New Fiat Sedici
4x4 drive system

The Fiat Sedici adopts an electronically-controlled 4x4 drive that distributes variable torque to front and rear wheels. The new on-demand 4x4 system with central differential and 3 operating modes combines the performance of an off-roader with the driving comfort of a road vehicle.

Under normal conditions, the Fiat Sedici system therefore behaves like a transmission with two drive wheels (front ones) with the benefit of lower fuel consumption and lower emission levels. When road conditions decline and grip is lost, the system acts as a 4x4 transmission, automatically modulating torque distribution between the front and rear axle to increase vehicle safety.

The heart of this transmission is an electric dry multi-plate clutch coupling system (operated by an electromagnet) that modulates the transferred torque electronically according to the need for traction. When the ABS sensors detect relative slip between front and rear wheels, an electrical pulse generates the magnetic field to couple the plate and send torque to the slower turning axle (when the AUTO mode is selected, or with LOCK, but above 60 km/h - see below).

This allows the system to change over from a 2WD to a 4WD transmission simply and quickly: all the driver has to do is operate a key on the dashboard to select one of the three operating modes (2WD, AUTO and LOCK) without the need for a separate gear lever.

2WD - With the 2WD function, only the front wheels transmit torque with the 2WD function. The 4x4 is not engaged and there are no dissipation effects. This mode is better suited for normal driving conditions (dry road) and to achieve the lowest possible fuel consumption.

AUTO - In most cases, the torque is transmitted to the front wheels. The distribution of torque between front and rear is controlled automatically. The system supplies optimum torque to the rear wheels when the sensors detect low grip and also to anticipate a loss in traction (e.g. during acceleration).

LOCK - Torque distribution is locked to ensure prompt, stable take-off under extreme conditions (sand, mud and snow). Under these conditions, the torque distribution ratio is 50 to 50 between front and rear axles. This mode is maintained up to 60 km/h and then transfers to Auto mode to ensure a more comfortable drive.

Angles - With its minimum ground clearance of 19 centimetres, the new model can cover uneven, difficult ground, as the ramp angle values reveal (standard A).

Firstly, the rear incidence angle (departure angle, 31.1°), which is the maximum gradient climbable in reverse from a horizontal plane. Next comes the slope angle (ramp breakover angle, 18.1°), i.e. the maximum possible angle at the base of a triangular slope (isosceles) if it is to be driven up without the bottom of the car touching the ground. Last is the front incidence angle (approach angle, 20.3°), a measure of the maximum front angle that may be tackled by an off-road vehicle without the body touching the ground.