I went into the Jacobs Electronics website today to see what was there. From what I could determine, the Jacobs units are now varying the spark energy with respect to load and engine rpm, even using a sort of level and accelerometer combination sensor to determine if the vehicle is going up hill. In some applications, using rpm and load to determine when greater spark energy was needed would be beneficial.
One thing I had not seen mentioned in a long time was "Joules". A "joule" is a measure of electrical energy, similar to "volts" and "amps" but not the same. When the first electronic ignition "add-on" kits were around in the early 1960s, they still had breaker points in the distributor, but used them at a lesser voltage to trigger a control box that fired the coil to put the spark to the spark plugs. The lesser voltage across the point set's contact points led to longer point life, they claimed, due to less metal transfer/erosion of the contact surfaces. At that time, there was some debate about how the spark should be--a sudden ZAP or a little more prolonged spark duration with less zap. Many of the companies quoted their specs in a unit of "Joules" and the spark duration in milliseconds. Some engines had different preferences for the way the spark took place, it seemed.
Chrysler had a Prestolite Capacitive Discharge ignition in the early 1960s GM had their AC-Delco CD ignition systems in the later, middle 1960s on various higher performance engines. There was also a pre-HEI electronic ignition on 1972 Pontiacs, but it saw low installation rates for various reasons. Chrysler had their electronic ignition units on the 1972 models and then standard across the board. GM started installing their HEIs in the last couple of months of the 1974 model year.
Interestingly, Oldsmobile had an engine management system similar to the Chrysler Lean Burn system along about 1977, but was a low installation rate item for some reason. I did find one owner that had one and loved the fuel economy it gave his big Toronado.
Back to the Jacobs items . . . On the website, there are some pictures of various sparks at different levels of Joules. No mention of voltage, just Joules. The way the spark plug is set up, with the ground electrode at an angle to the center electrode, plainly illustrates a basic principle of electricity--that it'll jump to the closest ground or follow the path of least resistance. This one principle is what tends to make the multi-electrode spark plugs appear to be overkill or not needed.
The other consideration is that modern engines, and the older ones too to a lesser extent, have to have a reliable spark for each cylinder's firing cycle. That spark needs to happen the same way each time, hitting the same target or one essentially the same each time. If the spark dances around as some spark plugs make it, then it would seem that the "same way each time to the same target" would not happen.
Another situation includes the amount of electrical energy consumed by the spark plug. Some of the more modern designs and materials get more spark from less energy, which could make that old 32KV coil act like a more powerful one, for example.
Along about 1974 time frame, Chrysler had what they called Electronic Ignition II, which came with platinum spark plugs in the New Yorker 440s it was optional on. Best I could tell, the main distinction was the platinum plugs. By that point in time, the engines were running hotter (requiring double heat shields on the plugs) and access to the plugs was getting a little worse than prior years. Having a 50,000 mile spark plug could have been a selling point.
I know that we've all had differing experiences with various replacement parts on our vehicles. What works best for one might not be quite so great on another one, for example. Finding that "sweet spot" for what works can be very rewarding and enhance the ownership experience.
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