A driving force control system for a vehicle having a mechanism for changing an engine speed continuously. The driving force control system basically controls said mechanism in a manner such that the engine speed is adjusted to optimize fuel economy. The driving force control system is configured to determine an index representing a demand to enhance agility of behavior of the vehicle based on an actual behavior of the vehicle or an amount of operation carried out by a driver to cause said behavior. An upper limit value of the engine speed of the case in which a drive demand is increased is determined on the basis of the index, and the upper limit value is set to the higher value with an increase in the index representing the demand to enhance agility of behavior of the vehicle.

A control device that controls a vehicle drive device in which a first engagement device, a rotary electric machine, and a second engagement device are arranged in this order from an internal combustion engine on a power transmission path that connects the internal combustion engine to wheels. The control device is configured to determine an operation stop of the internal combustion engine in a state in which torque is transmitted from the internal combustion engine to the wheels, the control device executes rotational speed control that controls output torque of the rotary electric machine such that a rotational speed of the rotary electric machine approaches a target rotational speed and executes torque-down control that causes output torque of the internal combustion engine to decrease.

Methods for controlling vacuum within a brake booster by modifying powertrain operation include determining an intake manifold vacuum in response to actuation of a brake pedal. Increasing the intake manifold vacuum if the brake booster vacuum is less than a desired brake booster vacuum. In some embodiments, the transmission is downshifted to increase engine speed and intake manifold vacuum. In other embodiments, engine torque is reduced to increase intake manifold vacuum and the torque of the electric machine is increased to maintain a constant output torque.