if you bail and tower,it doesent count as death.
It does.
From the Help Page:
"Kills per Death = TotalKills / ((Discos * 0.5) + Bails + Captures + Deaths + 1)"
For example: My fighter score tour 129:
K/D 7.59
167 Kills
5 bails
4 ditched
3 captured
13 deaths
0 disco
5+3+13+1 = 22
167/22= 7.59. Et voila!