As of Buildcraft 3.2.0, they have been renamed to Stirling Engines, as they do not actually require water or steam to function.
Produces: 1 x Stirling Engine
Power SourceEditStirling engines output 1MJ/t while on (given a redstone signal).
The stirling engine runs on burning items and so needs refuelling to continue operation. Burnable items include lava buckets (which the buckets are not consumed) , coal, charcoal, wood, planks, sticks, saplings, crafting tables, chests and bookcases--basically it will burn everything a normal furnace will burn, except cactus and sugarcane. The stirling engine also needs a redstone signal to run.
|Lava bucket||16 minutes 40 seconds|
|Coal/Charcoal||1 minute 20 seconds|
|Wood and Planks||15 seconds|
|Saplings and Sticks||5 seconds|
Stirling engines can be used as a power supply for mining machines. Stirling engines can be connected to each other, or they can transfer power through conductive pipes.
Though it doesn't run much faster than the Redstone Engine, it provides a great deal more power per stroke.
They are your best choice for powering a pump for 1 or 2 combustion engines, while if you are using more, a combustion engine will be needed for the water supply.