Odd behaviour between BaseVehicle.getEngineLoudness aand BaseVehicle.setEngineFeature

[frootloopers]

I've been playing with the Driving Skill mod and Braven's Auto Engineering mod while at the same time trying to develop my own mod that allows a player to upgrade features of a car's engine.

 

Recently, I noticed that doing:

>vehicle:setEngineFeature( vehicle:getEngineQuality(), vehicle:getEngineLoudness(), vehicle:getEnginePower() )
then doing >print(vehicle:getEngineLoudness()) will result in a loudness value that is approximately the original / 2.8

 

This also happens with the Driving Skill mod. You can tell without debug by inspecting the vehicle engine, getting in the car, and driving. The loudness will fall sharply even with level one driving.
Does anyone understand why this happens, or where this 2.8 modifier comes from, or if its some sort of bug?

I've also noticed that in Vehicles.lua in the original game files, they multiply engine loudness by (SandboxVars.ZombieAttractionMultiplier or 1) before calling setEngineFeature, but adding this to my own code or the Driving Skill mod's code doesn't make the loudness value equal the original.

 

I've also double checked in vanilla and the engine loudness does not appear to randomly decrease.