In ProjectE, they used to have a burn time; you could actually smelt a lot of items with it.

Coal smelts 8 items

2 Coal (16) makes 1 Redstone (16)
2 Redstone (32) makes 1 Gunpowder (32)
2 Gunpowder (64) makes 1 Mobius Fuel (64)
2 Mobius Fuel (128) makes 1 Aeternalis Fuel (128)

Mobius Fuel should smelt 64 items
Aeternalis Fuel should smelt 128 items