Secondary Main System:
The Secondary Main System (Figure 5) delivers fuel only when thesecondary throttle blades and air valve are open. It ensures that fuel delivery varies with air flow.The Secondary Throttles (1) begin to open when the Primaries are about 65% open. The Primary andSecondary Throttles arrive at the WOT stop at the same time.Air flow through the Secondary side is controlled by Air Valves (2). These valves are located in thesecondary bores above the throttle blades. They are balanced against a counter weight and open toadmit additional air flow only if there is enough air velocity to allow the proper operation of the
Secondary Auxiliary System
During the initial stages of Secondary Operation, the air flow rate through the secondaries is very low.Accordingly, there is not enough pressure drop (suction) at the Secondary Nozzle to induce fuel flow.In order to prevent a lean A/F condition that would be experienced by the driver as a
“bog” or “flat spot” on secondary opening, it is necessary to add fuel by an auxiliary means during thetime the secondary is in the transient phase.