This option is disabled by default in GSCE, how to reactivate it is to rename the image file responsible for this function, it is called "SPARK" (but do not remember the extension), is located in the sub folder "GameData \ Vehicles" - Only this, see an example:
// Enable sparks by increasing the "Max" variable for Reaction=spark. Also set
// "Sparks=1" on appropriate terrains. Also check player file entry "Vehicle Sparks".
//
rename to anything that isn't sparks.tga (like "sparqs.tga" or "sparks.tgaa"), you can also just move to another folder or delete it, should work either way...