Here is a little instruction in case you couldn't install FDE on your device. Recovery doesn't install it well..or..FDE doen't autostart or you just don't have a recovery for your device (as in my case with china noname phone).
-> Download latest FDE zip and extract it.
-> With any root explorer copy engine
folder to /system/
-> Set 777
(check all tabs) permissions to whole engine
folder and what is in there and in every folder content
-> Then get 'Terminal Emulator' app from Google Play store, run it and type:
-> Grant root permission then type:
-> After that reboot your device and in 2 minutes, check log file on path: /sdcard/Android/FDE.txt
-> If there is no FDE.txt log then open Terminal Emulator again and type:
-> Wait it's completion, then check log file again. If it exists, please send it to me to deal with autostart issue for your device. You should run theese two commands every time you reboot your device..
Hope this will help you and you will be happy to see your device runnign fast.