And heating resistors does increase their resistance but its only a few percent and I don't think that is an issue here..
What I said is not referring to resistors
increasing their resistance by heating. That's futile, we can agree on that. What I meant is
all resistors by their nature become warmer when there's current going through them, indicating they consume energy, it's as simple as that. Hence my statement: little as that may be, my idea of natural conservation of energy tells me that is were the energy goes: up in joules in the resistors.
I have found no confirmation for the hypothesis that resistors give a longer spark duration, not even in NGK's documents, let alone in my handbooks. Again, I'm eager to learn and if there's a
significant longer spark duration, no doubt oscilloscope screens will show us. But for the time being all this is academic hairsplitting IMO. What I can understand, is that there's less oscillating as the resistors act both ways.
The condensor is another story. It's to prevent arcing between the points that switch around 3A which is a lot. A benificial side effect is the up to 300V induction in the primary that helps the coil to perform well.