Retrofitting Xenons (HID) Lighting to reflector housings

Retrofitting Xenon or High Intensity Discharge (HID)  lights to replace the standard halogen reflector setup may seem like a good idea and a whole lot cheaper than paying the $1000-2000 premium for the factory Xenons / Bi-Xenons but in reality not only is it illegal but not a very wise move.

Firstly there are a number of different ways to deliver light, lens optics, reflector optics and projector (polyellipsoidal) however only the latter two are still used.

Reflector lamps which are used by the majority of cars and the other is a projector lamp which are used by cars with Xenons and some cars with Halogen globes.  Projector housings have a few drawbacks and one is that there is a very sharp cutoff of light and the other is that due to the optics used some light is lost so using them with Halogen can result in a drop in light output. Some older cars came from the factory with Xenon’s fitted to a reflector housing but they used a bulb designed for this application and the reflector shape was designed for the Xenon however they still suffered from some light scatter.

Problem 1. Light scatter

The biggest problem is glare and blinding oncoming traffic, the reflector is designed for use with Halogen and not Xenon and you end up with a lot of scatter as the diagram below demonstrates. You could have a light source that measures 10,000 lumens but it would be useless because of poor reflector design, to utilise Xenon correctly you need to use a projector lense hence why every car on the market with an OEM Xenon / Bi-Xenon option uses projectors.


Xenon globes can output up to three times the light of a Halogen globe, this is a key issue with these retrofit kits as the reflector on the left is a standard reflector and the design is to send the light in one direction with some scatter whereas the projector housing on the right is designed to focus all the light on the projector lense, a cut off shield prevents most of the glare and gives the sharp cutoff.

With much of the light being scattered the performance of Xenon’s is generally nowhere as good as that of Halogens, the improvement that is seen is a lot more light in front of the car but a lot less in the distance on the road where you need it. Daniel Stern sums this up well “It’s tricky to judge headlamp beam performance without a lot of knowledge, a lot of training and a lot of special equipment, because subjective perceptions are very misleading. Having a lot of strong light in the foreground, that is on the road close to the car and out to the sides, is very comforting and reliably produces a strong impression of “good headlights”. The problem is that not only is foreground lighting of decidedly secondary importance when travelling much above 30 mph, but having a very strong pool of light close to the car causes your pupils to close down, worsening your distance vision…all the while giving you this false sense of security. This is to say nothing of the massive amounts of glare to other road users and backdazzle to you, the driver, that results from these “retrofits”.” (see link below)

At this point hopefully you’re having second thoughts about fitting that cheap chinese Xenon kit you won on the online auction site but don’t dispair because purchasing a projector housing could give your Xenon/HID lighting without blinding other users.

Problem 2. Colour of the globe

The colour of the globe (known as the kelvin) is often marketed as the bluer the better by the sellers of the kits, nothing could be further from the truth as the following shows.

Here are some light outputs of some common Xenons and a standard halogen for comparison purposes.

4300k D2S Philips = 3200 lumens
4300k D2R Philips = 2800 lumens
4800k D4S/R Osram = 3800 lumens – Best performing globe on market
5800k D4S/R Osram = 3300 lumens
7000k D2S Chinese = 1790 lumens
7000k D2R Chinese = 1390 lumens
8000k D2S Chinese = 1180 lumens
8000k D2R Chinese = 780 lumens

Standard OEM halogen 55W H7 = 1500 lumens

Just because this hid conversion appears to put out more light doesn’t mean that it does, the scatter makes you think there is more light and you loose depth perception and night vision the higher the colour temperature of the globe.

Under 4500K you get more yellow, between 4500K and 6500K you get more white and over 6500K you get more blue.

No OEM globe is 8000K and generally OEM is 4300K to 4800K because this gives out the most light. And there are no 10000+K globes either, these are globes that are ~8000K with a coating over the globe that further reduces the light output.


(photo from Bay Area HID Specialists)

Problem 3. Quality of the components

And how good are these “german designed and chinese made” kits? The decent Osram/Philips globes sell for around $200+ each online. The cheap chinese made kits comes with a pair of globes, ballasts and installation kit for around $150 so quality has to suffer, components to put together a decent OEM kit will come to $2000 and this doesn’t include the cost of the projector lamp.

Other then poor quality, high failure rate and poor performance the cheap ballasts can catch fire, your insurance may not pay out when your car burns to the ground or your wiring loom gets melted. Example 1,  Example 2.

To summerise, the higher the kelvin (temperature) the less light output you get (lumens) so stick around 4300K, if you must go for a retrofit get a projector light housing (oem where possible) and buy a good quality kit with brand name globes and avoid fitting Xenons to reflector lamps.

A few videos on why retrofitting Xenons should be avoided.

Video 1 Video 2

Daniel Stern is one of the worlds foremost experts on automotive lighting and has written an excellent article.

Tests by the DOT and CalCoast Labs on Halogen headlights fitted with Xenon’s.

Test 1 Test 2 Test 3

Nearly every country in the world has banned retrofitting Xenons.


Banned in Europe Banned in Hong Kong Banned in New Zealand

11 comments to Retrofitting Xenons (HID) Lighting to reflector housings

  • Lorenzo

    Has anyone installed in their mk6 the gti bi xenon kit, like 5k1 941 753 b (euro, right version headlight)?
    Do you think it’s going to be hard to install it? My dealer says that there should be some problems making the lights work with the can bus or something like this..

    • weil

      Hi Lorenzo, have you installed your HID on your mk6?
      i bought the hid kit (h7), bulb holder but don’t know how to do it?
      Have you done yours yet? If yes, have you done it yourself or get someone to do it?

  • Fantastic article. I’ve favorited this website so I can follow your follow-ups. Thanks for taking the energy to share this.

  • […] (and the wombat is moving at 8kph) lighting up the front of the car will do absolutely nothing. Retrofitting Xenons (HID) Lighting to reflector housings "With much of the light being scattered the performance of Xenon’s is generally nowhere […]

  • […] find specifically which bulb was in the GTI, although I did find the specs for some of the bulbs here Previously owned a MY08 Oettinger/APR Golf MKV GTI (R.I.P.) Currently own a MY08 Polo GTI with […]

  • Jason

    I have one of these kits in my high beams only in my mk4 GTI, and they DO throw the light far down the road, and it lights up EVERYTHING. I also have a “bi-xenon” retrofit in my gf’s mk4 Jetta, and it does exactly what this article says – blinds people and doesn’t light up anything except right in front of the car. My recommendation: definitely do it if you have separate high beams (going to test this on my mk6 golf in the future) and definitely DON’T do it if you have a single bulb for highs and lows.

  • […] would be easy and viable?! Easy yes, but illegal and dangerous to go down the aftermarket path. Retrofitting Xenons (HID) Lighting to reflector housings Fitting the OEM units is the only way to do this safely but the cost goes up and so does the […]

  • Boon

    I ordered my 2010 GTI with Bi-Xenon “cornering” headlights & they are great! Except…1 problem: they can’t be turned off during day time. I can turn the headlight knob to “Off” or “Auto”, these lights can’t be switched orr. For many weeks, my family & friends kept telling me to turn them off during day time… to prolong battery life… to save energy… But I can’t….

  • mani

    6000klevels are perfect for any vehicle cos 4000k still emits little yellow,wheres 8000k + emits blue which is very dangerous for the opposite vehicle…6000k pertfectly gives natural white with good balance…

  • […] Another site to peruse which advocates against the retrofit: Retrofitting Xenons (HID) Lighting to reflector housings | […]

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