Body structure, Electrical systems and Lights

Firm Foundations

Highlights include:
• New standards in torsional rigidity
• Stable platform for excellent noise suppression, handling and crashworthiness
• About 60 per cent of bodyweight in HS/UHS steel
• Second-generation ‘crash boxes’ help prevent body damage
• Multiplex digital signal network for fast control of all major functions
• Powerful screen washing system

The body structures of the 9-3 Sport Sedan and SportCombi are the stiffest yet produced by Saab, providing solid foundations on which their s exemplary handling, ride and safety characteristics are built.

The use of high-grade steels, tailored blanks, laser welding, the galvanizing of all external components and advanced joint techniques has produced extremely strong and durable structures. Effective ‘crash boxes’ in the front bumper help to minimize body damage in impacts up to 15 kph.

The power of the lighting system, which includes the option of bi-xenon headlamps, is in the fine tradition of Saab cars, as is the efficiency of the windscreen wipers and washing systems.

Structural Benefits
Exceptional levels of structural stiffness were an essential requirement in the design of the 9-3 Sport Sedan and SportCombi. It is high torsional rigidity that helps give that reassuring ‘hewn for solid’ feel, which is communicated every time a door is closed or the car negotiates a poor road surface. And it makes a major contribution to eliminating squeaks and rattles, vibrations and resonance.

A stiff body is also a prerequisite for the work of chassis engineers. The car’s handling can only be effectively honed through its suspension and steering if the structure on which all these components exert loadings is solid and predictable.

Finally, but probably most importantly, the car’s ability to withstand a heavy impact is largely due to the strength of its passenger compartment and the ability of the body structure’s crumple zones to prevent energy reaching it.

Structural Strength
The body structure of the Sport Sedan and SportCombi’ is essentially a unitary construction fabricated from steel pressings and beams, on which is mounted a front sub-frame - carrying the engine, gearbox and lower front suspension mountings - and a rear sub-frame, carrying the rear suspension. Although a high level of structural stiffness was an essential requirement, this had to be balanced against the need to reduce unnecessary weight in the interests of fuel economy and achieving responsive handling characteristics.
The Sport Sedan has an exceptional torsional rigidity of 22,000 Nm/degree of deflection, while the SportCombi’s is only 6.6 per cent less than that of the Sport Sedan, despite the extended rear roof and the addition of a large rear tailgate opening. To put these figures in perspective, the body structures are as strong as a meter long rod, fixed at one end, would need to be in order to bend just one degree under the weight of fully-laden large car placed on the other end!

About 60 per cent of the car’s body weight is composed of high strength or ultra high strength steel, most of which is concentrated in the construction of the central passenger safety cage, where all main beams have welded closed sections for additional strength.

In all, about two-thirds of the body parts in the Sport Sedan and SportCombi play a structural role, although the key to the performance of the structure is how all these elements connect and interact in sharing the load-bearing task. The strength of a good design is far more than simply the sum of its parts.

To calculate how loads can be distributed in the most efficient way, structural engineers used CAD techniques and finite element modeling (FEM) with a resolution of up to 850,000 elements, or cells, representing the car’s structure. Each body component is designed to contribute to structural integrity without being overloaded and structure-borne noise radiation from the engine, transmission and suspension is minimized.

Special attention was devoted to the location of seams and joints. It is pointless using high strength steels for different sections if the technique used to join them together is not at least as strong. For example, there are no joints at any of the corners of the safety cage, where stresses are likely to be greatest. Instead, joints between beams are carefully welded in place on straight sections with overlaps of at least 20 mm.

In order to be sure that extra strength does not necessarily mean extra weight, Saab engineers made great use of new technology in specifying ‘tailored blanks’ for large structural components. For example, the two main bearers which extend from the front of the car to the rear bulkhead are made from pressings of high strength steel. These are produced to different thicknesses, according to the localized loading demands at any point in the car’s structure. In other words, the extra strength or weight is located only where it is required.

The SportCombi was designed alongside the Sport Sedan and Convertible so engineers were able to integrate the requirements for a strong five-door body from the very beginning of the 9-3 project. To compensate for the loss of the cross bracing behind a sedan's rear seat, the SportCombi features reinforcement to the base of the C-pillars and the addition of sub-structures or 'rings', each connecting the top and bottom of the C and D-pillars with transverse beams in the roof and across the floor. These 'rings' are then linked longitudinally by two beams in the roof, two in the cargo floor and one behind each side of the rear bodywork.
On both the Sedan and SportCombi there are additional bracings above the rear wheel housings to provide a structure that is more than a match for premium class competitors, despite some potential loss of stiffness through the provision of a split/fold rear seat.

Outer Body
Large single 'monoside' body pressings accommodate inset-mounted doors for good sealing and fine gap tolerances. Substantial ultra high strength steel door beams play an important role in side impact protection. The bottom edges of the doors also overlap and interlock with the strong, reinforced side sills, allowing heavy impact forces to be spread by engaging as much of the neighboring body structure as possible.

To save weight without compromising strength, the hood, rear bumper beam and the tailgate of the SportCombi are made from aluminum

Both front and rear bumper assemblies are designed to be ‘self-repairing’, in that they can absorb impacts up to 8 kph, minimizing damage and the need for repair. The bumper ‘skin’ is simple and quick to replace after a minor collision. For higher speed impacts, Saab was first to introduce deformable ‘crash boxes’ behind the front bumper on the second generation Saab 900 in 1993. These are intended to absorb and contain relatively ‘low speed’ impact forces in order to prevent damage to more expensive bodywork components.

