OPERATION - Engine Brake Valve (Ds range)

In "Ds" position, the plunger allows the circuit to drain, the engine brake valve spool is overcome by spring pressure and moves to the left. The engine brake valve arm, therefore, moves the shift control valve to the left, regardless of the position of the shift cam. This situation maintains pressure at the primary pulley, ie does not allow the shift cam to control pulley ratio variation, and so, as the vehicle speed decreases, it "pulls down" the engine speed with it, giving an engine braking effort.