PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
c. High-Speed and High-Speed Enrichment Circuits.
(1) Purpose. The high-speed circuit supplies the fuel-air mixture to
the engine during medium to full throttle valve opening.
circuit gradually will take over from the low-speed circuit as the throttle
is depressed. The carburetor is designed to provide approximately a 16:1 to
17:1 air-fuel ratio under normal, steady speed conditions. The high-speed
enrichment circuit will enrich the mixture to approximately 11:1 to 12:1 if
a heavy demand is placed on the engine.
(2) Operation (figure 16). The high-speed circuit takes its gasoline
from the float bowl through the main jet.
The gasoline is fed through a
passageway to the discharge nozzle, where it sixes with the air in the
Opening the throttle valve and accelerating the engine speed
increases the airflow in the venturi, which causes a proportional increase
in the amount of gasoline from the discharge nozzle.
enrichment system increases the fuel flow to the discharge nozzle by either
increasing the main jet