Definition of HID  
High Intensity Discharge (HID) lighting is light from a plasma discharge rather than a filament.  The system involves a ballast to start the light and certain gasses to create the light.  Overall the system uses less energy than conventional halogen lighting, while producing 3x more light.  

How HID lights work  
High Intensity Discharge Lights do not have a filament.  Instead light is created from an electrical discharge between two electrodes in a micro-environment of xenon gas and metal halide salts.  The light is emitted by an electrically energized gas – a plasma discharge – formed and sustained between the two electrodes.  

The distinctive blue-white light of HID lamps stimulates the reflective paints in road markers and signs creating a safer driving environment.  Additionally, the increased light output is designed to illuminate a wider area in front of the vehicle, improving visibility and safety, without disturbing the vision of oncoming drivers

Why HID?  
HID lamps have over three times the lumens per watt of traditional halogen light sources and are more efficient at converting electrical energy into light. They produce at least 70% more light than traditional lamps, and use less power while producing less heat.

	Halogen bulb	HID lamp
		White	Blue White	Blue	Purple
Color temp.(K)	3,200 K	6,000 K	7,000 K	8,000 K	4,000 K
Luminance(lm)	1500 Lm	3,200 Lm	3,000 Lm	2,800 Lm	3,000 Lm
Life(hrs)	400 hrs	2,000 hrs	2,000 hrs	2,000 hrs	2,000 hrs
Wattage	55W-75W	35 W	35 W	35 W	35 W
Visual light	Yellow	White	Blue White	Blue	Pink Purple

The safety drivers deserve.  
Every night, drivers depend on their lights for safety.  With a more intense, whiter light than halogen, HIDs deliver three times the output, improved peripheral vision, and enhanced down-road visibility.

Some auto experts cite the almost complete darkness on isolated highways as a reason for why HID lighting is becoming popular. HID lights promote safety by providing a better overall view of the roadway and the ability to see upcoming objects quickly and more clearly. For example, road signs and objects on the road are easier to see when illuminated by HID headlights.  

Installation
Installation is a direct plug-in to the existing bulb wiring; no additional wiring is necessary in most vehicles.

Porsche's HID system, called "Litronic," was first offered for the 993 Turbo to replace conventional halogen bulbs for the low beams.  The 996 Turbo received HIDs for both low and high beams.

Now, any Porsche's lighting can be upgraded to this modern standard!  
- Low beam bulbs can be replaced for HID low / halogen high, like the 993 Turbo, 996, 997, etc.
- High beams can be upgraded on Litronic-equipped cars to get HID low + high, like the 997 Turbo
- Dual beam H4s and 9004s can be upgraded to a combination low+high HID

Model	Low Beam / High Beam	Fog	Driving
911, USA-spec thru 1986	sealed beam 40/45W *	H3
911, USA-spec 1987-89	9004	H3
911, RoW thru 1989	H4	H3
Includes 911 Turbos
964, USA-spec 1989-94	9004	H3
964, RoW 1989-94	H4	H3
Includes 911 Turbos
993, all, without Litronic	H1 / H1	H3
993, all, with Litronic	Osram or Philips / H1	H3
996, all, 1999-01, without Litronic	H7 / H7	H7
996, all, 1999-01, with Litronic	Osram or Philips / H7	H7
996, all, 2002-05, without Litronic	H7 / H9	H3
996, all, 2002-05, with Litronic	Philips / H11	H3
Includes GT3
996 Turbo, all	dual Litronic standard	H8
997, all, 2005-, without Litronic	H7 / H9	H8
997, all, 2005-, with Litronic	Philips / H11	H8
997 Turbo, all	dual Litronic standard
986, all thru 2001, without Litronic	H1 / H1	H3
986, all thru 2001, with Litronic	Osram or Philips / H1	H3
987, without Litronic	H7 / H9
987, with Litronic	Philips / H11
Includes Cayman
955 with I8BR (halogen)	H7 / H7	H11	H7
955 with I8BC (Litronic)
928, USA-spec thru 1986	sealed beam 40/45W *	H3
928, USA-spec 1987-89	9004	H3
928, RoW thru 1995	H4	H3	H3
944, USA-spec	sealed beam 40/45W *	H3
944, RoW thru 1991	H4 55W/60W	H3	H3
968, all	H4 55W/60W	H3	H1