Re: Xenon HID retrofits: an optical engineer's view


"JB" <JB@xxxxxxxxxx> wrote in message news:4e522dF1clbmaU1@xxxxxxxxxxxxxxxxx

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"JB" <JB@xxxxxxxxxxxx> wrote in message
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I modified a pair of spare headlight units for my SO's BMW E36 over
the
last week or two. Osram ballasts, Philips D2S lamps and original
Bosch
reflectors with special cutoff 'masks'. The difference is simply
*astounding*. I knew they would be an improvement, but Jesus do they
do
the business. Not an easy DIY conversion unless you have access to
the
kit I've got at work in the lighting lab, but still not too
demanding.
For a comparison, I tried a pair of these Chinese
"Sooper-Dooper-10000Kelvin-Burn yer Eyeballs Out & fry yer Ballasts"
H1
retrofits which my friend had bought from Ebay for about £240. These
so-called retrofits are a cheap copy of the Philips D2S arc-tube
cemented into an H1 halogen base with heavily insulated flying leads
(25kV ignition voltage. V.Nasty). Once fitted into standard E36
headlamp, I photometered the original 55W H1, this Chinese one, and
my
conversion with a properly focussed Philips D2S lamp. Considering the
'claimed' 4x lumen output of the Chinese lamps, they actually
produced
only a real 13.8% improvement in lamp lumens reaching the road
surface
over the original Bosch H1 halogen units. The beam quality however
was
******* and certainly illegal.
Using correctly focussed genuine Philips lamps and new masks in the
same
reflectors, the improvement became 281%! Xenon HIDs do seriously
*rock*.
I seem to have also gained a spare ballast and lamp too which will
now
be going into my Trike's Cibie 'Z-beam' low beam unit :>).


So basically what you're saying is run 100W bulbs and don't bother
pissing about unless you want to lay down serious cash?
Unfortubnately no. 100W lamps will kill the reflector coating in very
short order. The easiest way to improve the e32/e34/e36 low beam
ellipsoidals is to use Osram Silverstar lamps. Same wattage although
less
lamp life, but lots more luverly lumens. Not cheap, but well worth the
outlay.
The HID conversion was for me at least, an interesting (and fairly
cheap)
project. I got the £270 ballasts as 'evaluation samples' from the
manufacturer and the Philips D2S lamps from Ebay, for £25 a pair brand
new. The biggest pain was reworking the lampholders/mountings and the
the
new s/s masks.

Even the old fashioned Hellas on my Golf? Seem to be chrome plated steel
reflectors (MK2 Golf, round lamps)

You'll be ok with a chrome plating and high wattage lamps, but chrome
hasn't
been used for years. The plating process uses some nasty chemicals and the
waste is classed as toxic. Modern reflectors, even steel ones use vacuum
deposited aluminium reflector coating. This is quite soft, and susceptible
to 'heat blooming' (oxidation). Aluminium is a much better reflector
material optically than chrome too.

How modern's modern? 15 year old car...


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