Fiesta 3-door Model Showcases The New Durashift Est Transmission
The new Fiesta three-door debuts Ford's Durashift EST (Electronic Shift Technology) system, a new automatic shift manual transmission that gives drivers the benefits of an automatic transmission without the typical drawbacks of small-car automatics.
Durashift EST will be available as an option on new Fiesta 3-door models equipped with either the Duratec 16V 1.4-litre petrol engine or, more unusually for this segment, with the 1.4-litre Duratorq TDCi common rail diesel engine. The new five-speed automatic/manual select transmission further enhances the refinement and driving quality of Ford’s small-car, and will be available across the Fiesta range.
“This new technology is essentially an intelligent manual with an automatic mode,” said Glen Goold, chief programme engineer. “Durashift EST adapts to changing driving conditions, like hills and curves, making it ideal for drivers who would prefer an automatic but don’t want to pay a penalty in terms of performance feel or fuel economy.”
Durashift EST is an electro-mechanical adaptation of the Ford iB5 manual transmission that offers considerable benefits over traditional automatic transmissions currently on the market.
Three small electric motors take the place of the clutch pedal and the cables normally required by the clutch and shifting mechanism. Two of these motors do the shifting work for the driver, and the third motor, supported by a strong spring, actuates the clutch. This arrangement simplifies the driver’s tasks and contributes to more economical vehicle operation.
This new technology allows the vehicle to perform economically in the highest gear possible for the driving circumstances, such as in commuting traffic, while having the flexibility to downshift one or more gears instantaneously when the driver opens the throttle slightly. This makes overtaking easy without the driver having to worry about shifting gears. The result is a pleasant combination of maximum ease-of-use and low fuel consumption.
Durashift EST is designed to be extremely robust and has been targeted to be maintenance-free for up to 240,000 kilometres. Its smooth electronic shift actuation helps to reduce wear on the clutch and gears.
Consisting of two modes – "Auto Shift Mode" (ASM) and “Select Shift Mode” (SSM) – Durashift EST offers Fiesta drivers the respective benefits of both automatic and manual drive in one system.
The Durashift EST has been designed to give Fiesta drivers an intuitive interface with the transmission system, offering the choice of shifting manually in SSM mode or choosing the ASM automatic shifting option.
A new-style gear lever controls the system, and there is no need for a clutch pedal.
In ASM mode, the driver engages D (drive) from the N (neutral) position to place the vehicle in automatic mode.
To engage SSM mode, the lever is toggled leftward from the D position and then upshifts are actuated by flicking the gear lever rearward (Tip +). Downshifts are actuated by flicking the gear lever forward (Tip -).
The driver can change between ASM and SSM at any time. The last gear remains engaged until a Tip+ or Tip- signal occurs, except to initiate a downshift when the vehicle speed becomes too low for the demanded gear, to prevent stalling.
In driver-actuated SSM mode, Durashift EST does the traditional job of the manual-transmission driver – reducing engine speed, actuating the clutch, selecting a new gear, releasing the clutch and resuming engine speed – smoothly, quickly and efficiently.
In ASM mode, Durashift EST automatically makes the shift decisions, allowing the driver to concentrate on other aspects of driving.
“Tremendous attention to detail has gone into this technology to complement Fiesta’s driving quality,” said David Myers, Fiesta Powertrain Manager. “This transmission shifts seamlessly and in SSM mode, it even performs a little blip of the throttle, just like a skilled manual driver does, when downshifting. And it has the ability to adapt to your driving style of the moment, which means Durashift EST-equipped Fiestas adapt to the driver rather than the driver having to adapt to the car.”
The Durashift EST shifter includes an electronic position detection system – to avoid unintentional shifts by the driver – comprising contactless Hall-effect sensors. These are placed within the base of the shifter housing to ensure durability and resistance to wear over the life of the transmission.
Ford’s Durashift EST is part of an overall integrated powertrain system that includes the engine, transmission and braking systems (ABS, ESP) and is comparable to systems of many luxury cars currently on the market. The system includes input from the transmission via the Control Area Network (CAN bus), which can demand changes in torque in certain shift situations, causing the engine to respond via the engine control unit.
A Transmission Control Unit (TCU) is integrated into the clutch actuator. The TCU gives commands to electric motors that control the shift and select mechanisms in the gearbox and the electric motor in the clutch actuator itself, which operates the hydraulic line for the clutch release system.
The TCU is the Durashift EST’s highly sophisticated microprocessor brain. It reads data from the sensors – including a travel sensor in the clutch, incremental sensors in the electric motors and sensors at the shifter – and communicates via the CAN bus. This allows it to analyse driver input and communicate with the engine control unit.
In the new Fiesta, Ford’s Durashift EST system has a distinctive shift map that prevents sudden gear changes and “hunting” that can occur in automatic transmissions. By selecting the proper shift strategy for each situation, Ford Durashift EST changes gears smoothly with little interruption of power.
