Supplementing engine control via a diagnostics port

A method of directing the displacement of a vehicle having a variable displacement engine and a factory engine control unit (factory ECU), the method comprising:

• sending a displacement control command from a device coupled to a diagnostic port associated with the variable displacement engine to the factory engine control unit while the vehicle is being driven, wherein the displacement control command directs the factory engine control unit to cause the engine to operate at a designated displacement that is at least sometimes different than a second displacement that the factory ECU would otherwise direct operation of the vehicle in at the time the displacement control command is sent, and wherein no modification of the factory ECU are required to enable the factory ECU to direct operation at the designated displacement, and wherein both the designated displacement and the second displacement are displacements supported by the factory ECU.

A non-transitory computer readable medium suitable for use in conjunction with an automobile having a variable displacement engine and a factory engine control unit (factory ECU), the computer readable medium comprising programmed instructions configured to:

• send a displacement control command from a device coupled to a diagnostic port associated with the variable displacement engine to a factory ECU while the vehicle is being driven, wherein the displacement control command directs the factory ECU to cause the engine to operate at a designated displacement that is at least sometimes different than a second displacement that the factory ECU would otherwise direct operation of the vehicle in at the time the displacement control command is sent, and wherein no modification of the factory ECU are required to enable the factory ECU to direct operation at the designated displacement, and wherein both the designated displacement and the second displacement are displacements supported by the factory ECU.