[Vwdiesel] Glowplug used for preheating swirlchambers at 6 volts. (

[Val Christian]

Hagar,

Data and conjecture.

Data first:  www.beru.com says that their glowplugs have the design
voltage stamped on the glowplug.  Looking at one I found in my 
"box of glow plugs", yes, indeed they have 11 or 11.3 on them.

Conjecture:  Since plugs tend to last about 60K miles, for me, and 
I start the car about every 5 miles, and 25% of the starts are cold
starts...  That's 12,000 starts, 3000 are cold.  3000 (45 sec) = 
135 Ksec + (9000 * (12 sec) or 108ksec) = 243 ksec = 4050 mins =
67.5 hrs.  Intuitively this sounds high, so worst case, 67.5 hrs (0.50) 
= 33.75 hrs.  You can now apply the reduction in life figures 
applied to high temp resistive heating elements.

Remember, that some resistive elements are non linear in life
expectancy.  This can be because of design limitations.  One
such limitation might be the heat sinking to the threaded base 
of the glowplug.  My guess is that if that were the case, it would
work in your favor.  

You could try a test sample of one, a new plug, and run it with a 
regulated supply (in lieu of a battery), at 6 V or 5.5 V if that works
for you, and watch the current over time.  As the element has 
localized depletion, you'll see a slight drop in current.  This is
akin to an incadescent lamp "yellowing" where the average filament
temperature drops with age, but some localized spots on the filament
are actually hotter, due to the necking of the filament material.
You can visually see this on filaments, as they age.

My guess is that in moderate cold (about 15F) you'll find that you 
will want to run the glowplugs for several hours (4 or more) and 
that you'll need a sheltered location for your engine.  It's like
preheating an aircraft engine in the hangar with a 60 or 75 watt
bulb in the engine cowling.  No wind, perhaps a blanket over the 
cowling, things get real toasty.  Out in the howling wind of a 
blizzard, at -5F, life is different.  Heck, the 700W block heater
on my tractor has problems in that environment.

Val







> 
> Val Christian tossed this at us  ----and with my  blockheater burned out
> and frost on the carrots.
> 
> I decided to test it out -----   lot of fun.      But takes a lot of =
> time to get the heat
> right.  I started with 5 volts   -----4 big   NIFE   NiCads.
> 
> Hagar.
> 
> PS :    So far   BOSCH has only  come forward with design voltage   (11 =
> Volts they say)
> 
> I am waiting for design life .    -----anyone have an Idea ?    500 =
> hours ?.
> 
> Cold start trick  for MIKE in   NB  lobsterland.
> _______________________________________________
> Vwdiesel mailing list
> Vwdiesel at vwfans.com
> http://www.audifans.com/mailman/listinfo/vwdiesel
>