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:

* **Stock-Engine** power rating
* **Tonnage**

To calculate the maximum speed of 'Mech use this equation:

(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*.

## References

1. ↑ Piranha Games\MechWarrior Online\Game\GameData.pak\Libs\Items\ItemStats.xml
2. ↑ How screen shake is calculated
3. ↑ Piranha Games\MechWarrior Online\Game\GameData.pak\Libs\Items\ItemStats.xml
4. ↑ How screen shake is calculated