In naturally aspirated (non turbo charged) diesel engines such as cars or trucks that can travel through varying terrain and altitudes, a means by which the fuel delivery rate can be altered is an important function of the governor and altitude pressure compensator. Since atmospheric pressure decreases with an increase in altitude, the volumetric efficiency of the engine will be less at higher elevations than it will be at sea level. On turbocharged engines, a boost compensator performs a function similar to that of the altitude compensator on nonturbocharged engines. Bosch refers to the altitude compensator as an ADA mechanism, and it is used in conjunction with either the RQ or RQV mechanical governor models. The ADA is located on the governor cover.