In the probably most frequently used partial load area, in contrast to the later developed regulated catalytic converter cars, a relatively lean mixture used to be set to keep the fuel consumption down.
Through a small tapering in the actual air funnel, a vacuum is created corresponding to the air-flow speed. This vacuum sucks pre-foamed fuel from the center nozzle (air correction nozzle). This nozzle immerses, together with the other two, the idling air- and the idling fuel nozzle, into the fuel in the float chamber. The inflow of the fuel is limited by the main jet which is also laid out as an immersion nozzle. Thereby, it is effectively protected against fouling. The air correction jet has, towards the top, finely calibrated borings, through which the brake air flows in. In the lower part, it is made up of a perforated tube. The brake air streams into the tube and reaches, depending on the air-flow speed, further higher- or lower lying perforations. While immersing, and while flowing through the perforations, fuel is also drawn off. It is sucked in through the auxiliary funnel (auxiliary venturi). The more that is sucked in, the more brake air is found in the fuel flow. The mixing proportion thereby, remains almost constant. 01/11