Trying to understand vehicle speed (Darkness falls and/or Vanilla)

[ActuallyTony]

I've been playing Darkness Falls with friends and someone has a Rat motorcycle while I had the GNX. Rat has a velocityMax of 17, 17 and the GNX having 15, 18 and they both had super charger mods installed. It seemed like the Rat was quite a bit faster than the GNX so I went down a rabbit hole trying to understand vehicle speed.

 

The 4x4 is just a hair faster than the motorcycle despite having the same velocityMax, both values. My first assumption was motorTorqueMaxQ value, assuming it got you to max speed faster but the Rat was much lower than the GNX so that didn't make sense.

 

My question is, does anyone know how exactly speed is calculated? velocityMax seems to be the main component but something else is used with it.

Second question is what does the buffs VehicleVelocityMaxPer/VehicleVelocityMaxTurboPer actually do in terms of value? The super charger sets these values to 2 and it seems like it's a multiplier, so does it just flat out double speed?