Other manufacturers have now adopted crash boxes but, in the in the 9-3 range, the technique is perfected still further. No less than 103 computer simulations were carried out to ensure their effectiveness; a testimony to the extreme attention to detail that went into finalizing the new structures.

The finished design is an octagon shape with a conical profile and ‘concertina’ sections that will protect the structure of the car, including its front body panels, from damage in impacts up to 15 kph. The boxes are now bolted and only lightly welded to the front beam to make their replacement even easier.

The design of the Sport Sedan’s trunk lid was also the subject of detailed research and the solution adopted is typically Saab. For owners to be able to exploit the load carrying capabilities of a 60/40 folding seat, it was important that trunk opening was as large as possible. That is why the design team chose ‘swan neck’ hinges for the once piece trunk lid

The use of a more conventional strut and multi-link pivot arrangement would have resulted in an unacceptable 15 per cent reduction in opening width, worth 10 cm. The spring-loaded ‘swan-neck’ hinges, in fact, give an even easier, almost ‘weightless’ opening and closing action.

For the SportCombi, the lightly weighted tailgate that opens down to bumper level, its damper rods completely hidden in the roof to allow a clear, uncluttered opening.

Electrical and electronic architecture
The entire electrical and electronic network uses databus transmission, often referred to a ‘multiplexing’. In this way, a CANBUS (Controller Area Network) connects groups of electrical subsystems, using just one or two wires with microprocessors, transistors and LEDs (Light Emitting Diodes) to replace a complicated wiring harness and all its associated relays, switches and bulbs.

CANBUS technology offers great benefits in weight saving, reliability and data transmission capacity. It is used to connect the car’s main subsystems: powertrain, chassis, body, ‘infotainment’, telematics, navigation and climate and comfort.

A battery of sensors are the ‘nerve endings’ of the Sport Sedan and SportCombi and the data they provide is dispatched as packages of digital signals, or ‘buses’, along three information ‘highways’, stopping where required at 44 sub-stations, or microprocessors, for analysis and subsequent action. A powerful control module governs each of these highways and their sub-stations; all three integrated with each other to ensure there are no ‘traffic jams’ or conflicting requirements.

If all this functionality were to be achieved using a traditional, complex wiring harness, it would weigh twice as much, more than 40 kilos, and be twice as long, at 1,600 meters.

A single wire highway, or ‘low speed’ Bus, with a capacity of 33 Kbytes per second, connects functions within the car: the ignition switch, steering column lock, airbags, the main instrument panel, interior lighting, doors, mirrors, windows, security alarm, gear shift position and, where fitted, the sunroof, electrically-operated seats and parking assistance.

Powertrain control, the engine management system, ABS, TCS, ESP and related functions are all connected by a second, dual wire, ‘high speed’ Bus, with a transmission capacity 15 times greater at 500 Kbytes per second.

The third highway is utilized by all 'infotainment' systems, the Bluetooth™ Phone Integration System (BPIS), the GPS navigation system with DVD reader and an advanced voice recognition (AVR) function. These systems are described further in the ‘Interior Design and Features’ section.

The fast moving world of information technology is likely to place increasing demands on the ‘in-car’ time of drivers and passengers and the Saab 9-3 is configured to accommodate all likely future developments in digital communication to and from the car.

Superior Lighting
The strong lighting performance of Saab cars is almost as widely acclaimed as their reputation for safety. Hardly surprising, as good night-time visibility is, of course, an essential element of driving safety.

The Saab 9-3’s headlamps are housed within neatly integrated units, made from molded clear plastic, which is lighter and less prone to stone chips, cracking and condensation than glass.

The standard equipment headlamps use halogen bulbs behind projector units for excellent illumination. Powerful bi-xenon lights are an option for all variants. .These gas discharge bulbs give an extremely bright, much whiter light than halogen units. Saab was among the first manufacturers to offer this technology for both dipped and main beam – hence the term, bi-xenon. Where a normal halogen bulb will emit 1,500 lumens of lighting, a xenon unit will give 3,200 lumens, more than twice as much power, giving a spread of light 60 per cent better.

The effective control of such a powerful beam is essential for the benefit of fellow road users, as well as the driver, and bi-xenon lights have a dynamic, self-leveling function as standard. Under acceleration or braking, sensors detect body motion at the front of the car and electric motors in the headlamp units automatically adjust the height of the beam to compensate for any changes in the attitude of the body. As a further refinement, steering linked bi-xenon lights can also be specified to give an improved field of vision when cornering.

The performance of headlamps, no matter how powerful, is badly compromised if the lenses become caked in grime. Powerful spray jets, working at 3.5 bar pressure, keep the plastic units clean.

At the rear of the car, the single fog light automatically disconnects when the ignition is switched off, an added precaution to prevent it being inadvertently left on when no longer necessary.

The high level rear brake light is an LED unit, as tests show this illuminates more quickly than a conventional bulb, giving a more efficient warning signal.

Cleaning power
Keeping a clear windscreen is vital for driving safety and the large wipers are linked to a powerful battery of three pairs of washer jets, all working under high pressure with twice the power of other systems on the market. It is cleaning power designed to shift the most stubborn of deposits.

In true Saab tradition, the 5.0 liter washer reservoir is exceptionally large, with two liters more capacity than normal. User trials show that jets working at such high pressure do not, in fact, require more washer fluid because they are generally used in shorter bursts.
The windshield wipers are two-speed with an infinitely variable intermittent wipe. An automatic rain-sensing operation is available as an option, including driver adjustment for sensitivity.

Next page: Safety