By using two or three electronic pickups and ignition boxes and double ended coils from motorcycles or late model cars, wouldn't it be possible to build a waste-spark system for most older four and six cylinder engines and get rid of the distributor cap, rotor and so forth? Is there a good reason why this isn't done very commonly?
It has been done by experimenters, earlier, and there is an aftermarket kit that I have seen that puts one small coil per cylinder. That kit is not too cheap, but allows the optimum in custom timing.
You could retain the distributor and use it only for the timing function of a waste spark system. Or, you could time the coil pack from the crankshaft pulley.
There is probably limited demand for such a system for older cars, but technologically is it very feasible and would not be too complicated to build.
By the way, you specifically mentioned a waste-spark system, and I gave you a general answer. On the waste spark system, one firing of the coil is wasted on a cylinder that is not in the power stroke position. It serves no purpose, other than to simplify the design a bit.
Multiple coils were first considered to prevent overheating of the main coil, and electromagnetic saturation effects, thereby better ignition. Going to capacitive discharge systems, getting rid of the Kettering points requirement, etc vastly improved ignition systems.
The one coil per plug system I mentioned is not a waste spark system, but is distributorless and is about as efficient as ignition systems need to be.
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