Abstract: A secondary controller for controlling the performance of an automobile is described. The secondary controller can be configured to temporarily reprogram one or more vehicle controllers, such as the engine control unit, after the automobile has been powered on. The secondary controller can substitute command sets with different command sets by rewriting the corresponding portion of RAM. The secondary controller can receive vehicle information from the engine control unit to determine the particular type of vehicle to locate the particular command in RAM in order to rewrite the command set. In one embodiment, the secondary controller communicates with the vehicle controller via the vehicle's diagnostic port, such as an OBD-II port. In another embodiment, the secondary controller can be configured to control a variable displacement engine in a vehicle to command the vehicle to operate using all available cylinders.

Abstract: A secondary controller for controlling the performance of a vehicle is described. The secondary controller sends control commands to a vehicle controller while the vehicle is being driven to effect the operation of the vehicle's power train without requiring any modification of the vehicle controller and without falsifying any information sent to the vehicle controller. In some embodiments, the secondary controller communicates with the vehicle controller via the vehicle's diagnostic port, such as an OBD-II port. In one aspect, the secondary controller is used to direct the vehicle controller not to utilize a start/stop feature to automatically turn off the engine in the selected circumstances during normal operation of the vehicle. As such, the control command causes the vehicle controller to operate the vehicle in the selected operating mode in manner dictated by the engine controller.