A second light load advance system, shown in Figure 4-61, is available for automotive applications that use min-max governing. In addition to the normal speed advance, light load advance is furnished as a function of throttle angle.
The mechanical light load advance system is used on automotive pumps. It relies on two systems to provide advance. The first system is a servo advance mechanism that is operated by transfer pump pressure and which positions the cam ring in response to throttle setting and engine load.
The second system is composed of a mechanical link between the throttle shaft and the servo plunger. This link is composed of a face cam connected to the end of the throttle shaft and a rocker lever assembly connected to the side of the pump housing by a pivot pin. A roller is attached to the upper end of the lever and rides on the surface of the face cam. The lower end of the lever contacts the protruding end of the servo advance plunger.