Bob Petruska

Are the factory Xenons white light or blue white?

€uroDan

I've had several occasions where I saw an oncoming car with xenon's when I thought "Whow, these are really blue". It wasn't till the car actually passed that I saw it was a new A4.

Don't know if Euro Audi HID's are different from US Audi HID's, though. This was in Europe.

DKelly3854

From what I have read, the color of light admitted by xenon lights changes (slightly) as the gas in the bulb ages. It turns more bluish as the bulbs become older.

€uroDan

Just don't expect them to turn to full blue. You slightly notice a difference, and see it clearly when one headlight has a new bulb, and the other one that's been used for a year.

Jason H

There are several different factors involved in the color perception of the lights, especially in the projector style lights that Audi uses.

The (stock) bulb itself is made by Osram and has a color "tempature" of about 4300° Kelvin. On this scale lower temps are closer to red, and higher temps are blue/purple (just like in a real fire, an orangish candle flame is cooler than a blue gas flame). This color temp is a bit cooler than that of some other OEM xenons, notibly BMW's. Seen from straight on a BMW with xenons would appear to be bluer than an Audi's. But of course ANY HID Xenon system is going to look blueish white next to a Halogen equiped car.

Now Some people have been unhappy with the fact that Audi xenons seem slightly more even white than the more bluish ones in other cars and have spent at least a couple hundred dollars to replace the perfectly good xenon bulbs in their cars with ones made by PIAA (Japanese) that are a color temp of 6000°K, which is definately into the blue/purple part of the spectrum. Below are a couple pics of two S4's. Both have E-code xenon housings. One has the PIAA bulbs the other is stock. The difference is pretty obvious huh?

<img src="http://pictureposter.audiworld.com/5479/sany0014.jpg">

<img src="http://pictureposter.audiworld.com/5479/sany0013.1.jpg">

I believe that Honda uses the PIAA bulbs on the S2000, so if you've seen one of those at night you'll have an idea of the color difference. Also these PIAA bulbs DO put out more lumens, so aside from the aesthetic difference there is more light output.

Finaly I wanted to mention that there are two factors that alter color perception. So far I have been describing the color as they appear to the driver or to someone looking head on to them at a low enough angle to be in the main part of the beam. Because the lens of the projector is convex the outer edge of the lens is at a larger angle to the beam of light, and the light becomes refracted (split like from a prism). Because of the way the bulb is in the housing the redish part of the spectrum is split to the bottom edge of the lens and the blue spectrum is split to the top edge. This is important, because coupled with the restrictor plate that cuts off the upper part of the beam, the light seen by most oncoming drivers will be that refracted light from above the beam cutoff. This light will look much bluer that the actual color of the beam. In fact because of the lens design my opinion is that from a far distance (more than 1/4 mile) Audi xenons look the most "blueish" of any manufacturer. With the 6000&deg;K bulbs you would still get this effect on top of the bluer beam. From a distance that would probably appear VIOLET like a blacklight!

Secondly, when the igniter/ballast first fires the system, the xenon gas burns hotter because of the initial charge, it then cools down to normal opperating temp. So for the first 30 seconds after you turn on the lights they will look bluer than normal as well.

Sorry for the length, but I wanted to explain this in detail, there has been some misunderstanding before. HTH. For more info just search for "6000k" in the archives, particularly the S4 forum (where I found the pics above).

Bob Petruska

What are you showing in the pictures? Are both cars equipped with Xenons and one has 4300, the other 6000k?

Jason H

And since you like the whiter ones, I think you would be happy with the factory ones.

motorwaffen

Impressive explanation!

dolphin_8E

i personally love the bluish haze of the xenons which is the sole reason i opted for them. i had the xenons on my 01.5 A4 and now on my 02 and love'em but wondered why they didn't look as "blue" as on Beemers... but you've broke it down perfectly. GREAT INFO! by the way, what model are those PIAA bulbs and where can a pick-up a set? how much do they go for?

Jason H

at the Tokyo Auto Show. You can't buy them in the US. I did find a site selling PHILLIPS 6000K bulbs D2S socket for $145/bulb free shipping. They have a lot of info about HID upgreades on their site:

<a href="http://www.autolamps-online.com/gasdischarge/index.htm"> Main HID page</a>

<a href="http://www.autolamps-online.com/gasdischarge/ultinon.htm"> 6000K page</a>

Also as of 1/23/02 there was a group buy on the S4 forum for these same bulbs for $250/pair from SPP. Search that forum to see if it's still on, or just contact <A href="http://www.supremepowerparts.com">SPP</a>