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CitroŽn C3 SensoDrive gearbox


An electronically controlled manual gearbox, the SensoDrive features electronically managed clutch and gear-shift functions. As a result, the car has no clutch pedal and the gear lever - which remains present - has no mechanical link with the gearbox.

The SensoDrive gearbox is managed by a control unit, which controls two actuators. One actuator changes gears while the other, which is equipped with a facing wear compensation system, opens and closes the clutch. The gearbox control unit also dialogues with the engine control unit.
Linked to the C3's multiplex electrics (CAN network), the gearbox control unit manages all the functions linked to the SensoDrive gearbox: start-up, automatic mode, safety functions, instrument cluster display. It diagnoses any operating failures and switches to degraded operation where necessary.

This sophisticated electronic management system takes into account all the parameters necessary for efficient gear-changing: gear lever, accelerator, brake, engine and gearbox rpm, vehicle speed, ABS, ESP, engine torque and temperature.

In this way, when the gearbox control unit receives an order - in either operating mode - to change speeds, it briefly cuts off the engine's power flow, disengages the clutch, changes gears, engages the clutch and authorises power to be restored. These operations are sequenced as quickly as possible to minimise the break in acceleration.

For vehicle start-up, the gearbox control unit closes the clutch in accordance with the accelerator position and the engine speed. With this high-precision servo system, the driver remains in full control of the car in the most difficult situations [reverse parking, hill starts) as well as on fast starts.

In automatic mode, gears are selected by the computer on the basis of the auto-adaptive shift patterns. The control unit analyses the driver's behaviour and the type of route (rising, falling, corner) as well as the vehicle load and surface grip in order to define the most appropriate gear speed. The SensoDrive gearbox reaps the benefits of the experience acquired by PSA Peugeot Citroen with the auto-adaptive gearbox.

To avoid changing gears too frequently, gear shifts are conducted at different speeds during acceleration and deceleration.

On C3 models equipped with ESP, the SensoDrive gearbox takes account of the ESP to initiate gear shifts and ensure optimised vehicle operation in all situations.

© 2002 Julian Marsh/Automobiles CitroŽn SA