Consider renaming the ‘heat-efficient’ fuel devouring furnace to ‘Blast Furnace’
Consider making this ‘blast’ furnace, which consumes fuel at a ludicrous rate, a furnace which produces results not only faster, but generates more finished materials for lower required raw materials. As it is now, aside from speed there is nothing beneficial about this furnace vs the basic furnace.
Example: instead of 1 iron bar per 1 iron stone, perhaps 3 iron bar per 2 iron stone, or 5 iron bar per 4 ironstone, or something similar.
1.5:1 or 1.25:1 ratio