Can't use smart update (Delta update)
Delta updates work with every file that have a valid delta file for it to update. The binary delta2exe applies that delta file on your old file and updates it to the newer one.

All you need is that delta file which you can get (and is applied directly) with the app CyanDelta  which works for all official releases of CyanogenMod and OmniROM.

If you have the old and the new file you can easily create your own delta file by following the tutorials on how to create delta files: eg. for xDelta