A valve assembly for a compressor of an internal combustion engine, the valve assembly comprising: an evacuator having a motive cone, a discharge cone, and a suction port, wherein a motive outlet end of the motive cone faces a discharge inlet of the discharge cone to define a Venturi gap in fluid communication with the suction port; and a variable relief valve (230, 310) having a plurality of partially open positions and a closed position, the relief valve comprising: a housing defining an inlet and an outlet in selective fluid communication with one another controlled by the movement of a piston (108, 312) enclosed within the housing, wherein the piston (108, 312) and the housing define a pressurized chamber (106, 342) in fluid communication with the suction port of the evacuator and define a second chamber in fluid communication with the inlet and the outlet of the variable relief valve (230, 310); wherein the variable relief valve (230, 310) comprises a valve element connected to one end of the piston (108, 312), wherein the valve element includes a head that selectively blocks fluid from flowing from the inlet to the outlet; wherein the piston (108, 312) translates within the pressurized chamber (106, 342) towards the open position if vacuum is applied to the pressurized chamber (106, 342), said valve assembly being characterized by a vent valve fluidly connected to the pressurized chamber (106, 342), wherein the vent valve varies an amount of vacuum in the pressurized chamber (106, 342) to control a position of the piston (108, 312) within the pressurized chamber (106, 342) to be any one of the plurality of partially open positions even when the evacuator applies vacuum to the pressurized chamber (106, 342). an evacuator having a motive cone, a discharge cone, and a suction port, wherein a motive outlet end of the motive cone faces a discharge inlet of the discharge cone to define a Venturi gap in fluid communication with the suction port; and a variable relief valve (230, 310) having a plurality of partially open positions and a closed position, the relief valve comprising: a housing defining an inlet and an outlet in selective fluid communication with one another controlled by the movement of a piston (108, 312) enclosed within the housing, wherein the piston (108, 312) and the housing define a pressurized chamber (106, 342) in fluid communication with the suction port of the evacuator and define a second chamber in fluid communication with the inlet and the outlet of the variable relief valve (230, 310); wherein the variable relief valve (230, 310) comprises a valve element connected to one end of the piston (108, 312), wherein the valve element includes a head that selectively blocks fluid from flowing from the inlet to the outlet; wherein the piston (108, 312) translates within the pressurized chamber (106, 342) towards the open position if vacuum is applied to the pressurized chamber (106, 342), said valve assembly being characterized by a vent valve fluidly connected to the pressurized chamber (106, 342), wherein the vent valve varies an amount of vacuum in the pressurized chamber (106, 342) to control a position of the piston (108, 312) within the pressurized chamber (106, 342) to be any one of the plurality of partially open positions even when the evacuator applies vacuum to the pressurized chamber (106, 342). a housing defining an inlet and an outlet in selective fluid communication with one another controlled by the movement of a piston (108, 312) enclosed within the housing, wherein the piston (108, 312) and the housing define a pressurized chamber (106, 342) in fluid communication with the suction port of the evacuator and define a second chamber in fluid communication with the inlet and the outlet of the variable relief valve (230, 310); wherein the variable relief valve (230, 310) comprises a valve element connected to one end of the piston (108, 312), wherein the valve element includes a head that selectively blocks fluid from flowing from the inlet to the outlet; wherein the piston (108, 312) translates within the pressurized chamber (106, 342) towards the open position if vacuum is applied to the pressurized chamber (106, 342), said valve assembly being characterized by a vent valve fluidly connected to the pressurized chamber (106, 342), wherein the vent valve varies an amount of vacuum in the pressurized chamber (106, 342) to control a position of the piston (108, 312) within the pressurized chamber (106, 342) to be any one of the plurality of partially open positions even when the evacuator applies vacuum to the pressurized chamber (106, 342).