Ford has developed an automatic four-speed transmission system for its Fiesta and Fusion models, which constantly adapts to provide optimum performance for various driving conditions such as towing, climbing or descending hills and heavy acceleration.
The compact Durashift Automatic system, which is intended for the lower end of the Ford range, weighs just 54kg and is claimed to be more fuel efficient than its predecessors. It uses its own dedicated computer control system to allow it to analyse the conditions and adapt accordingly.
The control unit is integrated into the car’s on-board computer system, enabling it to communicate constantly with the engine control module and electronic throttle control, said Glen Goold, manager of B-Car powertrain programmes at Ford.
‘It is all hung together in the management system, which gives us optimum performance. There is a constant analysis of the torque, vehicle speed and engine speed,’ he said.
This analysis allows the transmission control module to determine how the car is being used. ‘So it’s the true brains of the engine. We can optimally calibrate the shift cycles, performance and fuel economy,’ he said.
The electronic throttle control provides a cable-free connection between the accelerator pedal and the powertrain. When the driver depresses the accelerator, a resistor in the pedal communicates electronically with the throttle and engine control units.
‘Historically you have an accelerator pedal with a cable going up to the engine, so you push the pedal first and then the engine says ‘I’m changing gear’, so it was all sequential. Now it is all done instantaneously,’ said Goold.
The transmission is combined with a 1.6-litre, 100hp petrol engine. A twin planetary gearset uses hydraulic clutches to change gear without interrupting power flow, virtually eliminating jolts. If the driver depresses the accelerator hard, the system will downshift to allow quick acceleration. At cruising speed the control unit keeps the engine revving at low speeds to minimise fuel consumption.