Auto Car Magazine: Saab 9-3 Sport Sedan and SportCombi Facelifts In Detail

Friday, February 1, 2008

Saab 9-3 Sport Sedan and SportCombi Facelifts In Detail

Page 1: Overview
Page 2: Design
Page 3: Interior features
Page 4: Chassis, Brakes, Steering
Page 5: Powertrain
Page 6: Body structure
Page 7: Safety
Page 8: Security and Operation
Page 9:Ownership and Accessories

Safety

Optimized through Real-life Experience

Crash test configurations based on research
Safety structure with front and rear crumple zones
Second generation Saab Active Head Restraints (SAHR) for front seats
Roof rail airbags for side and severe frontal impacts
Sophisticated sensing for airbag/seat-belt deployment

Saab Automobile AB (Saab) has a long tradition of successful work with vehicle safety. In surveys of real-life collisions made by the US Highway Loss Data Institute (HLDI) and the Swedish insurance company, Folksam, many Saab cars have scored well, several times being ranked best in their segment. In EuroNCAP crash tests, the Saab 9-5 Sedan, 9-3 Sport Sedan and 9-3 Convertible have all achieved a maximum five star rating. In the United State, the 9-3 Sport Sedan is also the first car with standard safety equipment to receive a €œDouble Best Pick rating in crash test conducted by the Insurance Institute for Highway Safety (IIHS).

For Saab, the pursuit of improved safety is a never-ending quest and the Saab 9-3 product program has given safety engineers another opportunity to apply the lessons of real-life safety.

Crash impact resistance benefits from a number of structural systems first seen on the larger 9-5 model and the introduction of additional occupant protection measures, including second generation Saab Active Head Restraints (SAHR) and Roof Rail Airbags.

Crash Configurations

Computer simulations and crash testing at Saab are designed to replicate what happens in real collisions on real roads, based on the findings of a database covering more than 6,100 real-life accidents, including the Saab 9-3 and Saab 9-5, on Swedish roads.

During the Saab 9-3 product development program, the structural design of the car and the deployment of its occupant protection systems were evaluated not only in consumer and legally required crash tests, but also in a large number of additional in-house configurations, taking occupants of different sizes into consideration. Prototype tests were carried out in the laboratory and outdoors in a wide range of speeds and configurations.

However, advanced crash simulations, using finite element methods (FEM) and drawing on Saab's extensive experience, help to find solutions before any prototypes are built. Support by simulation is used throughout the development process in structural design, as well as for the tuning of occupant protection systems, such as seat-belts and airbags. As a result, crash tests are increasingly used as a physical means of verifying what is already known.

Body Structure

The steel safety structure of the 9-3 passenger compartment is fabricated mainly from high strength steel. Most beam sections are completely closed for additional strength and all joints are designed to help prevent tearing under severe impacts.

The front and rear crumple zones are made of carefully shaped steel members designed to help absorb, distribute and deflect impact energy away from the passenger compartment.

Three distinct load paths on each side of the front structure are designed to help channel impact forces through the front sub-frame, along the longitudinal members and through the upper rail into the A-pillar. The longitudinal members have large sections that extend right through the floor of the car as far as the rear seat. This design is a development of the concept first seen on the Saab 9-5.

The three load paths are connected transversely via cross-members, the most important of which is the bumper beam. This helps to distribute impact forces across and through the front structure, to help provide a controlled and predictable deformation in a wide range of frontal collisions. The beam is made from boron alloy steel, up to six times stronger than plain steel with a very high yield strength of 900 Newtons per square millimeter.

To help provide side impact protection, the B-pillar, side sills and door beams behave as a single, integrated structure, increasing the likelihood of deformation in a controlled and predictable way. A key part of this strategy is the pendulum movement for the B-pillar, a concept also used on the 9-5.

In effect, the B-pillar is “hinged from the roof rail of the passenger compartment. It has strengthened upper and middle sections so that, in an impact, it is designed to bend inwards at the bottom, helping to deflect lateral forces downwards towards the floor, away from the more sensitive occupant head and chest areas. The door beams are designed to help support this structure and the bottoms of the doors also interlock with the reinforced side sills so that the entire side structure is designed to perform a load-sharing role.

The door beams are also designed to help provide a major load-bearing function in side impacts against narrow objects, such as a tree or telegraph pole, when the B-pillar is not engaged.

At the rear, two more longitudinal members are designed to buckle and deform in a progressive manner to help protect the passenger compartment in a rear end collision. They also assist in dissipating crash energy towards the C-pillars. The fuel tank is mounted low down in front of the rear axle, away from any likely point of impact.

Second Generation Saab Active Head Restraints (SAHR)

Saab Active Head Restraints (SAHR) are fitted as standard to the front seats. Crash investigation findings published by the US Journal of Trauma, and comparative tests by the US Insurance Institute for Highway Safety and the Thatcham insurance research center in the UK, have shown the SAHR to be extremely effective in helping to prevent serious neck injury to front seat occupants in the event of a rear-end collision. The Journal of Trauma published a Saab study that found a remarkable 75 per cent reduction in severe neck injuries when comparing Saab cars fitted with SAHR against older Saab models not equipped with the SAHR system.

