I'm not sure if this helps, but in my time studying how weapons work I figured out that things didn't work like I expected. The reason being, is that I expected that weapon damage would be determined like this:

Base Weapon Damage * Mark * Skill

But it was actually:

Base **+** (Base/10 * Mark) **+** (Base/100 * Skill).

In other words, rather than all being multiplied together, there were three distinct parts which were added together. You get the exact same skill bonus whether you use a Mark I or a Mark XII, which was totally unexpected to me.

So, it's possible the actual equation for engines follows something similar and it isn't just a straight multiplication of all factors. Anyway, I'm just throwing this out there, and maybe it won't be any help.