HID lamps need about 200v to start up but will happily run on 12v - a bit like
fluorescent that needs a starter capacitor - however the light generated can be
likened to a welding arc which is exactly what it is and almost the same as the
old film lights that  generated UV to such an intensity that many old movie
stars went blind and got 2nd degree burns through UV radiation (sunburn).  

Search lights used in WW2 were also arc lamps so the actual technology isn't new
it just been developed for use in smaller places.  I also think the actual
wattage rating of HID lights are only 35W but the light output is brilliant
white (blue tinge) and equivalent to around 100W of incandescent.  Do to the
immense light output and the possibility of dazzle to oncoming drivers they must
in nearly every country they are allowed cars have to have self leveling systems
for the lights.

On cars with 4 head lights those that one would think are main beam are only
used to "flash" as it isn't advisable to keep turning the HID units on and off
and they also take about 2 seconds to come on to full brilliance and to self
level.

What's the difference in Projector lamps and HID lamps? I thought they were
the same ...

I've no idea. OEM include self levelling which may or may not be required
by local regs.

What's it cost to replace the standard headlamp (H4 or H7 <whichever>) lamp
with the HID?

Aftermarket HID kits work very well with BMW projector headlights - I've
tried them. And cost more like $150. Of course they may not conform to
local regs.

I'm with Dave on this one. LED lights as OEM equipment are very nice, but as
aftermarket stuff, they suck.

AS A MATTER OF RECORD
The headlamps are already halogen. There is no option for halogen, except
there are better bulbs that put the light spectrum in a different place.
There are High Intensity discharge light kits that you can buy, but at close
to $1200, it seems to me that the cost outweighs any benefit. You can get as
good as there is with a pair of $60 SilverStar bulbs.

In article
<72abbcaf-f30d-4a53-9860-75c856ac1923@8g2000hse.googlegroups.com>,

The lights on new cars are specially designed for LEDs. These so called
replacement LEDs for cars your age simply don't work as well as tungsten.
Try and find one which is 'E' marked as an allowable replacement.

Hello BMW owners,

I have 1999 323i, with regular bulb-lamps for its lights (headlights,
signal, tail lights).  I know there is an option to replace the
headlight with halogen -- but I was wondering, I see that there are
LED lights to replace regular bulbs for flash lights and some lamps
for home.  Is there any similar products for cars?  I don't think LED
is bright enough to use for headlights, but I think it can be used for
signal lights and taillights as new cars used these days.

The replacement LED lights I mentioned for home lights have the same
screw for the socket but just with LEDs.  So new LED lights can be
used without buying whole new one.  I was hoping to find similar
products for tail/signal lights for my car.

Does anyone know such products?

Thanks.