Abstract: A variable intake manifold characterized by a variable cross-section bladder disposed within the engine's intake manifold. The degree of inflation of the bladder, and consequently the degree of occlusion of the cross-sectional flow path available for the fuel/air mixture within the manifold, is controlled by a pressure or vacuum device connected to a control unit. The control unit is adapted to receive status signals relating to the engine temperature, the throttle conditions, the engine speed in revolutions per minute (RPM) and manifold vacuum. These signals are processed by the control unit and result in various signals being delivered to the pressure-vacuum providing mechanisms which modify the degree of inflation of the bladder in accordance with the parameter status conditions.