Automatic Altitude Compensating Device
Governor is equipped with an altitude compensating device to control emissions at various altitudes. On turbo models, this is connected to the intake manifold to also sense boost pressure variations.
As altitude increases, air pressure decreases. The push rod in the compensator moves downward and pushes the main rack, slightly decreasing amount of fuel injected (lean mixture).
When turbo is operating under boost, rack is pushed in other direction and more fuel is injected. Injection pump and governor operation are affected by the compensator when vehicle is operating near sea level or idle RPM.