MJ

MJ is the energy that BuildCraft 3 uses. MJ stands for Minecraft Joules. It is generated by any kind of Engine and can be used by any kind of BuildCraft machinery. Many types of energy can be converted to MJ by using Engines, however, transforming MJ into other power types is a more complex process, and requires the usage of energy conversion machines found in other mod packs. MJ can travel through Conductive Pipes and Redstone Energy Conduit. 

Generation

MJs are made by all types of Engines. Redstone Engines generate MJ just with a redstone signal, but others like the Combustion Engine need Fuel or other resources to produce MJ. Redstone Engines are used mainly to power Wooden Transport Pipes and Wooden Waterproof Pipes, due to their low outputs, a higher-tier engine is advisable in order to power machinery.

List of Engines

Name	Max Output (MJ/t)	Source Mod
Biogas Engine	5	Forestry
Blulectric Engine	23+	RedPower 2
Combustion Engine	6	Buildcraft 3
Commercial Steam Engine	4	Railcraft
Electrical Engine	14	Forestry
Hobbyist's Steam Engine	2	Railcraft
Industrial Steam Engine	8	Railcraft
Magmatic Engine	4	Thermal Expansion
Peat-fired Engine	1	Forestry
Redstone Engine	0.05	Buildcraft 3
Stirling (Steam) Engine	1	Buildcraft 3
Steam Engine	2	Thermal Expansion

Transportation

Some Golden Conductive Pipes carrying MJ. The cyan beam in the pipes is MJ.

Engines can place their MJ into a machine, a Wooden Conductive Pipe (which can be then attached to other Conductive Pipes), or a Redstone Energy Conduit with the arrow pointing out of the machine.

Conductive Pipes are like wire for MJ to travel trough. Stone Conductive Pipes have a 5% energy loss by each block, and Golden Conductive Pipes have a 0.5% energy loss by block. When MJ is traveling trough a Conductive Pipe, a cyan beam is seen inside the pipes. MJ traveling a Conductive Pipe is seen in the right of this page, note the cyan beam inside the pipe.

Redstone Energy Conduits do not have a distance related energy loss. Instead, there is a loss for how many inputs points the energy travels through. Anytime energy enters a Redstone Energy Conduit network, 5% of the energy is lost.

Thus any power line longer than 10 blocks is more energy efficient if Redstone Energy Conduit is used, while purely from an energy efficiency frame shorter cables are better as Golden Conductive Pipe.

To see more information see Conductive Pipes

Transformation

Other power types can be converted into MJ. EU, IndustrialCraft 2's power, can be converted into MJ by using an Electrical Engine. Blutricity, RedPower's 2 power, can be converted into MJ by using a Blulectric Engine, which takes blutricity and outputs MJ. MJ can be converted into EU by powering a Magma Crucible with Netherrack or Cobblestone inside it that generates lava, and then put that lava into a Geothermal Generator or a Thermal Generator; the Magma Crucible will take MJ and the generator will output EU, with an efficiency that depends on what resource is melted in the crucible and which generator is used to extract EU. The most efficient version of this process allows the resulting EU to be converted back into MJ with a properly upgraded Electrical Engine with no loss.

EU Conversion

Lava Source	Generator	MJ per Lava	EU per Lava	EU per MJ
Cobblestone	Geothermal Generator	24,000	20,000	0.83
Cobblestone	Thermal Generator	24,000	30,000	1.25
Netherrack	Geothermal Generator	12,000	20,000	1.67
Netherrack	Thermal Generator	12,000	30,000	2.5