1-your gta v has to be updated in new patches otherwise you will have no sound
(the "prototipo" car must exist in the game, thats why i changed the sound)

2-go to :grand theft auto v/update/x64/dlcpacks/AlpineGT/dlc.rpf/common/data/levels/gta 5

3-extract the vehicles.meta and open it whith notpad

-search for       <audioNameHash>TURISMOR</audioNameHash>

4-change "TURISMOR" by "PROTOTIPO" to have the original sound

5-(optional/YOU HAVE NO SOUND) change "TURISMOR by "any car name you HAVE IN YOUR CURRENT GAME"

6-save it and take it back where it was.