Taken from Boxa.net..
So after a few threads, I decided to make this a go-to thread for information regarding anyone considering a HID upgrade.
What is a HID bulb.
A HID (High Intensity Discharge) bulb has become increasingly popular with modern cars due to their lifetime and power. The bulb itself has no filament, instead it contains two diodes with a capsule full of Xenon gas in the centre. The diodes ignite the xenon gas instantly, and light is emitted.
There's four main aspects to a HID kit:
Bulb - The bulb itself and its fitment. Bulbs come in normal fitments (H1, H7, etc) and can fit in most applications. The bulb also determines the colour.
Ballast - The ballast is the device that ignites the bulb, and supplies its power.
Wattage - This is down to the ballast, not the bulb. There are two common wattages available for ballasts; 35w and 55w. There's no issue with using either. I've ran both and found 55w to match OEM installed kits on other cars very well. The 35w kits tend to be slightly cheaper, but their output is still far better than that of a halogen bulb.
Canbus - This is designed for cars that detect bulb failures. A canbus HID kit is required for the 986 Boxster. Although the Boxster doesn't detect a failed bulb, a non-canbus kit plays havoc with the cars electrics, triggering warning lights and other anomalies.
Legalities of a HID kit.
In short, they're legal to use but with a few provisos. Garage have a tendency to think "They need self levelling and washers on the lamps to be legal", and they're right, for OEM installations. But the MOT guidelines from VOSA state that they need to work "where fitted". They are not required for an aftermarket installation, they just need to work where fitted. This was confirmed by VOSA when I requested information on it.
There's two things that will fail an MOT with a HID kit. The two things are the colour, and the beam pattern. Both explained below.
Colour.
The bulb is responsible for the colour (temperature) of the light. Measured in kelvin, the lower the number, the more towards the warm side of the spectrum the light goes. The higher, the colder. The most common application is 5000k, as this is considered a good choice in terms of light output.
Here is what each temperature will look like (this is amended by myself to better represent the colours):
"But modern lights are blue, right?"
No. It's an extremely common misinterpretation with what colour to choose, as most people think "Modern lights look blue, so I need to get ice blue, so therefore I need to get 6000k". It's nonsense. There are no OEM applications that use 6000k bulbs. The closest is 5500k, but that temperature isn't available commonly as aftermarket. The reason why modern car lights look white/blue when you look at them is due to the colours splitting in the lens I'll explain below:
That's what a beam pattern looks like from a projector lens, fitted with a 5000k HID bulb. Notice that blue line? This is due to the lens refracting the light and the colours splitting, showing a very thin spectrum. This can sometimes be red, violet, blue, etc. That's what you're looking at when you look at on coming traffic. Look at the light colour itself - see how it's a normal white/warm light?
If you have a very blue light, this can fail an MOT and can also get you pulled. It's not worth it.
Which also leads us onto...
Beam pattern.
Unfortunately, if you're considering a HID upgrade for a 986 Boxster (non-litronic), my initial recommendation would be not to. There's two different types of headlamps, reflectors and projectors. Reflectors (standard 986 Boxster) use the mirrored shape of the headlamp to produce the beam pattern, where as a projector lens (litronics and all 987/997 onward lamps) use the projector and a physical shield inside the lens to create the beam pattern.
A HID (or LED) bulb is a different shape to a halogen bulb. In a projector, it doesn't matter as the physical shield blocks light from scattering upwards, so you get great results with any brighter bulb. Using a HID bulb in a reflector will distort and blur the beam pattern because of its different shape, and it'll cause glare upwards, blinding other drivers.
This shows exactly what I'm on about:
The top photo is what you will have if you put HID's into your standard Boxster 986 headlight, and it's not good.
So can I use HID's in my Boxster?
If you have a 987 boxster, you're fine, as these have projectors as standard. Go ahead and buy a H7 Canbus HID kit.
If you have a 986 boxster, It's not recommended you use HID lights in a standard headlight.
I have a 986 and want HID's. What can I do?
If you have a 986 boxster, it's not impossible, but it's a little more tricky.
You have four options:
1. Buy pre-owned OEM litronic headlights. These will be plug and play to get the headlight working, but the auto-levelling won't work. They can be very expensive too, at around £1,000 for pre-owned sets. No need to install HID's in these as they're built in.
2. Buy aftermarket headlights. Some have projector lenses in them, but these can be in excess of £1,000. You could buy pre-owned litronics for that. You'll then be able to use a HID kit. Be sure to read reviews though before purchasing.
3. Install a HID kit using reflector-friendly bulbs. If you're desperate, you can use HID's in the 986's reflector headlamps but only with special bulbs. The 986 uses H7 fitment bulbs, so buy a HID kit and use H7R bulbs (you can buy the bulbs separately, most HID kits have the same connectors). The 'R' in the name stands for 'reflector', and it's a HID bulb designed (loosely put) for reflector lamps, as the bulb has a painted shield on it to stop light going upwards. They're good, I ran them for a while and they're not too bad at all, the design of the 986 reflector surprisingly doesn't produce much glare with a H7R bulb. The only thing you'll suffer with is any sort of clean beam pattern, as it'll be blurry. But please don't even consider running normal H7 HID bulbs - only use H7R bulbs, and run 5000k or lower due to the issue of potential glare. Your beam pattern will fail the MOT, so change them before the test day.
4. Install projector lenses. You can buy aftermarket projector lenses to install in your headlight, like I have:
See the projector lenses? Those. Then you'll have an incredible light output. The lenses only cost £18, and the HID kit costs around £40. The biggest price you'll pay is the labour of splitting your headlights and installing these, as there's a lot of fabrication needed as they're not plug and play in any way. I won't cover how to do that here, as 986forum.com has a few guides. It doesn't take long to do (I did both headlights in one evening), and the results are absolutely incredible, but it's far from easy.
Extra information
Halogen alternatives. If you're not feeling brave enough to install projectors in your headlights (and I can't blame you having done it), there's two ways you can go with a halogen bulb. The first is a HID look-alike bulb, like an MTEC SuperWhite or CosmoBlue bulb. These are coated with a blue tint, which cancels out the warm halogen light, creating a white light. The only issue is that due to the nature of the bulb having a cover on it, they're not as bright. The other route is to get a far brighter halogen bulb, like an Osram NightBreaker. They're normal colour though.
Ballast install locations. Something to keep in mind if you're fitting HID's. The ballasts produce quite a bit of heat. I've seen people install them inside the lamp assembly but they're far too hot for this. What you'll need to do is drill a hole in the rear detachable cover, and mount the ballast to the outside of the cover. Then feed the wires into the lamp through the cover.
Cheap kits. Two places to avoid - Ebay, and HIDs-Direct. Ebay sells kits for less than £20, and these will bring you endless problems of mis-matching bulb colours and flickering bulbs/ballasts. HIDs-Direct are also dreadful for build quality. Their kits don't last at all, and I've had to replace a ballast 4 times in the space of a few months. I sent a few straight back too as they had clearly been thrown around or used, covered in dents, marks and dirt. They're horrendous. Scour the net and look at some decent kits. HIDS4U seem to be excellent.
So there we are, hopefully I've cleaned things up!