BTW, is that really a film you just made?
Yes, made it yesterday. It's my very first film, actually. Fairly challenging to do camera work, the narration, and provide the actions all at the same time. I need work/practice/improvement in all areas. But, I'm proud to announce I never once received an electrical shock...or dropped the camera.
Perhaps I still have the attention priorities in the right order.
I re-read the Wikipedia write up about ignitions which has this discussion about the secondary and primary being connected to the battery.
The ignition coil consists of two transformer windings sharing a common magnetic core -- the primary and secondary windings. An alternating current in the primary induces alternating magnetic field in the coil's core. Because the ignition coil's secondary has far more windings than the primary, the coil is a step-up transformer which induces a much higher voltage across the secondary windings. For an ignition coil, one end of windings of both the primary and secondary are connected together. This common point is connected to the battery (usually through a current-limiting resistor). The other end of the primary is connected to the points within the distributor. The other end of the secondary is connected, via the distributor cap and rotor, to the spark plugs.
There are nearly endless variations on how circuits can be arranged and work, even if they do the same basic end functions.
The coil in the Wiki description is a single ended coil. While basically the same construction internally, the wire terminations of the two internal coils are different. Were you to use that style of coil on the SOHC4, you'd need 4 of them, or have a spark distributor system as found in the automotive world. Some single ended coils may have only two obvious connections; power in to the primary, (switched by the points), and the wire to the spark plug. The other two connections can be the metal case of the coils, connected internal to both primary and secondary windings, where the metal body is electrically attached to the engine block. While the primary of the coil needs to attach to both battery terminals, the secondary does not. Energy generated within the secondary only needs a current path between the two output connections. The spark plug base needs only an electrical connection to the coil body for the circuit to complete. An added connection to a battery terminal is irrelevant, but convenient from a mechanical arrangement perspective.
The SOHC4 coils have independent connections for all four wire leads. The primary gets power from the battery, and the points interrupt the primary current between coil and the battery neg terminal, which out of convenience, is the engine block.
The SOHC4 coil output leads are actually both ends of the secondary coil. Those ends have to be connected together for current to flow in the secondary coil. This path is completed by the wires, the spark plugs, the plasma in the spark gap, and the cylinder head. Again, the cylinder block is connected to the battery neg terminal out of mechanical convenience, but this connection is irrelevant to the coil secondary function of producing spark.
I guess I am misinterpreting this difference between the Honda ignition and an automotive coil circuit as to how each delivers spark. I know my memory is not perfect, but I know I had to touch a plug to the exhaust header to insure I had spark on my '65 Ford V8. Never tried pulling two plugs and connecting a wire between them.
That wouldn't have worked on the Ford, as you would not have had a connection back to the other end of the secondary winding of the coil. The exhaust manifold did, probably through the engine block/intake manifold, or some-such path.
Cheers,
