There was interesting question on Maxon Cinema 4D area in CGtalk forums
“How to do a smoke ring effect with Cinema 4D”.
Here´s my quick tip.
It´s possible to do a smoke ring in Cinema 4D R12 with
transparent texture on torus object and
animated noise shader in displacer
modifier. Here´s some settings in R12.
I hope you find it useful.
I will propably post file later on.