Abstract: The pedal effort required to change the setting of a governor (13) of an engine increases sharply with increased engine speed. Booster controls have been provided in the art for applying a boost force (F.sub.B), additive to an operator input force (F.sub.L), for opposing the force (F.sub.S) of a governor spring (42) to thus reduce pedal effort at high engine speeds. The improved booster control (15,15a) herein includes an actuating chamber (53,53a) and a control arrangement (51,51a) for controlling fluid pressure in the chamber (53,53a) when the setting of the governor (13) is changed by the operator and in a predetermined ratio to the operator's input force. The booster control (15,15a) has wider application wherein a boosting force (F.sub.B) is desired to supplement an input force (F.sub.L) for controlling movement of a member (23) having an opposing force (F.sub.S) applied thereto.

Abstract: A bolt-on exhaust brake for an internal combustion engine includes a damper movable to open and closed positions, and an air cylinder actuatable to move the damper to its closed position. The damper is openable upon back-pressure reaching 30 psi, so as to avoid damage to the engine.