A method, comprising: operating an engine having an engine intake manifold coupled to a pump output of a pump, wherein a continuous variable transmission is coupled to the engine and to the pump; and operating the continuous variable transmission by changing a control ratio operated by a servo motor in response to a control signal sent from a controller of the engine to control the pump speed such that pressure output of the pump is in a range from a vacuum pressure to another pressure higher than atmospheric pressure; operating a valve arranged between a pump input of the pump and the engine intake manifold or within a line bypassing the pump such that the valve is open before and during a ratio change of the continuous variable transmission, wherein changing the control ratio of the continuous variable transmission causes the pump to increase pressure at a point along a flow path between the pump output and the engine intake manifold, and wherein operating the valve comprises: opening the valve to decrease the pressure caused by the pump at the point along the flow path between the pump output and the engine intake manifold to change a shift torque exerted on the continuous variable transmission during the ratio change, wherein said opening the valve is in response to the control signal sent from the controller of the engine to control position of the valve, and wherein opening the valve comprises pulsing an actuator of the valve to allow pressure to be released therethrough in a controlled method without releasing all the pressure at the point along the flow path between the pump output and the engine intake; and closing the valve after the ratio change. operating an engine having an engine intake manifold coupled to a pump output of a pump, wherein a continuous variable transmission is coupled to the engine and to the pump; and operating the continuous variable transmission by changing a control ratio operated by a servo motor in response to a control signal sent from a controller of the engine to control the pump speed such that pressure output of the pump is in a range from a vacuum pressure to another pressure higher than atmospheric pressure; operating a valve arranged between a pump input of the pump and the engine intake manifold or within a line bypassing the pump such that the valve is open before and during a ratio change of the continuous variable transmission, wherein changing the control ratio of the continuous variable transmission causes the pump to increase pressure at a point along a flow path between the pump output and the engine intake manifold, and wherein operating the valve comprises: opening the valve to decrease the pressure caused by the pump at the point along the flow path between the pump output and the engine intake manifold to change a shift torque exerted on the continuous variable transmission during the ratio change, wherein said opening the valve is in response to the control signal sent from the controller of the engine to control position of the valve, and wherein opening the valve comprises pulsing an actuator of the valve to allow pressure to be released therethrough in a controlled method without releasing all the pressure at the point along the flow path between the pump output and the engine intake; and closing the valve after the ratio change. opening the valve to decrease the pressure caused by the pump at the point along the flow path between the pump output and the engine intake manifold to change a shift torque exerted on the continuous variable transmission during the ratio change, wherein said opening the valve is in response to the control signal sent from the controller of the engine to control position of the valve, and wherein opening the valve comprises pulsing an actuator of the valve to allow pressure to be released therethrough in a controlled method without releasing all the pressure at the point along the flow path between the pump output and the engine intake; and closing the valve after the ratio change.