the factory fog lamps on my Trans Am throw out less light than the park lamps. I think I've turned them on twice... in the fog. But because my car (used to have) has DRL's and automatic headlights I don't (didn't) have a lot of control over them...
I sit corrected. The HID lamps appear to be a popular option; most all of the '04-up Priuses I've seen recently seem to have them.
Is there any technical reason, like HID lamps not liking the cold, that this is so? Or is it some more mundane cost or styling reason.
Matt Roberds
HID lamps love cold weather :-) They run so hot that, unlike fluorescent lamps, their performance is not changed by normal ambient temperature changes. And, since automobile headlamps use xenon instead of Hg, they aren't even any harder to start when the temperature drops. (Due to the high pressure xenon they are hard to start all the time. )
Yep! Canada requires Daytime Running Lamps. The least-expensive way of implementing them, both from a build-cost and warranty-costs standpoint, is to put the high beams in series with each other, but this is of course applicable only to incandescent lamps. It doesn't work with Xenon. Toyota apparently felt that the increased incidence of early HID component failure within vehicle warranty period, in addition to higher warranty replacement rates for parking, sidemarker and taillamp bulbs (required to be energized with full-intensity-lowbeam DRLs, and there is no other kind based on HID headlamps) would drive up warranty costs excessively. Apparently they also felt that using the turn signal DRL system they use on some of their trucks was for some reason a nonstarter. *shrug*
So, all Canadian Prius buyers get 1972-tech headlamps.
DS
Bzzzt! Current-production automobile HID headlamps most certainly *do* use Hg. Hg-free automotive HIDs (D3S, D3R, D4S, D4R) have just been approved recently. They are not interchangeable, optically or electrically, with the existing D1S, D1R, D2S, D2R bulbs. DS
You are correct. I should not have said "instead." I should have said "in addition to the Hg." Since they use a high pressure of xenon to provide "instant light" they are always hard to start, about as hard as a conventional metal halide lamp during hot restart. Hence the high voltage starting circuits of their ballasts.
Normal HID lamps that do not have a fill of high pressure rare gas are relatively easy to start since both the Hg and the metal halides will condense when the lamp is "cold" and the arc tube pressure during starting will be controlled by the relatively low fill pressure of the rare gas used to enable starting. (As you know, this gas pressure is optimized for easy starting, not instant light.)
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