The ACD (active center differential) distributes the torque more effectively between the front and rear wheels. In a nutshell, the ACD helps this Evo respond more quickly and effectively to changing traction demands and works to optimize tire adhesion in either tarmac, gravel, or snow modes. The new electronic unit enhances steering response and traction. Electronics govern the cover clamp pressure placed on the center differential clutch pack to match driver input and vehicle condition. Under hard acceleration, the ACD is in a near locked state, transmitting the most torque to the road surface for traction. As the driver makes rapid steering inputs, the center diff operates virtually as an open differential to improve the steering response while retaining the 4WD stability. One of the EVO's coolest features occurs when the parking brake is engaged the ACD will operate as an open diff for quick side brake turns. In addition to the ACD, the EVO still integrates the active yaw control that has proven so successful in previous versions. A computer integrates the functions of the AYC and the ACD so that optimum control and traction are maintained at all times, creating the aura of a car that's almost idiot-proof to drive and as confidence-inspiring as a beer stein full of Jim Beam.