In total, the system has three electric motors: one is integrated in the clutch actuator and operates, via a mechanical cylinder, the hydraulic line for the clutch release system. The second electric motor selects the gear and the third initiates gearshift.
In the automatic mode, Durashift EST uses state-of-the-art software in the TCU to evaluate instantaneously input from the various sensors in the system – the angle of the throttle pedal related to torque output, wheel speed and various other parameters – to initiate exactly the right gear and power output for the driving situation.
Ford’s Durashift EST is equipped with various safety features to make driving more worry free and to extend the Fiesta’s reputation for dependability.
Clutch Overheat Protection – Durashift EST has built-in clutch overheat protection in case of excessive operating temperatures, which can be caused by, for example, abusive driving. This feature helps to extend the life of the clutch. Based on the characteristic thermal capacity of the clutch plate, the system constantly monitors heat input by calculating it from slip and torque. The model is initialised using the last clutch-temperature and the current engine temperature. If the system detects too much clutch heat, and the driver does not let up on the accelerator, such as in a slow-start uphill situation, the system produces an intentional jolt to signal the driver. If the driver continues to accelerate even after jolting, the clutch is engaged in order to reduce engine speed, allowing smoother start up and drive.
Creep – Durashift EST is similar to traditional automatic transmissions in that when the Fiesta is in the drive or reverse positions, with the foot brake released and the accelerator pedal in the idle position, the clutch is engaged slowly for a smooth build up of so-called ‘creep torque.’ This avoids sudden jerks of the car in stop-and-go traffic and extends the life of the clutch.
Unique Operational Modes
Downhill Detection – Downhill driving is detected by a comparison of vehicle acceleration and driving torque data. When the downhill mode is activated, the system reacts with an up-shift prohibition below a certain engine speed. When the brake is activated, the system requests a downshift.
Driving Resistance/Uphill Detection – The Durashift EST system detects when Fiesta is moving uphill or pulling a trailer by comparing vehicle acceleration and driving torque, and it can adopt different shifting strategies accordingly. Three gradient shift patterns are available to the system, selected automatically as a function of the driving resistance detected, and are pre-programmed to prevent excessive shift frequency. This tailored approach to driving on gradients enhances driving quality, helps to reduce wear on the system and improves fuel economy.
Fast-off Detection – If the driver suddenly removes foot pressure from the accelerator pedal, the fast-off mode is activated and upshifting is inhibited until the accelerator pedal is activated again. This provides Fiesta drivers with smooth acceleration in uncertain situations.
Curve Detection – Enhancing Fiesta’s class-leading driving dynamics, Durashift EST’s curve detection mode detects when the car is in a curve by comparing the speed of the drive and non-drive wheels. Depending on circumstances, the system can inhibit upshifting during the manoeuvre to follow as closely as possible the driver’s intentions. It can also inhibit downshifting to similarly prevent gearshifts the driver would not normally initiate.
Clutch Torque Follow Up Strategy – Durashift EST clutch control has been designed to provide continuous behaviour between creep, launch, drive cycles and engagement after shift. The system calculates clutch torque at any given moment according to engine torque, engine speed and trans_mission input speed (calculated back from the wheels’ speeds). After a gear shift, and during a drive cycle, the clutch will not be at a constant fully engaged rest position. The clutch actuator will adjust the clutch travel so that it can transmit slightly more torque than actually delivered by the engine. This provides very fast clutch disengagement times and a smoothing out of indicated peak torque during sudden accelerations by the driver.
Durashift EST enhances the contemporary appeal of the new Fiesta,” Goold said. “Drivers will appreciate its intelligent technology and flexibility, especially those who have ruled out small-car automatics in the past for their sluggish shifting quality and higher fuel consumption.”
Ford's Dependable iB5 Transmission
The latest version of Ford's dependable iB5 five-speed manual transaxle on which Durashift EST is based features a series of enhancements, including new engagement chamfers for ease of gear selection and gear tooth profiles optimised for low gear noise during engine idling. The transaxle and clutch housing also have been revised with additional external ribs. These stiffen the unit for refinement, further contributing to Fiesta’s refined driving quality.
The iB5 unit’s final drive gears and bearings have also been strengthened to boost durability. Shift quality also has been the focus of engineering attention to detail. Double-cone synchronisers are fitted to the first and second gears to minimise downshifting wear.
Fiesta’s transaxle delivers power to the wheels via articulated, equal-length half-shafts. This equal-length configuration reduces the potential for unwanted torque-steer effect when full throttle is applied. The layout also contributes to improved stability under hard acceleration, especially in lane-change manoeuvres or turns.
Low-friction constant velocity plunge joints are fitted inboard. Large deflection spherical ball joints, also friction optimised, are fitted outboard.
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