The Saab 9-3 product line features a “second generation version for even faster activation in rear impacts at lower speeds. The head restraint is activated as soon as the occupant's lower back is pressed into the seatback by the effect of inertia during a rear impact.

The restraint is fixed to the top of the seat-back frame, which is designed to pivot at its mid-point. As the occupant lower back comes into contact with the bottom of the seatback, the upper half of the frame carrying the head restraint is designed to move forward and upward, towards the occupant's head. In a rear end collision, this mechanism helps prevent neck injury by reducing the amount of head movement relative to the torso.

The SAHR system is entirely mechanical and after activation the head restraint automatically springs back to its passive position, ready for future use.

Roof Rail Airbags and Front Side Airbags

Roof-mounted airbags are installed on each side, between the A and C-pillars, in the interior headlining above the side windows. These are designed to help provide head protection for both front and rear seat occupants throughout an entire crash sequence. Side airbags, mounted in the outboard edges of both front seatbacks, are designed to help provide thorax protection.

Both are activated in side impacts, together with seat-belt pre-tensioning, and also in severe frontal impacts which require stage 2 activation of the front airbags. This helps provide head and body protection in the event of any subsequent secondary impact or an eventual roll.

To improve cushion kinematics during inflation, the roof rail airbags are inflated outwards from the central B-pillar area. They remain inflated for up to three seconds in order to help prevent an occupant's head striking the A, B, or C-pillar, or intruding exterior objects, during the course of an impact sequence.

For sophisticated impact sensing and “intelligent airbag deployment, there are two impact sensors in each side of the car, one in the sill near the B-pillar and the other in the lower part of the C-pillar. These sensors measure acceleration rates, a decision on airbag deployment being taken by the central sensing and diagnostic module (SDM) in a few milliseconds.

Dual Stage Front Airbags

These are designed to help provide an 'occupant-friendly' deployment in frontal impacts.

Two sensors in the front bumper beam detect impact severity, a sensor in the seat track communicates the seating position and a switch in the seat-belt buckles indicates whether or not the belts are being worn. This data is sent to the centrally located SDM which, within milliseconds, chooses between activation of the belt pre-tensioners alone, or in combination with stage 1 or stage 2 inflation of the airbags. In a severe impact, where stage 2 of the front airbag is used, the roof rail airbag is also designed todeploy for additional head protection.

A collision with a relatively low level of impact energy would, for example, likely require less airbag pressure and, therefore, a slower rate of inflation than a more severe, high-energy impact. A short driver sitting close to the steering wheel also benefits from a softer, lower pressure inflation.

Seat-belt Load Limiter and Reminder System

Despite the use of airbags, seat-belts are still the single most important occupant restraint system and three-point belts are provided for all seating positions, including the middle of the rear seat.

For both front occupants, there are belt pre-tensioners and load limiting functions to help remove belt slack and reduce belt loads in more significant collisions. The pre-tensioner is mounted on the belt retractor and is activated by a signal from the airbag sensing system, igniting a small pyrotechnic charge that retracts the belt.

The load limiting function consists of a torsion bar inside the retractor that, at a pre-determined load level, will start to deform helping to reduce the belt load.

Saab has used a seat-belt reminder function since 1974 and, to further emphasize the importance of belt usage, the system in the 9-3 range independently informs and reminds the driver and the front passenger of non belt usage.

Occupant-friendly Interior

A great deal of experience has gone into making the interior surfaces and materials more “occupant-friendly. In particular, the front areas of the cabin near the knee and lower leg are well bolstered to help prevent occupant injury. The driver pedals are designed to break away in a severe impact and the steering column is also collapsible.

Passenger safety is the main reason why interior door armrests and inner door handles are recessed. It is also one of the reasons why the Saan 9-3, in common with most other Saab cars, has a floor-mounted ignition switch, well away from sensitive knee and leg areas.

Driving Safety

It is, of course, preferable to be abler to avoid becoming involved in any road collision. Here the 9-3 excellent chassis dynamics, steering and brakes helpkeep the driver in control and, therefore, less likely to be involved in, or better able to avoid, a collision.

Driving safety is also advanced by the availability of anElectronic Stability Program (ESP), Mechanical Brake Assistance (MBA), Electronic Brake force Distribution (EBD), Cornering Brake Control (CBC). These features are described in the Chassis section.

Optional cornering bi-xenon headlights provide better night vision. The steering-linked bulbs can swivel up to 15 degrees when negotiating a bend or corner above 15 kph. In highway driving above 120 kph, the low beam is also automatically raised slightly for improved illumination without dazzling on-coming drivers.

Improved driving safety also involves reducing the potential for driver distraction and the 9-3 features Saab ComSense functionality, which uses the concept of 'dynamic workload management'. This is described in the Interior Features section.

A further aid is the optional Tire Pressure Monitoring System (TPMS). This warns the driver if pressure in any of the tires drops below the recommended level. Sensors in the valves initiate a radio signal and a warning message is illuminated in the main instrument display. TPMS is an option for Aero variants and comes as standard when 18-inch wheels are specified.