[BUG] Mass ratio calculation for engines causes problems on cars and lightly armored vehicles

[CheezusChrust]

Short Description

On light vehicles (under 2 tons or so it becomes especially noticeable), if you parent your drivetrain, the vehicle drives quite a bit slower than it would if you just welded everything ACF.
With the ability to parent any ACF components, this bug becomes much more apparent.

How to Reproduce

Create a basic vehicle chassis with a total overall mass of under 1000kg - the lighter it is, the more noticeable the bug is. Give it a beefy but heavy engine such as the special 2.9L v8. Make two copies - one with all ACF components welded, and then one with all ACF components parented. The vehicle with parented components will accelerate and reach top speed much slower than the vehicle with welded components.

Additional Information

Currently, at least for light vehicles, I'm better off just welding ACF components for the extra power it gives me, which shouldn't be the case. This can also benefit tankers if they weld-parent their heaviest few pieces of armor.