[Vwdiesel] glow plugs low voltage

[Roger Brown]

You could also do a simple ballast resistor to drop the voltage, about 0.4 ohms/100W wirewound resistor feeding the 4 plugs
would do the trick.  What to do with the "wasted" heat from the resistor?  How about use some JB Weld or other epoxy to glue it
to the oil pan or block to soak up the heat.  That would give you about 200W of power into the engine, 1/2 to the head, 1/2 to
the pan.  Put in a second battery (deep cycle) to power it and have that automatically recharged by the alternator.


> >Musings from the near north
> >
> >I set up a haywire test set on the bench tonight to try some things.
> >
> >Heavy duty batt charger
> >Metered Variac (variable transformer to adjust primary voltage)
> >Digital volt meter
> >DC ammeter
> >
> >2 different glow plugs, one Beru (made in Germany) straight tube with blunt
> >end,
> >The other, a Bosch with the tapered tube (made in France) part # are on the
> >plug, but I didn't bother reading that just yet (very tiny print vs. old
> >eyes, Need the illuminated magnifier)
> >
> >The following figures are not absolute, but practical. Perhaps later I will
> >do some more accurate measurements.
> >
> >Reasoning that extended time operation would likely be best done at a
> >voltage/current resulting in  just barely visible redness, adjusted the
> >variac to get a faint glow.
> >
> >3 to 4 amps, about 4 volts = 16 watts, 4 of them would be about 64 watts,
> >about  that of a 60 watt light bulb. Not much compared to the common block
> >heater.
> >
> >Typical frost plug block heater for VW is about 300 watts.
> >With a thoroughly cold soaked engine to -20C, a half hour of 300 watts will
> >bring the engine to a good starting temperature (start guaranteed).
> >
> >There was an interesting difference between the Beru and the Bosch.
> >
> >The Beru draws more current as the voltage is raised, more or less
> >linearly,
> >while the bosch, once the voltage gets to 6 or so, any increase in voltage
> >is met by a decrease in current, keeping the wattage more or less constant
> >above 6 or 7 volts. As I increase the voltage, the current goes up for a
> >moment, then drops back to slightly less than before. This is obviously the
> >ballast trick we have recently read about on the bosch web site.
> >
> >At this level, from 7 volts up, the color remains about the same, quite
> >bright. I really need to mount it in a large heat sink like a chunk of
> >engine head to do a fair assessment, as quite a bit of the heat goes out
> >through the threads into the head.
> >
> >Summary:
> >The 115 volt block heater is about 300 watts, and is very effective, Able
> >to
> >warm a COLD engine to easy starting temperature in about half an hour, and
> >if left on all night, the engine will be at summer temperature in the
> >morning.
> >
> >The glow plugs, in normal use,  produce slightly more than 100 watts each,
> >x4=400 watts
> >
> >Use of the glow plugs at lowered voltage (4 to 6 volts) as a head heater
> >would probably be practical, if used in conjunction with synth oil to
> >ensure
> >fast cranking.
> >
> >6 volts would probably be the max for the plugs, to avoid running them at a
> >temperature high enough to cause deterioration of the iconel sheath, or
> >internal resistive element
> >
> >The argument for 6 volts would probably be good for plugs mounted in a sink
> >like the head, to prevent overheating
> >
> >This would result in about 100 watts total for the head,  1/3rd that of the
> >block heater, and only heating the upper third of the engine (the head)
> >where it will do the most good
> >
> >Now the how?
> >
> >I opened a glow plug relay to ensure there is no connection of any kind
> >from
> >the glow plug rail back to the circuitry. There is not, as long as the
> >relay
> >is not operated.
> >
> >This would permit the use of a 6 volt,  20 amp transformer (120 watts) to
> >power the plugs with A/C.
> >These may be found by dumpster diving (a la Hagar), or ham radio flea
> >markets, but it occurs to me there are tons of 5 volt, 20 amp and up
> >computer power supplies lying around everywhere. I must have half a dozen.
> >Bonus, there's usually a 12 volt section , that if adjustable, could be set
> >to 13.6 volts for the most perfect regulated battery float charger you
> >could
> >ever ask for.  I would not suggest the power supply from a PC clone, as
> >they
> >are not usually adjustable, but supplies from larger computing equipment
> >that are a glut even at junkyards, would do the job.
> >
> >Now, what to do in the middle of a 40-acre parking lot.
> >
> >1. The large 6 volt battery on the glow plug rail for 3 or 4 hours, total
> >16-20 amps, needs to be about 100 ampere-hours, and in addition, needs to
> >be
> >a deep cycle, as an ordinary cranking battery will tolerate about 6 total
> >discharge, recharge cycles before it lies down and dies....permanently
> >2. There is a better way, a 12 volt, 120 ampere hour, deep cycle RV
> >battery,
> >with a 400 watt inverter to get 115 volts A/C, applied to the electric
> >block
> >heater for 1 hour max, will get you a toasty start, and you can recharge it
> >on the way home from your alternator. Because of entropy (water runs
> >downhill, but you have to push it back up, and sweat at the same time), You
> >need a battery that can maintain its terminal voltage above the inverter's
> >auto cut-off voltage, for the time required. This means you need battery
> >capacity about twice as much as the calculated draw of the block heater for
> >the required time. The fully charged RV battery will crank out the 28 amps
> >needed for well in excess of the hour you need.
> >
> >Furthermore since batteries cannot be forced to take a complete charge in a
> >short time at 13.6 volts (your alternator output, if you are lucky), you
> >will have to charge the battery at home all night at a few amps to bring it
> >up to full health for the next day.
> >But it can (and has ) been done.
> >
> >This is my choice until I can get my oil burning wintermiser heater
> >installed.
> >
> >Some of us must park many yards, or even miles, from the nearest electrical
> >outlet, (like my wilderness camp) and these tricks can help.
> >
> >And, of course, there is the Coleman stove, the pan full of briquettes, the
> >propane lance on the block, etc. All these have been done and work.


--
   Roger