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Re: Re: Spark Plugs
Hi Ruud, John, Fa Tom, all "pluggies",
Enter car buff ;o)).
Comments interspersed.
> Original Poster: "Jon Lagler" <rockcrawl-at-netzero-dot-net>
>
> > Original Poster: "DaxisWeb user" <""-at-mail.daxis.nl>
> > > > Original Poster: "Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com>
> > > > Tesla coil is designed to conduct massive amounts of current
>>>> and then quickly quench. They are both spark gaps, just as a
>>>> candle flame and the flame coming out of a flame thrower are
>>>> both flames.
> > > > Using a car spark plug as the spark gap in a Tesla coil will
>>>> work, but it does not work WELL. Neither will it survive too
>>>> long as a Tesla coil spark gap!
> > > >
> > > > Fr. Tom McGahee
Correct. You want a long "burn" time in a car. You canīt
"over burn" a A/F mix, but you certainly CAN keep a TC gap in
the "on" state too loong. Also, ignition timing is very critical (in an
internal combustion engine) because the A/F mix doesnīt ignite in
"zero" lengths time, which is why engines need advance from
TDC. To further complicate matters, this timing must be variable
to keep the engine happy under all runnning conditions. As to the
cooling, donīt forget that the engine head and block are massive
and provide cooling. In TC usage it might prove beneficial to use
"cold" plugs. Of course anything much above 1kVA will not run
well on a SPTG (spark plug type gap).
[Jon]
Snip. Btw: my scissors ran hot on this post ;o))
>>> What makes two copper pipes quench better than a spark plug?
Well two things really. One being a greater mass, so it de-ionizes
more rapidly and secondly the area is much greater so that the
plasma flame can travel along the whole Cu pipe, unlike a spark
plug, where the ionization and flame propagation occurs at a "pinīs"
point. Install a too hot spark plug on your car engine and it will start
to detonate, because the plug tip gets red hot and pre-ignition
occurs. Similar situation in TC usage.
[Ruud]
> > I can tell from experience that the car iginition coils I
>> played with (in my early days), that the primary coil mediocer
>> current was about 5A. So the consumed power was about:
>>12*5 = 60VA. Assuming Pp=Ps -> I = 60/40.000 > =1.5 mA!
[Jon]
> It would actually be more like:14*10 = 140VA. Assuming
> Pp=Ps-> I = 140/40000 = 3.5 mA.
>
> snip
[Ruud]
> >An 8 cylinder would
> > need a very impressive electrical generator, check it out: 8 *
>>40.000 * 1 = 320 kW! Mama heeeelp, the chevy will start but
>> not drive!!!
[Jon]
> Correct, except only one plug fires at a time so it would only be
> 40kW. Obviously there isn't a 40kW alternator in my car. I used
> the specs from an aftermarket high performance ignition coil.
>They claim "secondary voltage is over 43000 volts and the
> secondary current output is nearly two full amps.".
> Unless I'm missing something, this must be BS!
Ruud, Jon,
Jon is correct on the fact that the plugs only fire one at a time, BUT
it should be said that these values (V&A) are static values. Your
ignition voltage drops off quite a bit as soon as you start revving your
engine into higher rpms, which is one reason why the voltage *seems*
so high. Secondly, the amps (two in Jonīs case) are correct, BUT
there is the (not to be ignored) fact that this is of low duration.
These high current values are usually derived by a capacitor
discharge mechanism. A cap is charged to 300-400V and dumped
into the coil via a SCR. As power throughput is dependant on time
and the time duration is short, the actual average power isnīt very
high. The 5A primary current that you [Ruud] measure is an
average current, but not the peak current. The primary resistance of
an ignition coil is very low (typically <= 1 ohm). So as you (all) can
see, a typical *simple* car ignition system isnīt that simple at all.
Like quite a few things, when you *really* start looking at them.
Donīt forget that "simple" TC you are running (building) can easily
have a peak power of several tens of kW (even hundreds), yet it
is powered by wall power ;o))
[Ruud]
> > The dimensions of a spark plug are not dominated by the
>> sparks, but by the engine heath! Under all conditions the plug
>> must close the cylinder. With a temperature difference of
>> about 400-500 degrees Celcius between a cold engine and
>> one which is running top speed this is a hell of a job. A
>>spark plug is also not designed to get rid of the heath and
>> theoratical it will not be easy to quence hot air.
Well yes and no ;o) The engine is very sensitive to what kind
of plug you are using (be they hot or cold) and this depends on
a number of factors like cr, ambient temp, engine usage,
driving habits, etc, etc, etc. A full list would blow the bandwidth
of this list (and probably Terryīs patience ;o)). However [Jon],
you also shouldnīt forget that in an engine the spark plug is
actually cooled(!) by the detonation front of the igniting A/F mix.
Not to mention the fresh charge of A/F being introduced once
every four cycles.
> Well, the fact is, no mater what the numbers (and 'experts')
> say, my spark plug gap works very well for the little time
>and money spent.
Great to hear that it works. However Ruud and Fa. Tom didnīt
say it would NOT work, rather more like not suuuper good. I
would suggest you try a pipe gap and make true comparison
for yourself (and post the results), esp. when you start increasing
the input power. The broad knowledge on this list, pared with
the fact that coilers and coils have been around for roughly 100
years, makes it hard to discover something new (like the MMC
;o}). This List jumps the gap and presents every one on it with
infos and discoveries, making it quite possible for a "non" expert
coiler to get into long sparks rather quickly, which can (and should)
be seen in a positive (you get there more quickly) and negative
(increased risk to a beginner and you learn LESS) manner.
Best to learn by doing ;o)
Coiler greets from Germany,
Reinhard