I don't know about the unit you purchased. But, I can probably help you with the electrical theory.
Coils develop voltage based on a turns ratio of the windings/primary to secondary. You can make more voltage by either adding windings to the secondary or reducing windings on the primary. Wire, does have a resistance which creates and energy loss. Adding windings also increases this loss. This makes reducing primary windings look attractive from a wasted energy loss standpoint. However, reducing the primary resistance increases the current demand to energize the coil. As mentioned elsewhere, while the coil is being energized, presumeably with a 12 V source, a 0.8 ohm primary coil will draw 15 Amps (a 0.7 ohm coil will draw 17.14A). This will not, of course, be a continuous draw, but will either be a percentage of the crankshaft rotation, or a timed duration event from some independent measuring device. Multiple spark events would seem to indicate the presence of the latter. Anyway, one thing to consider is if the Gerex triggering device inside can reliably withstand the extra current being demanded of 0.7 ohm coils. A guess would be...probably. But, for how long is unknown without switch device data.
Discharge energy or charge energy?
Another factor of coil selection will be the mode of energy delivery. The stock SOHC4 coils, store up energy before the spark event and release it during the spark event. Some of the more modern ignition systems, deliver the energy to the coil only at the spark event and do not rely on the coils to store the energy, merely convert the voltage level. Such coils do not have the large permeable metal mass needed to store energy. In fact, they need a smaller mass to create a rapid voltage increase at the output. Could the Gerex be an early predecessor of the modern type?
Rather a shame you couldn't get the coils designed to work with that ignition module. You just may have bought yourself a reverse engineering project.
Best of luck!
