Thread: HID FAQ
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#1: 09-10-2004, 01:10 PM
 Drift Monkey
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Location: Houston, TX
Car: Subaru Legacy 2.5GT 5MT
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Since there are so many HID questions (and requests for me to do one), I've decided to do a little FAQ. 8)

Q: What is HID lighting?
A: High Intesity Discharge lighting. HID lighting technology replaces the filament of the light bulb with a capsule of xenon gas. The light is emitted from an arc discharge between two closely spaced electrodes hermetically sealed inside a small quartz glass tubular envelope capsule. To operate, they require ballasts, which supply proper voltage and control current. The amount of light produced is greater than a standard halogen bulb, while consuming less power, and more closely approximating the color temperature of natural daylight.

Q: Do I need HIDs?
A: Many owners would argue no. The projector setup is supplies more than adequate lighting for all points and purposes. HID lighting does have it's advantages however. HID lights generally emit a greater amount of light per wattage and produce a purer, whiter light, closer to that of the sun. Halogens are yellowish in comparison. The bulbs also last longer than standard halogen bulbs and in some cases 3 to 5 times as long! Do remember that this comes at a cost as HID bulbs generally cost much more than standard halogen bulbs.

A low cost alternative many owners have tried (with success) is swtiching to Osram Silverstar H7 bulbs. Do not confuse these with the Sylvania Silverstars found in local autostores, as these do not have a blue tint to them. Blue tint, while emitting a whiter light, decreases total light output and usable parts of the usable light spectrum during incliment weather. The bulbs desired are as pictured and can be purchased through retailers such as , , and many other reputable online vendors, as they are not available in the US.

Osram Silverstars:

Image coutesy of

Q: What HID kits fit the Legacy?
A: A H7 kit is required. Make sure this kit includes D2S bulbs.

Q: What is the difference between D2S and D2R bulbs?
A: D2S bulbs are make for projector type housings while D2R bulbs are made for reflector housings. The Legacy utilizes a projector layout, so D2S bulbs are required for correct light output.

Q: What kelvin (K) temperature rating bulbs should I get?
A: Bulb temperatures range from 4100K - 6,000k+. Higher the temperature ratings indicate more blue/purple light output. Note that the 4100K bulbs are the whitest lights available and therefore produce the most usable light. 5000K bulbs produce a bluer tint, and 6000K+ produces a more blue/purple light output.


Note: 4300K is very similar.



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