gadam05

The condenser discharges back into the coil giving it an extra "boost". The coil and the condenser form an oscillation or ringing that can be seen on an engine O scope.
 
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I'd love to see that waveform. Charlie Kettering was a genius to come up with this LC circuit, much to the chagrin of the magneto manufacturers
 
tbirdtbird said:
I'd love to see that waveform. Charlie Kettering was a genius to come up with this LC circuit, much to the chagrin of the magneto manufacturers
Click to expand...

primary_ignition_coil_oscillation.png
Well the picture come out the first time but Tom below has one that tell the tale.
 
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tbirdtbird said:
I'd love to see that waveform. Charlie Kettering was a genius to come up with this LC circuit, much to the chagrin of the magneto manufacturers
Click to expand...

I have some better pictures, but they must be stored on my old computor. The sudden drop on the right in the first picture shows when the points close and the cycle starts over again.

The high oscillations on the left show the spark jumping the spark plug. The spark continues until the voltage drops low enough to not be able to jump the plug gap. The next group of oscillations is the coil and condenser bouncing the remaining current back and forth until it dwindles to near zero and the points close to build up the magnetic field for the next cycle.

The second picture is when I switched my scope to SUPERIMPOSED, so it shows the 4 spark plug patterns stacked on top of each other. This makes it easy to compare how each plug is firing compared to the others.
 

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Thank you Mike V Florida and Tom W! So the standard arrangement (applicable per my testing to authentic Ford coils) is internal connection of the secondary (High Voltage) winding to the "grounding" side of the Primary winding and so it has a ready current supply. The coil I described, and first had in my car, either did not have that arrangement or was defective in that respect. It needed to have its outside case grounded. Strange. But in the clear diagram from Mike V Florida we can see how it is supposed to be and why the regular unit does not need firewall grounding of the case. I note the old Ford units had a metal case but modern coils seem to be non-metallic.
Hope this leads to a solution for gadam5.
Rancho
 
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