Engine

Fusion Engines are the powerhouse of a BattleMech and are mounted in the Center Torso.

Engines provide the power necessary to move a 'Mech and fire its weapons. Unlike internal combustion engines, Fusion Engines generate power by fusing hydrogen isotopes (1H) much like the center of a sun. Despite conventional thought, these Engines are not potential mini-nuclear explosions. When damaged to a significant degree they will automatically shut down all fusion reactions and power down the BattleMech. WARNING: To override this shutdown process the default button on all Engines is 'O'.

Engines not only produce power but also have a power loss, which leads to the advent of heat, that needed to be dissipated, thus needing at least 3 Heat Sinks to work.
 * Engines with a power rating of less than 250 require extra Heat Sinks.
 * Engines with a power rating of 275 and higher provide extra slots, that take only Heat Sink (without consuming additional Critical Slots on the 'Mech).

Variants
Each 'Mech comes with its own Standard-Engine from stock. This Stock-Engine defines the maximum power rating of the 'Mechs Engine upgrades, thus limiting its maximum speed (Restrictions Formula).

Engines come in two different variants and a Stock-Engine may be of either type, depending on the 'Mech model.

Standard-Engine

 * Requires 6 Critical Slots only
 * Built for the battlefields, small, sturdy and low-cost, but heavy. A Standard Engine costs less than a comparable XL-Engine, but weighs about double.
 * 'Mechs mounted with a Standard-Engine are less vulnerable:
 * The 'Mech have no portion of the Engine in their Side Torso (RT and LT) and can therefore survive the loss of one (or even both) side torsos.
 * Making only the Center Torso a Critical hit-zone.

XL-Engine
XL stands for "Extra Light", NOT "Extra Large". But these engines do require more space than the standard engines.


 * Expensive - Acquirement costs about triple the amount of a equally rated Standard-Engine.
 * Lighter - Due to the usage of lighter materials, an XL-Engine weighs only half as much as a Standard-Engine of the same power rating.
 * Bulkier - Further occupies 3 Critical Spaces in each side torso, adding another 6 slots to the 6 occupied in the Center Torso.
 * 'Mech is more vulnerable, for their Engine extrudes its bulk into the sides (RT+LT). Destruction of 3 Engine Critical Slots results in the 'Mech being destroyed, therefore destruction of either side torso will result in death.

Clan XL-Engine
Clan XL engines are only found in Clan 'Mechs. The Clan XL is more compact than its Inner Sphere counterpart, taking up 2 critical slots in each side torso instead of 3. Since it takes the destruction of 3 engine critical slots to destroy an XL engine, a Clan XL can remain operational after the destruction of a single side torso (but not both). A 'Mech equipped with a Clan XL will suffer a heat penalty in both capacity by at 40% and dissipation by again 40% with an additional overall speed debuff (including torso yaw speed) of 20% upon the destruction of a side torso, due to PGI.

Light Engine
Light Engines are only found in Inner Sphere 'Mechs. Similar to the Clan XL-Engines, the light engine takes up 2 critical slots in each side torso instead of 3.
 * Expensive - Acquirement costs about twice the amount of a equally rated Standard-Engine.
 * Lighter - Due to the usage of lighter materials, a Light-Engine weighs only three quarters as much as a Standard-Engine of the same power rating.
 * Bulkier - Further occupies 2 Critical Spaces in each side torso, adding another 4 slots to the 6 occupied in the Center Torso.

Historical Footnote about the Engine Table
The Engine weight table does not match TableTop rules, as it includes the Cockpit (3 tons), Gyro (Power Rating/100, roundup) and an adjustment for required Heat Sinks up to the maximum of 10 in Mech Lab for engines rated at less than 250. (See FAQ for more information)

Coming to Speed
'Mechs are restricted on how fast they can go by two factors: To calculate the maximum speed of 'Mech use this equation:
 * Stock-Engine power rating
 * Tonnage

(Power rating / Tonnage) x 16.2 = Max. speed.

Restrictions Formula

 * 1) Maximum-Engine power rating cannot exceed 400 or ~8.5x the 'Mech's tonnage, whichever is lower.
 * 2) Maximum-Engine power rating with (round up to nearest 5 or 0):
 * Light 'Mech = 1.4 x Stock-Engine
 * Medium 'Mech = 1.3 x Stock-Engine
 * Heavy 'Mech = 1.2 x Stock-Engine
 * Assault 'Mech = 1.2 x Stock-Engine

Note: Every 50 ton 'Mech or heavier is therefore only restricted by the multiple of its Stock-Engine rating, since 8.5x its tonnage will always exceed 400.

Example: Limitation by Stock-Engine rating
A Hunchback HBK-4G is a 50 ton medium 'Mech and comes with a 200 rated Stock-Engine. The first restriction placed on it is, that it cannot use an Engine rated higher than 8.5 multiplied by its tonnage (8.5 x 50 = 425). Since no 'Mech can use an Engine rated higher than 400, the first restriction caps it at a 400 rated Engine.

The second restriction says: the Hunchback cannot use a Engine rated higher than 1.3 times its Stock-Engine rating of 200 (1.3 x 200 = 260). This means it cannot use an Engine with a rating higher than 260.

Since the max. Engine is limited by the lower of the two rules, the highest Engine the Hunchback can use is a 260 rated Engine.

Example: Limitation by tonnage
The Cicada CDA-2A is a 40 ton medium 'Mech and comes with a 320 rated Stock-Engine. The first restriction placed on it is, that it cannot use an Engine rated higher than 8.5 multiplied by its tonnage (8.5 x 40 = 340).

The second restriction says: the Cicada cannot use an Engine with a rating higher than 1.3 times its Stock-Engine rating of 320 (1.3 x 320 = 416 rounded down to 415). Since no 'Mech can use an Engine rating higher than 400, the second restriction limits it to a max. Engine rating of 400.

Since the max. Engine is limited by the lower of the two rules, the highest rated Engine the Cicada can use is a 340 rated Engine.