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The C4 with a 6-speed electronic gearbox system

Premiered on the C4 and mated to the HDi 110 DPFS engine, the 6-speed electronic gearbox system is of an entirely new design.
This highly driveable engine boasts a range of advantages. Electro-hydraulic gearbox control makes for smooth, fast gear changing.  At the same time, automated gear and clutch management cuts fuel consumption by between 3% and 5%, compared with a conventional manual gearbox.
This new gearbox therefore provides a real alternative to manual and automatic transmissions, not only in terms of driveability and comfort, but also in terms of fuel economy and a particularly attractive customer price. It joins the long list of innovative equipment available on the C4, for safety, convenience and on-board comfort.
A vehicle of innovative design and features that has picked up an array of prizes (including "World Car Design 2006" at the recent New York International Motor Show), the C4 is enjoying considerable market success. More than 350,000 vehicles have been sold to date.

The C4 HDi 110 DPFS equipped with the new 6-speed electronic gearbox system will be available from June 2006.

By means of automating gear changes and clutch control, this new gearbox obtains a reduction of fuel consumption on the order of 3 to 5% in comparison to a conventional manual gearbox. Fuel savings are boosted by the presence of a 6th gear.
Due to its particularly fuel-efficient engine, the C4 HDi 110 DPFS with the six-speed electronic gearbox system thus brings fuel consumption down to 4.5 litres per 100 kilometres in a combined cycle, with CO2 emissions of 120 grams per kilometre.
The six-speed electronic gearbox system offers outstanding user comfort and responsiveness to the driver’s commands. Its electro-hydraulic control system ensures smooth and lightning-fast gear changes in a wide range of transmission ratios, which makes driving with this gearbox particularly pleasant.
The new gearbox permanently adapts to the driver’s behaviour and reinforces his driving sensations in sports mode, which makes gear changes even faster. It also offers him peace of mind and driving comfort with the hill-hold control and easy acceleration dosage when manoeuvring, particularly in reverse.
The six-speed electronic gearbox system offers a real alternative to conventional automatic or manual transmissions – by the driving pleasure it procures as much as by the fuel savings it generates and its attractive price.
This new gearbox expands the offer of automated manual gearboxes already available in the CitroŽn range. These are proposed in combination with petrol and diesel engines in the C1, C2, C3 and C3 Pluriel models. Since its introduction in 2002, 130,000 of these subcompacts were sold with the automated manual gearbox SensoDrive.

DRIVING PLEASURE IN MANUAL MODE AND IN AUTOMATED MODE
The electronic gearbox system gives the driver a choice between two driving modes:

  • a manual mode in which he retains full control over gear changes by using the shift paddles behind the steering wheel or the sequential shift lever.

  • an automated mode in which the gear selection is managed by the gearbox control unit.

At any time, the driver can switch from one mode to the other, depending on his preferences and his environment: main road, motorway, city, traffic jams.

Driving without constraints in manual mode
By activating manual mode, the driver decides at which moment he or she wants to change gears, while at the same time benefiting from the absence of the clutch pedal.
The driver is permanently informed about the selected gear by the information displayed on the instrument panel.
He or she can change gears with the help of two types of controls, which are perfectly substitutable:

  • Shift paddles behind the steering wheel
    The right-hand paddle is used to change up, and the left-hand paddle to change down. These paddles give access to the six forward speeds. For maximum comfort and safety, the paddles are fixed, irrespective of the position of the steering wheel.

  • The sequential lever
    On the shift gate, the manual mode is indicated by the letter M, accompanied by the signs + for changing up and – for changing down.

For safety reasons, only the shift lever can be used to put the car into neutral (N) or reverse (R). The reverse gear is available when the vehicle is moving at less than 3.5 kph.
The shift lever has stable positions which indicate to the driver the operating mode chosen – at the same time, this mode is always displayed on the instrument panel.
But even when the driver selects the manual mode, the automated manual gearbox ensures a high level of driving comfort.
When the car slows down and stops (for example, when approaching a stop sign or a traffic light), the gearbox changes down automatically until it reaches 1st gear.
Automatic downshifting is a function of several criteria that are managed by the control unit (insufficient engine speed, slope, sporty driving style, etc.).
The gearbox control unit also facilitates downshifting by increasing engine speed to make gear changes smoother and without jolts. 

