel-to-air ratio that tracks engine demand. This design does not use a servo-driven pressure metering system or variable jets controlled by RPM, and the fuel isn’t kept constant regardless of conditions.

Fuel metering in a closed-feed injection carburetor relies on fixed jets that regulate the amount of fuel based on how much air is flowing. A small pump keeps the fuel under positive pressure so it can be discharged through those jets into the airstream. As air moves through the carburetor, the flow through the venturi creates suction that pulls fuel through the fixed jets and into the intake. Because the jets are fixed, the fuel amount responds to changes in air flow, giving a fuel-to-air ratio that tracks engine demand. This design does not use a servo-driven pressure metering system or variable jets controlled by RPM, and the fuel isn’t kept constant regardless of conditions.