This is to make your Frag gernade to have a fire or flame trail behind it (like a fire Ball )
1) First Open Your Map E.G Dune
2) OPen the Effects Tag
3) Locate effects/objects/granade/frag_gernade/smoke_trail and Open It
4) Change the prt3 to efects/fire/fire
5) Change the Phmo to effects/physics/fire
6) Resign Map