Stress-free driving in automated mode
In the automated mode, gear changes are managed electronically in order to optimise driving comfort and fuel consumption.
This mode is activated by placing the lever in position A on the shift gate. If the driver opts for this driving mode, the AUTO symbol is displayed on the instrument panel, together with the gear engaged.
The gearbox control unit then selects the gear that is best suited according to the auto-adapting shift patterns that are determined as a function of the driver’s behaviour, the road type, engine rpm, vehicle speed and grip conditions.
The system thus prevents situations in which engine speed is too high or too low and proposes an economical shift pattern aimed at lowering fuel consumption. Optimised gear change management produces fuel savings on the order of 3 to 5% in comparison to a manual gearbox, depending on driving cycles.
However, certain specific situations are immediately recognized and taken into account by the gearbox. These include holding the engaged gear in phases of sustained acceleration, downshifting when the car is re-accelerating and holding the gear or downshifting to assist the motor brake.
If the driver wants to take control of the gearbox while driving in automated mode (for instance in an emergency situation or while overtaking), he can do so immediately. He merely needs to touch one of the paddles, and his shift request is taken into account by the gearbox. If no additional manual command is issued by the driver during a short period thereafter (approx. 20 seconds), the gearbox switches back to automated mode.

ENHANCED DRIVING COMFORT, FUEL SAVINGS AND PEACE OF MIND

Six speeds for more drivability and lower fuel consumption
The presence of six speeds in the electronic gearbox system enables it to make optimal use of all the qualities of the engine and guarantees, in both manual and automated mode, perfect responsiveness and smooth operation of the gearbox as well as reduced fuel consumption and optimal acoustic comfort.
The design of the automated gearbox facilitates the use of these six speeds by the driver:

  • In manual mode it is sufficient to apply pressure to the paddles (or to flick the shift lever) to shift to the desired gear. Changing gears no longer requires successive moves of the shift lever or repeated clutch work.
  • In automated mode, the gearbox makes optimal use of the 6th gear to increase fuel savings.

Electro-hydraulic controls for smooth and speedy shifting
Due to the use of new electro-hydraulic actuators, the six-speed electronic gearbox system makes shifting gentle and smooth in both manual and automated mode.
Smooth shifting (with virtually no jolts) is not obtained at the expense of shifting speed. The six-speed electronic gearbox system reconciles both and distinguishes itself by the speed with which it manages gear changes.
The time for a gear change is:

  • 0.8 seconds for changing a gear in manual mode,
  • 1.2 seconds for changing a gear in automated mode.

In addition, the six-speed electronic gearbox system offers precise and easy dosage of acceleration during manoeuvres, particularly in reverse. The accelerator responds quickly to all demands, smoothly and without jolts.

A sport mode for even more responsiveness
The six-speed electronic gearbox system of the C4 also offers a sport mode. This mode, which is available with both manual and automated operation, constantly favours fast gear changes. The total time required for shifting is thus brought down to 0.4 seconds in manual mode and 0.5 seconds in automated mode.
In automated mode, the sport mode is obtained by implementing specific shift pattern: upshifts and downshifts are triggered at higher engine speeds than in normal operation.
The sport mode is activated by the S button on the shift gate. Once selected, an S is displayed on the instrument panel.

Hill-hold control for more safety
For improved safety, the C4 with six-speed electronic gearbox system is equipped with a hill-hold control that facilitates starting off on a slope.
On a slope, the control holds the vehicle for two seconds after the driver has taken his foot off the brake. It thus makes it possible to safely accelerate the car when starting off or manoeuvring on a slope, and to re-start the car without any stress.
The ESP activates the hill-hold control and temporarily keeps the brakes applied when the driver takes his or her foot off the brake to accelerate.
This assistance is provided when starting on an uphill or downhill slope, both in forward gear and in reverse, and the hill-hold control is activated on slopes with a gradient of 3% and higher.