The new dual dry-clutch Ford PowerShift six-speed automatic available in the Focus and Fiesta enables a 10% fuel economy gain compared to a four-speed automatic transmission, contributing to both cars delivering as much as 40 mpg on the highway. The PowerShift automatic consists of two manual transmissions (in the same case) working in parallel. Each has its own independent clutch unit controlled by computers and fast-acting electromechanical actuators that shift the gears.
One clutch carries the odd gears, 1, 3 and 5, while the other carries the even gears, 2, 4 and 6, and reverse. PowerShift is an automatic because the gear changes are coordinated by a computer that directs the clutches to engage and disengage in a way that provides seamless delivery of torque to the wheels, even during gear changes. Ford PowerShift’s features include:
Torque Hole Fill: A Ford-developed and patented innovation that eliminates the slight hesitation drivers feel during acceleration when the transmission upshifts into a higher gear.
Hill Start Assist: If sensors detect the Fiesta or Focus on a slope of 5 degrees or more, Hill Start Assist automatically prevents the car from rolling backward in the instant when the driver moves his or her foot from the brake to the accelerator. PowerShift’s computer controls the brake pressure and engine to hold the car in place.
Neutral idle: This feature helps improve fuel economy by eliminating the drag a traditional hydraulic transmission puts on the engine when a vehicle is idling.
Reduced weight: PowerShift weighs nearly 30 pounds less than the four-speed automatic transmission in the 2011 Focus. Less weight helps improve fuel economy.
Ford engineers began developing the dual-clutch technology when advances in the speed of processors, memory and the mechanical actuators that shift the gears progressed to the point that a manual transmission could be made to perform as smoothly as an automatic.
The kind of computing power needed in terms of speed and amount of memory advanced to the point where it is now possible to offer the driver fast, crisp and seamless shifts from this advanced transmission at an affordable price.—George Herr, PowerShift calibration supervisor
Since its launch in Fiesta in 2010, Ford engineers have continued to develop and refine PowerShift’s performance and efficiency. The PowerShift for the all-new Focus, for example, offers several new features including a more compliant clutch damper spring design to reduce noise levels. Piero Aversa, PowerShift engineering manager, said the Focus shift schedule has been optimized for the wider torque band provided by the car’s 160-horsepower, direct-injected 2.0-liter engine.
Also new for Focus is the SelectShift Automatic feature. SelectShift allows a driver to change gears—up or down—by pressing a button on the shift handle. By pushing the plus sign button, the transmission upshifts. Push the minus sign button and the car downshifts. The PowerShift computer prevents a driver from downshifting too fast and causing damage from over-revving. In the Focus, drivers also can choose Sport Mode, which changes the timing of the shifts for quicker acceleration.
Ford engineers also worked to improve low-speed responsiveness and smoothness in response to customer feedback.