|Carter W0 Carburetor Idle System|
The idle system in the W0 carburetor differs somewhat from that employed in W1, WA1 and WD0 carburetors. Gasoline is taken from the float bowl without passing through the metering rod jet as in the other types of carburetors.
The system is as follows: Gasoline flows by gravity from the float bowl through a restriction in th eidle well jet into the idle well below the idle orifice tube, or low speed jet tube. From here fuel flows through this idle tube and from that point on, the system is identical in operation to W1, WA1 and WD0 units. The illustration shows the by pass economizer, bleed and idle port.
In the W1, WA1 and WD0 carburetors, the idle tube takes its fuel supply from between the metering rod jet and the nozzle. On dead idle, the suction on the idle system is much greater than on the nozzle so that all the fuel flows through the idle system. As the throttle is opened, the suction becomes less on the idle port and increases at the nozzle until a point is reached where the nozzle suction is greaer than on the idle system and the later becomes inoperative.
In the W0 independent idle system as the nozzle suction has no tendency to overcome the flow of gasoline through the idle system, a means of decreasing the flow through the idle system was devised. In the top of the idle well is a passage (shown by small x in the illustration) leading to the inside of the bowl.
By venting this well to atmospheric pressure, there is very little suction here due to the suction on the idle system. Hence, the flow of gasoline to the system is controlled by the volume of fuel that will flow through idle well jet due to a gravity head varying from zero to the difference in height between the gas level in the bowl and the bottom of the idle tube.
Another advantage to the vent indicated by "x" is that it will pevent most of the percolation through the idle system.