What are bi-function halogen projector headlights

12 headlight systems put to the test: Through the night with Lux eyes

Anyone who has ever switched from a car with a good xenon or LED system to one with a simple halogen light knows this feeling: It is as if two candles were burning instead of two powerful headlights. Both color, brightness and range are less than modern headlights. No wonder that xenon systems are now already available in small cars, while the luxury class is already moving towards full LEDs. But which technology is really worthwhile? auto motor and sport has intensively examined twelve systems in the Hella light tunnel and during extensive comparison drives.

Halogen light dominates the low price class

Halogen headlights continue to dominate the inexpensive vehicle classes. With the Dacia Sandero, there is even no alternative. The technology is tried and tested and inexpensive, the headlights send the light onto the road either via reflectors, as in the Dacia, or via projection lenses. As a rule, the incandescent lamps are easy to replace, even with brighter retrofit lamps: auto motor and sportTests have shown that those with a pair price of 30 euros noticeably improve the performance of the headlight. This would also do the Dacia good: the low and high beams shine yellowish, spotty, streaky and with a short range - so gloomy, as if one of the two were defective.

Xenon light with plus in brightness

Models with xenon light illuminate the road significantly better. It is not generated by a glowing filament, as is the case with halogen, but by an arc between two electrodes in the torch. A high-voltage pulse of up to 25,000 volts is required for ignition, after which the gas in the piston heats up until the operating temperature and resistance are reached. Several seconds pass before it reaches full brightness.

Simple versions like the Hyundai i40 combine a xenon bulb for the low beam with a halogen headlight for the high beam. The problem with this is the different light color and intensity, which makes putting on the high beam on the Hyundai appear inharmonious. Its pure halogen counterpart therefore appears only marginally worse. With the Bixenon, as it has the Fiat 500, a flap in the module is used to switch between the operating modes. In addition, the Fiat offers a halogen headlight for the high beam. This looks a bit emphasized in front of the area, so it gives a lot of light around 20 meters in front of the car, but achieves a decent range. The low beam looks a bit yellowish and streaky, with a sometimes annoyingly hard cut-off line on hilltops and in curves. With the 35 watt xenon systems, automatic headlight range control and a headlight cleaning system are required to prevent others from being dazzled.

Good range in the Beetle despite fewer watts

This is different with the 25-watt system in the VW Beetle. Its xenon burner develops 2,000 instead of 3,000 lumens of light output, which means that neither headlight range adjustment nor cleaning systems are required, which saves costs. Nevertheless, its low beam shines brightly and surprisingly homogeneously, the high beam with a decent range, albeit with a slightly reduced brightness and spread compared to good 35-watt systems.

One of these is that of the Opel Mokka. Its bi-xenon adaptive light illuminates the road evenly, offers a solid range and light functions that adapt it to the driving situation. Some of them - such as the play street light - can only be guessed at. The advantage of the Mokka: its higher installation height of the headlights, which is typical for SUVs, which improves the emission efficiency. Recognizable on the Volvo V40, whose headlights are mounted twelve centimeters lower. In addition, it is annoyed by shadowing from the hood, which is pulled far forward - a tribute to design and pedestrian protection.

LED offers a lot of light in a small space

Also driven by design: the trend towards full-LED headlights (LED: light-emitting diode). The biggest advantage of LEDs is their small footprint in relation to the light output. Several light-emitting diodes are closely combined to form modules, so-called LED arrays, which require significantly less space than halogen lamps or xenon burners. This not only makes the headlights more stylish, but also enables complex lighting functions to be implemented in the smallest of spaces in the future. Wherever panels and rollers still move, in the future it will be controlled exclusively by electronics. Another pro-argument is the so-called color temperature, which comes closest to daylight (6,500 Kelvin). If halogen shines with around 3,200 and xenon light with 4,200 Kelvin, LEDs create 5,500 Kelvin. The advertised lower energy consumption is only partly correct, however. Because what the LEDs save through their efficiency is used again for electronics and cooling by means of fans.

Not too clear a head start for LED technology

The Audi A7 also ventilates its full LED units, which provide bright, uniform light with a pleasant color, but a range that is not outstanding compared to xenon. The range of functions is also limited: If the adaptive xenon light with maskable high beam at Audi even takes into account data from the navigation system for the situation-appropriate leveling of the headlights (e.g. at intersections), LED can only handle turning, motorway and - albeit very good - all-weather light. In any case, the fog light of the BMW 650i is more dazzling, and the low beam is also displeasing due to its uneven distribution in the range of up to 20 meters. If you look closely, you can even see the individual light chips. The light becomes better in the distance, although the range of the high beam with its pleasant light tunnel could also be greater.

When switching to the Lexus GS, its light color is immediately noticeable. It arises at the edges of the individual lenses, where the light shimmers in rainbow colors - annoying in the light channel and in the practice. On the road, the bright Lexus LEDs shine imposingly, but not as balanced as the elaborate mixed system of the Mercedes CLS with projector, reflector and swivel mechanism. It not only raises the high beam gently, but also offers the most effective adaptation to the shape of a curve. So the Mercedes brings its relatively harmonious and powerful LED light optimally onto the road - and thus a narrow test victory.

Very good light for 760 euros

Even if the Hyundai halogen light works properly - if you are often out and about in the dark, you should treat yourself to Bixenon. The VW Beetle shows what a good and still cheap solution (760 euros) looks like. The adaptive light of the Opel Mokka is similar to the masking function of the Golf-Bixenon. The full-LED headlights in the luxury class shine brightly similar to daylight, but have some catching up to do in terms of range and light functions compared to the top solutions for xenon.