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Spark Polarity & Twin Tower "waste spark" coil

 
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Pantera EFI



Joined: 12 Feb 2005
Posts: 1718
Location: So. California

PostPosted: Tue May 29, 2012 9:32 am    Post subject: Spark Polarity & Twin Tower "waste spark" coil Reply with quote

"Twin Post (waste spark coils) are DEAD for the high BMEP engine."

Sure, the low BMEP and medium BMEP engine will operate correctly with a "twin tower" waste spark coil.

REASON : A Sparkplug will fire much more easily from center electrode to outside ground.

Opinions, comments requested (invited)

Cases : GDI, Alt fuels, Fuel BSFC, Ultra Lean Burn, etc.

Lance
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Turboivo



Joined: 09 Mar 2006
Posts: 751
Location: Bulgaria

PostPosted: Tue May 29, 2012 1:13 pm    Post subject: Reply with quote

A theory says that electrons are more easily emitted from the hotter electrode i.e the centre one. That's what I know.
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buzzinhalfdozen



Joined: 30 Mar 2006
Posts: 93

PostPosted: Thu May 31, 2012 7:36 am    Post subject: Reply with quote

Though I work on this type system most every day, and it's operation has been explained to me at the training center on several occasions, it seems to be filled with contradictions. Many times it's been said that electricity is "lazy" it takes the path of least resistance. that statement being correct would seem to go directly against the "wasted" spark theory saying since there is no real resistance (cylinder pressure) very little of the spark energy is used on the "exhausting" cylinder. One would think that IF electricity in fact takes the path of least resistance it would expell MOST of it's energy to the exhausting cylinder. Perhaps there's a better explanation of the operation of this system that is unknown to me.
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RootesRacer



Joined: 04 Apr 2005
Posts: 485
Location: Arvada, Colorado

PostPosted: Thu May 31, 2012 8:38 am    Post subject: Reply with quote

Kirchoff's laws will tell you that in a network of parallel resistors, the bulk of the current will go to the lower of the two resistances.

Current does take the path of low resistance, but ignition systems power loads are not actually resistors. A better analogy for spark pugs would be high voltage zener diodes (the impedance drops toward zero ohms at the breakdown voltage).
A waste spark coil is a differential coil whose secondary "floats" and whose loads are the sum of secondary wires, and the two spark plugs.

Spark plugs are not resistors because when the secondary voltage ionizes the gap, the current begins to flow and the gap voltage will drop to the ionization potential for that fluid at that pressure.

The ionization potential increases with pressure so the ionization potential for the cylinder about to fire will be rather high, whereas the ionization potential for the "waste" cylinder is low.

The initial ionization potential for the non waste cylinder if often in the 10s of kvolts, whereas the ionization potential for the waste cylinder is hundreds of volts.

Since both the waste and non waste spark plugs are in series and see the same current, application of ohms law will easily show that the dissipated power on the non waste spark side is orders of magnitude greater than on the waste spark side.
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buzzinhalfdozen



Joined: 30 Mar 2006
Posts: 93

PostPosted: Thu May 31, 2012 12:00 pm    Post subject: Reply with quote

So it's the presence of pressure, not the absence of it that dictates where the most energy is being used? And by pressure we're simply stating there are more molecules in the same area for the energy to use? This makes more sense than the way it's been previously explained to me. With a somewhat limited education it's some times difficult to wrap my head around what's actually happening with this system.
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