Is there any way to lower the sound of the engine, but keep other things like the sound of the tires starting to lose traction and screech loud?
Do you mean muffled sounds for in-cabin? If so, that's probably going to be implemented at some point. But otherwise, the game would not be realistic if you could change the volume of everything.
um, its not very realistic that every car shares the same generic sound clip either, but hey, thats none of my business.... anyway, i was able to edit the "factor" values in the \content\vehicles\common\sounds\default_sounds.sbeam to reduce the engine sound to my liking. I found that by reducing the engine sound, i could better hear when the tires were just starting to screech and lose traction in a curve, giving me more time to ease off.