Hybrid vehicle with cylinder deactivation

A hybrid powertrain controller for a vehicle with at least one electric motor/generator and an internal combustion engine having a plurality of working chambers, the hybrid powertrain controller comprising:

• an engine control unit arranged to operate the engine in a variable displacement mode in which some, but not all of the working chambers are fired to add torque to a powertrain of the vehicle and wherein unfired working chambers are deactivated during unfired working cycles, the variable displacement mode having a fixed set of operational states and wherein during operation in the variable displacement mode, an air intake throttle of the engine is held at a substantially fixed position even through some variations in a desired torque output;
• and
• a motor/generator control unit arranged to operate the at least one electric motor/generator to add torque to or subtract torque from the powertrain of the vehicle wherein the hybrid powertrain controller is arranged to coordinate operation of the engine and the at least one electric/motor generator to deliver the desired torque.