To expand on this point:
Right now the game is a bit broken. Only CT and Head shots will take a mech out. That and overheating causing an explosion. XL engines do give 3 crit slots to the right and left torso besides the center torso. Destruction of a Torso location (losing all Internal structure after your armor is gone on that location) will (is suppose to) kill your mech because it receives 3 engine hits.
This is the reason why Standard engines can technically be better, because they keep your R and L torso's clear for more weaps and equipment and makes your mech less vulnerable when its hurt bad.
Hence, XL's are more expensive because they are more vulnerable being bulky. They also cost a lot more when your mech is utterly destroyed. To clarify you can actually take damage in your R and L torso that is critical, it may not be the engine if you have other items equipped there such as heatsinks, ammo or even weapons.
If you wish to upgrade your speed the engine rating you need is the following formula. I use my Raven as an example.
Forumula : mech weight x desired walk speed = engine rating (Running speed is always 1.5 of walk)
Raven 2X has a speed of 5/8 or 50kmph walking, 80kmph running , tonnage is 35 tons
35t x 5 = 175. Means I need a 175 standard engine to obtain 50kmph walking speed
To upgrade the Raven to its XL version, (which has a standard speed of 6/9), I need a 210 XL engine
35t x 6 = 210. I want the XL because XL engines cut my engine tonnage in half, giving me more room for goodies.
- rolly(Former) SSI Co-Commander, Clan Admin
(Former) WoT Division Admin
Head of Office of Strategic Services [Retired]