Vehicles having automatic transmissions may be equipped with a torque converter providing a fluid coupling between the powertrain load and the power source. The fluidic coupling is usually such that it allows torque from the power source to be decoupled from wheels at low speeds. While useful to manage differing torques and/or speeds of the power source and load, efficiency losses are incurred related to the differences in speeds.
Hybrid vehicles may employ one or more electric machines having a motor-generator combination in combination with an internal combustion engine. Depending on vehicle operating conditions, an electric machine may selectively alternate between serving as a power source or a load upon the powertrain. The timing of this alternate operation of the electric machine may serve to optimize fuel economy.