<E30> throttle body preheater caution, Blue vs. Violet lights

["Lin, Gary" <Gary.Lin@xxxxxxxx>]

Just got around to writing up about my blown TB preheater gasket; caused me
to have to fill up the coolant tank every 10 miles coming back from M Day;
at least I made it home without an overhaul scare.  It's a stupid little
$1.50 cork part; sits between the TB and the coolant chamber where two 1/2"
coolant hoses come in from below off the block.  If your engine is over 75K,
look it over.  Mod tip:  climates south of Canada can probably do without it
and still pass emissions according to noted national and local BMW techs.
Just go to Home Depot and buy a connector sleeve to clamp the two hoses
together and bypass the TB; wallah, cooler intake.

For M20's, release system pressure.  You'll need to remove the airbox, AFM,
and loosen the 4 nuts bolting the TB to the manifold in order to get the
T-20 torx driver (socket will not fit between the runners) onto the 3 screws
holding the preheater onto the TB.  You don't need to fully remove the TB.
Tap torx lightly with a hammer to break loose before unscrewing in order not
to snap off a corroded screw.  Replace gasket.
- -----

There are several issues in dealing with blue lamps.  First, look at the
light spectrum, long to short wavelength: ROY G. BIV- InfraRed, Red Orange
Yellow Green Blue Indigo Violet, UltraViolet.  High Intensity gas Discharge
lamps are near the Violet end, not middle Blue.  HIGH intensity blue
(daylight) scatters more.  Notice how much sharper violet toned HID lights
are than yellow/blue incandescents.  New tech for the future is UV enhanced
lighting, like the 70's blacklight, because it causes colors to fluorese or
glow, much improving night visibility.

Blue or Green LOW intensity lighting for instruments could be desireable; I
personally find blue-green instruments easier to read than orange ones
because your pupils don't have to dialate as much after being blinded by
oncoming misaimed headlights and rogue driving/SUV lights.

Gary Lin    National Capital Ch.
'88 325is lachssilber   Conforti, Supersprint, ///M susp., Ints., Kumhos

Brad Purvis wrote <snip>:
> Second is that blue lighting puts less strain on your eyes and the eye is
> most sensitive to blue-green light (meaning less is needed).  The real
> issue here is what is luminated using either white or blue light.  If the
> two lights are of equal luminance, the blue light will always look
> brighter to the human.  This is brightness perception which uses all the
> color channels, both chromatic and achromatic.  Luminance is a photometric
> measure which is measuring the number photons striking an object per unit
> area.  So to cut to the chase the same two lights, one which is perceived
> as white while the other which is perceived as blue, with equal luminance;
> the blue light will always be perceived as brighter.
> 
> Brightness is a human perceptual measure, luminance is photometric
> measure.  The lighting companies know this and do not use blue because
> most people are used to white hues.  If you want a good reference to this
> subject, try "Color In Electronic Displays" edited by Helino Widdle and
> David Post.

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