9-5 Bi-Xenon Headlamps



SAAB BI-XENON LIGHTING SHOWS CLEAR BENEFITS

NORCROSS, Ga. - Strong, powerful lights have always been a Saab specialty. The performance has partly been due to the engineers' own survival instincts - you need a good spread of light when you're peering through the gloom and murk of a Swedish winter. No wonder Saabs win car-magazine lighting tests - even against xenon-equipped rivals. It's all part of Saab's inherent safety culture.

So far, though, all of this has been achieved with conventional halogen-bulb technology. But that's about to change: bi-xenon lights are now available as an option on the new Saab 9-5 Arc and Aero models. And the results are bright, indeed. The light spread is 60 percent better than with Saab's already exemplary halogen bulbs, and the light output is double. Which means there's a far greater chance of spotting a moose that's about to wander out of the Swedish mist and onto the road.

What is bi-xenon lighting?

Unlike conventional halogen bulbs, which use a glowing filament and reflectors to direct the spread of light, xenon lighting uses a bright, white gas-discharge lamp. Xenon lights work on alternating current (AC) while halogen bulbs are powered by the battery's DC current. To provide the xenon lights with AC, an electronic ballast (starter module), with a high-voltage start-up, transforms the normal voltage into AC. This provides significantly more power for lighting.

Until relatively recently, only low-beam xenon light systems have been on the market. They used a combination of xenon lighting with its projector modules for low-beam work and halogen bulbs with reflectors for high-beam situations, simply because the xenon projector modules just weren't big enough to work effectively on high beam.

However, two years ago, the first bi-xenon lights were made commercially available, with a projector module featuring a shutter which rises to reveal the whole lamp on high beam. That's when Saab decided to incorporate the lighting system as an option on the new Saab 9-5. However, the bi-xenon headlamp unit still retains halogen bulbs with separate, larger reflectors for the headlight flash function, an important safety feature.

Saab's goal - a world-class lighting system

"It was a very exciting time for us," explained Ingemar Knutson, manager of exterior lighting systems. "We had the opportunity to create a world-leading lighting system on the new 9-5 range, using a xenon gas-discharge lamp both on low and on high beam. We are one of the first with such a system.

"We worked very closely with exterior designer Ola Granlund to ensure that we had enough surface area to make the bi-xenon lights work really efficiently. It's really important to use your source in the right way - if you have very slim lights then you don't have very much surface area to make the reflectors work properly. Sure they look good, but then they don't do the job well enough."

World-leading safety standards are at the core of Saab's philosophy for building motor cars. Comparing the light output of a halogen lamp to a bi-xenon lamp shows the difference. The Saab halogen bulb throws out 1,500 lumens - the lumen being a measure of light. The bi-xenon doubles that to 3,000 lumens.

Xenon light is also a white light - unlike the yellow cast from a halogen bulb - with a terrific spread, allowing the lights to illuminate to the sides where trees meet the edge of the road. The white light also benefits someone who may suffer deteriorating night vision, which starts to become more prevalent in older people.

Development of the bi-xenon lights

Saab worked closely with lamp supplier Valeo to develop the necessary performance required by Saab's engineers.

Among the issues to be resolved was the necessity for a dynamic self-leveling system, so the lights wouldn't affect other road users as the car body travels up and down over road imperfections. Sensors are connected to the front and rear axles and obtain information from the suspension system on compression rates. This information is fed to a motor which reacts in milliseconds so that the reflector shades the bulb. The bulb itself remains fixed in position.

There's also a system of electronic "filters," so that the motor can correctly understand the information it receives, otherwise the shade would be constantly in motion to no benefit.

Initially, Valeo made photometric prototypes for laboratory testing. These prototypes were then tested and measured on the road, using a special bumper fitted with the lamps, before moving to the final prototype stage and then on to series production.

"We have our own internal Saab scale for assessing lamps," Knutson continued. "We look at all the small details - I really believe that's what makes us the best. On a scale of 0 to 10, a good lamp will register seven. When we started with bi-xenon it was only at four. By the time we finished, it was up to nine - that's how good it is."

High-pressure spray for new clear-lens design

Bi-xenon lamps have necessitated using clear plastic lens covers. While looking more modern and contemporary, the new clear-lens philosophy has meant dealing a blow to one of Saab's safety landmarks: the headlamp wash/wipe system. Saab was the first car manufacturer to introduce this - on a Saab 99 in 1971 - and the benefits of clean headlamps in poor driving conditions were plain to see.

The new clear plastic covers are more resistant to stone chips and breakage as well as being lighter. A headlamp with a plastic lens is also better for avoiding condensation than one with a glass lens. The plastic lens gets warmed up in a more efficient way to dry the condensation. Because this plastic lens would be scratched by the traditional wash/wipe system, the headlight cleaning job is now done by high-pressure jets which rise from the bumper to spray cleaning fluid over the lens covers.

But here, too, Saab engineers have done a really thorough job on the system. "There's a legally prescribed 'dirt' you have to use to measure the washers' performance," explained Knutson. "You then have to go through a dirt/wash cycle and measure the deterioration of the light output. Which, of course, we did. But we also went and found some real mud. Swedish mud. And tested the system properly. Because if we weren't going to have a wash/wipe system, then we had to have really powerful jet sprays that worked in a Swedish winter."

The Saab jet sprays now exceed the legal requirement in Sweden by 15 percent "I think we have a lighting system that is truly world class," Knutson concluded. "It's the result of our focus on real-life safety strategies. We have to make Saabs work, and work well, even in the most extreme conditions. And often that means in Sweden!"


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