spark enhancement device

jaguar

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#1
I don´t remember where but I have seen a device written about that was basically a high voltage diode leading to a capacitor (that had its other leg tied to ground)
SO I tried to duplicate the same but wasn´t sure about the voltage that the capacitor would have to endure. I used two 1Kv diodes in series and used six .01uf 1Kv capacitors in series.
Kicked it over and got zilch spark. nada.
Could be that the capacitance was too much or that the voltage is more than 6000 and was more than the caps could handle.
?So please tell me what the voltage is to gap .035

Continuing to experiment;
I played with just the diodes. One direction gave better results than the other. (diode band closer to the coil)
Also with the diodes I could get it to spark a greater gap than without diodes. But the spark looked the same with a normal spark gap.
 

motometal

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#2
The voltage is much higher than that...at least 20 kV and probably more like 30 - 40 kV.  I think you are right that in your first test, the potential was just shorting out across the plates of the capacitor.  The capacitor had less resistance than the plug.  It may have even welded a few of the plates together, creating a dead short.

Capacitors pass ac, but store dc.  But the diode wouldn't allow any ac to pass.  So (if the capacitor could handle the voltage), and assuming we are starting with a discharged capacitor, the capacitor would charge and cause a resultant drop in the voltage during the charge.  As the voltage rises to a level allowing it to jump the gap, some (but probably not all) of the energy available will be discharged across the gap. 

It seems possible that with this system, changing the spark gap could actually alter the timing.  It would be quite convenient to use this method to adjust timing quickly on a bike; what is the availability and cost of capacitors that will handle this voltage?

I think the high voltage discharge produced by the coil is at least mostly dc.  It's a build up and release of energy.  CDI stands for Capacitor (or Capacitive?)Discharge Ignition.

If ac was coming out of the coil, you would only make use of half of it with only one diode, because you are only rectifying half of the waveform to dc.

The fact that your diode works better one direction than the other is probably due to the polarity of the components working together.  I wouldn't be surprised if the diode is already fried and there is a spark jumping a gap inside the diode.  Got a Fluke?

 

Where I get really foggy on this is what the spark devices are trying to accomplish?  Longer duration?  Is there more power to be gained this way?
 

jaguar

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#3
I think the advantage, other than possibly increasing spark power, is allowing you to advance the ignition some but still having the same timing at high rpm due to the charge delay of the capacitor which would be more significant at high rpm´s than low rpm´s.
By having a diode there, possibly the coil doesn´t have to fight the electrical inertia of the first voltage/current output when the second one happens. The coil outputs two voltage peaks, one when voltage is applied to the coils primary winding, and the second when the primary voltage returns to zero.
I will try to buy enough caps to handle 30Kv and try the experiment again.
 
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#4
I find this all very curious. The fatter spark is achievable in other more conventional means, as is the timing adjustment.

Unless the ign is insufficient, a stronger spark often results in no gain whatsoever.

It is quite easy to design and build an ignition system that makes enough power to kill. My favorite example is the ign on a turbine engine, with high current.

It has been proven time and time again that internal combustion gasoline engines do not need excessive voltage and current to get the job done properly. Most bike ign systems make more and more voltage as the RPM's increase, at least up until the point that one or more of the windings become saturated. So with that in mind, your spark voltage probably varies and will never exceed the capacity of the windings.

Are you testing at a specific RPM or are you using the kickstarter? Using the kickstarter results in widly varying voltages.

Chris
 

Jaybird

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#5
Are you going to try this with a Splitfire? I imagine a turbo-charged Splitfire HAS to absolutely rock! (tic)
 

jaguar

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#6
I was doing it with the kickstarter.
Other than buying an expensive aftermarket CDI for a different timing curve, how does one change that? Of course you can change the rotor (or is it stator) position but that doesn't change the curve.
 
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#7
Jag, I suspect that the timing change available through such tricks is minimal.

Chris
 

motometal

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#8
What't the highest voltage capacitor you can find?  i've worked with 600V and that's about it.  So if you string a bunch together in series, you increase the allowable voltage, correct?  I'm thinking that if there was a 30 kV capacitor, either the plates would be WAY far apart and the capacitance would be tiny, or the dielectric would have to be really good.

 

while we are on the topic, does anyone know why sparks can be different colors?
 

Jaybird

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#9
I'm no Niels Bohr, but doesn't the luminescence of electrons depend on what range of energy is used to excite them, as well as the medium in which the energy transfer is occuring?
 

MrLuckey

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#10
If I remember correctly, spark color is determined by ionization of the of the air moluecules (nitrogen, oxygen, argon, carbon dioxide). A hot healthy spark will more fully ionize all the atoms producing one color while a weaker spark (or one of the same potential trying to jump a larger gap) will ionize a lesser portion or only some of the elements producing a different color of spark.
 

jaguar

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#11
new test results

I found a replacement cable/plug-cap that uses a capacitor and its called HotWires. found it last night in my Sudco catalog. They made some pretty wild claims that make it seem more doubtful. The other night I hooked up a car ignition coil that I think outputs 12Kv. I drove it with 15v switched on and off with a transitor so the setup resembles an older motorcycle points ignition. Anyway, with 15 of the 1Kv caps in series the spark at the plug was more erratic than without the capacitors. So I am pretty much writing this gizmo off.
 
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