Burnt taste in a fluid soaked coil
I call it the stove top pot principle
Take a metal pot, put water in it...set it on electric coils on a stove, turn it on high
Watch the coils...the coils NOT in contact with a heat wicking device (the pot and water) will glow red = very very hot, the part that does have the ability to push heat (induction) won't turn red (aka pushing heat into the pot and water), however the water in the pot will start to heat, as it heats closer to its boiling point it will start to boil (atomize) however if you put a thermometer in your water even at rolling boil the temperature will NOT climb above its boiling point, why...well the heat energy of the water is dissipated as steam (vapor) and the heat IN = heat out
You can continue to push heat to the pot until the water in the pot boils away, then watch as the heat in the coils below the now empty pot start to heat up to glowing (getting very very hot)
The coil in your tank/atomizer/whatever is the EXACT same principle only teeny tiny compared to the stove top
You heat the coils, if it were not for the e-juice absorbing the heat energy and boiling (vaporizing) the little coils would glow red, now the hotter you make those coils the FASTER it can turn the juice to vapor, but can the wicking material keep up with the rate the steam is going out (huge clouds of vapor = huge amounts of juice going poof, can your wick keep up)
What happens when your wick no longer can keep up with the vaporization, it heats up and starts glowing, when the temperature of that wire exceeds the caramelization temperature of your e-juice you get caramelization of the sugars and stuff in the e-juice, hotter still you get carbonization (aka the black sooty nasty burning of the juice)...and that tastes like a nice ol' charcoal briquette
Carmelization