Car Design News: Fiat Bravo: In Depth

Class-beating safety

Fifteen thousand hours of calculation, 60 crash tests, one hundred and fifty simulation cycles with a HyGe sled, and one hundred tests on components and subsystems. These figures underline the company commitment to making the Bravo one of the safest cars around, not only in its segment but on the entire car market, because the model is state-of-the-art where passive safety systems are concerned.

Total protection, in other words, which starts with the devices that are dedicated specifically to safety: as many as 7 airbags, three-point seat-belts with pre-tensioners and load limiters, five head-restraints and the FPS fire prevention device. Then the new chassis, which was designed to absorb any impact very effectively. And finally, the contribution made to the protection of occupants by the bodywork, the bonnet, doors and facia crossbeam. Nor can we overlook the contribution made to passive safety by other elements such as the seats or the steering column, which were designed taking their behaviour in an accident into consideration.

The Air-Bag Smart 2 system

Complete protection, intelligent protection. In a head-on impact, occupants are protected by an innovative restraint system known as 'Air-Bag Smart 2', because it automatically adapts the activation parameters to the severity of the accident. Starting from the driver front airbag, which adopts a different logic from conventional airbags. Until now, when the airbags were activated, they inflated simultaneously up to their maximum limit, which was established to safeguard occupants during severe impacts. The Fiat Bravo, on the other hand, adopts a driver front airbag with dual-stage activation; this means that the system only activates the first of the two stages when the impact is of moderate strength, but activates both in the event of a more serious collision. The two stages can also be activated with different sequences depending on the type of impact. In any case, the bridles inside the bags guarantee that the maximum dimensions and the shape taken by the cushions are as non-invasive as possible for passengers. The front passenger airbag can obviously be de-activated (using the menu on the control panel), to carry a child in a safety seat facing backwards on the front seat (the pre-tensioner on the other hand remains active).

The sensors of the 'Air-Bag Smart 2' system also control the activation of the seat-belt pre-tensioners. The Bravo is fitted with front seat-belts that are each complete with an inertia reel, pre-tensioner and load limiter. On impact, the electronically controlled pyrotechnic pre-tensioner retracts the belt in a few milliseconds, so that it adheres perfectly to the body. The load limiters are positioned inside the inertia reels, and they yield in a controlled manner, metering the force exercised by the belt on the shoulder of the person wearing it. And finally, the front protection system of the Bravo offers the option of an airbag under the steering column, to render this area, traditionally the most dangerous for the knees, inoffensive.

The control unit and the sensors

The Fiat Bravo is fitted with all the most advanced passive safety devices available today. A sophisticated 'nervous system' has been developed to manage them, governed by an electronic control unit in the front tunnel. This system receives the signals from the various sensors positioned around the car (in addition to those inside the system itself), and on the basis of these signals decides how many and which devices to activate. This is why the system behaves in an 'intelligent' manner. It is not activated when, in spite of an impact, there is no danger that an occupant will collide with the surfaces of the car. It recognises stress that does not derive from a collision, and continues to function even if there is an electrical blackout. This is all made possible by particularly sophisticated functioning logics and detection terminals. Such as the CSA (Crash Severity Algorithm), which recognises the severity of an impact and controls the front airbags, or the sensor that detects the presence of a passenger, and can warn the occupant to fasten his seat-belt, by a beeper or a telltale on the instrument panel. Or the ECS (Early Crash Sensor), the decentralised sensor that measures head-on impact, an additional device positioned in the front of the car, that enables the control unit to anticipate the activation of the front airbags; this allows the airbag to be completely inflated before the occupant has even begun to move forward towards the steering wheel or facia, unlike a conventional system.

Curtain-bags and sidebags

The former are airbags that descend down the windows to protect occupants heads in the event of a side-on collision. The curtain-bags adopted on the Bravo are more protective than other systems (because they always take up the correct position), faster to inflate and less invasive for passengers. They open from the top down and there is no risk of their causing secondary injury to the occupants arms with their movement.

They also effectively protect the heads of both front and rear passengers, because they extend the whole length of the side windows, protecting occupants even if the car overturns. The two bags (one on each side) are positioned under the longitudinals of the roof, folded inside a closed compartment. At the appropriate moment, the cover bends to allow the bags to inflate and to descend.

And finally, to protect the pelvis and chest of passengers even if they hit the sides of the car, the Fiat Bravo also fits sidebags inside the seat squabs, where they protect the occupants best, regardless of the latter stature or position, or how the seat is regulated.

More stringent tests for total protection

The experts at the Fiat Safety Centre at Orbassano (outside Turin) subjected the Fiat Bravo to all possible types of high speed collisions in order to verify the effectiveness of the integrated protection system developed for the new model on the spot. They then analysed the results on the basis of the structural and biomechanical parameters envisaged by some of the world most stringent legislation. The following results were obtained.

Head-on impact

The Fiat Bravo achieved excellent results in two different types of tests. The first was performed at a speed of 64 km/h against a deforming barrier which simulates a head-on impact between two cars; the second envisages a crash at 56 km/h against a fixed, rigid barrier. Thanks to the robust structural architecture and the use of highly energy-absorbing materials, the intrusion levels measured on the Bravo during these tests were very low and allowed all the doors to open, without generating significant inertia stress on occupants, because this was efficiently absorbed by the Smart Air-Bag system. And finally, in the case of head-on impact, the items carried in the Bravo luggage compartment do not hit passengers.

Side-on impact

Two tests recognised internationally bear witness to the new model ability to guarantee the safety of front and rear passengers, even in the event of a high speed side-on collision. The first is 'Impact against a deforming barrier'; the Bravo reacts superbly to this test, which simulates a collision at 50 km/h between two vehicles at a 90� angle, thanks to the protection offered to the pelvic area by the robust bodyshell structure, to the abdomen and chest by the combined action of the sidebags and door panels, and to the head by the curtain-bags. The second test is 'Side-on impact against a pole', one of the most dangerous for motorists.

Rear impact

During rear impact tests, attention is focused, in structural terms, on containing the deformation of the passenger compartment and on preventing any damage to the fuel tank, which could cause a fire. What is more, from a bio-mechanical viewpoint, efforts are concentrated on guaranteeing that the seats support the occupant well without collapsing, and on minimising any injury, particularly to the neck and head, which are usually the most vulnerable parts of the body.

Protection of pedestrians

The styling of the front part of the Fiat Bravo was developed bearing the protection of pedestrians in mind. The volumes are smooth and rounded, and there are no sharp edges that could injure pedestrians. The large surface of the bonnet minimises the risk that a pedestrian could hit the front uprights. The sturdiest components in the engine bay are positioned at a suitable distance from the bonnet, to allow the 'skin' of the bonnet to absorb the energy deriving from impact with a pedestrian head.

Protection of children

The new model also features all the devices that guarantee absolute safety for children travelling in the car. The most important, and most effective, of these are the Isofix attachments on the rear seats, and the de-activation of the front passenger airbag by the onboard computer.

Protection against fire

From the bodyshell down to the smallest component, the Fiat Bravo was designed and built to meet Fiat latest, and strictest, internal fire prevention standards. For example, the Fire Prevention System which instantly cuts off the electric pump on petrol-engined cars and the fuel supply solenoid on diesel models, in the event of serious impacts. The switch is positioned under the lining of the right front door pillar, while the plastic fuel tank, which already meets future legislative requirements, is positioned where it is protected in a collision, and built to resist deformation with no loss of fuel.