<VV> Re: <> Re: main jet vs idle and spark plug miss

[burkhard at rochester.rr.com]

John -

I haven't tried Frank's test, but the concept of series gap spark plugs 
is fairly well known. By introducing the additional gap upstream of 
the "business" (in-cylinder) gap, you basically keep potential at the 
main gap low until the "moment to strike" is right, when it is hit with 
a lot of potential all at once, rather than more gradually. This helps 
avoid charge leakage to ground on the in-cylinder gap and subsequent 
loss of ignition energy. This is a pretty simplified explanation, but 
it's basically what has been going on. You can (or used to be able) to 
buy such add-on gizmos for use in engines that tend to foul plugs.

Jim Burkhard

----- Original Message -----
From: John Dozsa <jdozsa at carr.org>
Date: Monday, November 21, 2005 10:23 am
Subject: Re: <VV> Re: main jet vs idle and spark plug miss

> Thanks for the reply.  I've seen Jim Burkhard's excellent post 
> which I
> fully understand.  I'm trying to put some theory behind the additional
> spark gap making a improvement.  We know that increasing the spark 
> pluggap with and improved higher voltage ignition system will improve
> things.  Since the plug gap is larger the ionization voltage is 
> higher. 
> The spark energy for combustion is greater because the voltage at the
> instant of spark the voltage is higher.  That along with HEL, CD, etc.
> allows greater current flow and a hotter spark.  BUT, the additional
> spark gap test is doing none of that.  It is just making an additional
> spark gap. An external one that has only air to ionize and the still
> unchanged plug gap with the complex air fuel mixture to ionize. 
> Assuming the ignition system has enough high voltage to break down 
> bothgaps the cylinder will fire.  For significant current to flow 
> both gaps
> must ionize.  Which one ionizes first I don't know but some delay must
> be introduced.  Could it be that the additional delay caused by second
> spark gap allows additional time for the cylinder lean conditions to
> improve and now fire the plug?  
> 
> I've added Jim to the distribution.
> 
> John
> 
> > Frank DuVal wrote:
> > 
> > John Dozsa wrote:
> > 
> > > Hello Frank,
> > >
> > > I've been following Padgett's trouble shooting with considerable
> > > interest.  I'm intrigued by one of the suggested troubleshoot
> > > techniques.  That is:
> > >
> > > 1. Create an external spark gap in a particular plug wire by 
> pulling> > the
> > > wire partially out.
> > > 2. The gap needs to be small enough to still fire that plug.
> > > 3. Observe the resultant cylinder firing.
> > > 4. If the engine runs better momentarily, it indicates a lean
> > > mixture at
> > > that cylinder.
> > >
> > > Do I understand it correctly?
> > >
> > > While I understand gaping plugs wider increases the voltage 
> when the
> > > plug fires, which compensates for or masks a lean fuel 
> mixture, I do
> > > not
> > > understand how an additional series spark gap can create the same
> > > condition.  Am I missing something?
> > >
> > > Please explain.
> > >
> > > John Dozsa
> > > jdozsa at carr.org
> > >
> > >
> > 
> > On step 4, it is not momentarily, it can run well as long as the 
> spark> gap is in place. But, a lean cylinder is only one condition 
> that will
> > be improved with a hotter spark. It also can fire a fouled plug, and
> > maybe other marginal ignition parts. Swapping out the parts 
> leaves the
> > lean condition as a cause of hot spark cure.
> > 
> > The first time I heard of the spark gap test I thought it was bogus.
> > But, it really works on point style ignition. The theory should also
> > work on electronic ignition, but the voltages are already 
> higher, so
> > probability of damage to ignition components or personal injury is
> > much greater. An HEI system nornally fires through .060" gap and 
> hurts> when it finds you. With a .250" gap or greater, it will 
> find you with
> > shocking resulys. A good working  points ignition system can 
> fire a
> > 1/2" gap with a blue spark. The color and length of spark is a good
> > indicator of voltage available. This would be a typical old school
> > ignition test at cranking speed for no- start troubleshooting.  Jim
> > Burkhard had a good explanation in a later VV message. The coil 
> is the
> > generator of spark voltage. The windings turn ratio determines the
> > operating voltage. But the voltage is generated by the collapsing
> > magnetic field exciting electrons in the windings. So, the primary
> > winding forms a magnetic field with the points closed. When the 
> points> open, the collapsing magnetic field sweeps by the 
> windings, like a
> > moving armature sweeps by field winding magnetic field in a 
> generator,> and this voltage at the tower terminal will rise until 
> it finds a
> > return path to ground, the other terminal of the high voltage coil
> > winding. The saturation level of the coil limits the amount of 
> energy> available to raise the voltage.  When the spark gap fires 
> the energy
> > is diisapated, and the voltage goes away. The size of the spark gap
> > is relative to the ionization voltage of air.  The larger the gap,
> > the  higher the voltage. The more small  gaps in series, the  larger
> > the gap appears to the coil output, as the voltage has to ionize all
> > the gaps at the same time to fire.
> > 
> > >
> > >
> > >
> > >> Frank DuVal corvairduval at cox.net
> > >> Sun Nov 20 11:43:37 EST 2005
> > >>
> > >>
> > >> Dan Timberlake writes:
> > >> "And ignition components subjected to multiple full power hi-pot
> > >> tests with plug lead yank-offs.  I provide Genuine grounding,
> > >> Especially on fragile vintage European electronic ignitions, but
> > >> even on points ignitions,"
> > >>
> > >> I would not hi-pot test an electronic ignition system, but have
> > >> removed spark plug leads from many a distributor on points 
> systems> >> to troubleshoot. The old  adage works here: "if it 
> fails, it was
> > >> bad anyway".  Pulling the plug wire out of a running distributor
> > >> should be done with knowledge of where the spark will jump to and
> > >> how it will hurt you! But, it provides another piece of the
> > >> troubleshooting puzzle: If a cylinder starts running better when
> > >> the plug wire is pulled out 1/8" to 1/4", just to where the spark
> > >> is heard clearly, then the spark plug is firing with  higher
> > >> voltage. Hence the hi-pot terminology of running without  the 
> plug> >> lead connected. If higher voltage make the cylinder fire, 
> but not
> > >> fire with normal voltage then you could be firing a leaner 
> mixture> >> and therefore a fuel system lean condition due to carb 
> problems or
> > >> vacuum leaks. You should swap out the wire and plug to eliminate
> > >> them as suspects as high resistance wire may also need higher
> > >> voltage, or a fo
> > >> uled
> > >>
> > >>
> > >  plug. Many 2 stroke engines that fouled out can be run with the
> > > plug lead pulled out slightly. Also, if you are old enough you can
> > > remember the snake oil salesmen with the gadget that they inserted
> > > in series with the center tower on the distributor and coil lead.
> > > The engine was run with out the device and a tachometer showed a
> > > certain RPM. They then inserted the device and the tachometer 
> showed> > more RPM. Hucksters I tell you. It was nothing more than 
> a spark gap
> > > to provide a higher voltage spark at idle. Maybe they leaned 
> out the
> > > mixture to get such a change for their demo. I saw it demonstrated
> > > on a Pontiac straight 8 flathead back about 1960. J.C. Whitney 
> also> > had them for sale....
> > >
> > >
> > >> I have also heard more cylinder compression needs more spark plug
> > >> voltage. Hence the better coils on the Spyders.
> > >>
> > >> So Padgett, does the #6 plug wire making the engine run 
> better for
> > >> a second occur when the plug lead is close enough to jump the
> > >> spark gap?
> > >>
> > >> Frank DuVal
> > >>
> > >>
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