VVT is an inlet variable timing valve technology. DVVT can be said to be an upgrade of VVT, a variable timing valve technology with air intake and outgassing. CVT has nothing to do with the two, it's a non - pole gearbox. More oil saving, shift without a sense of frustration.
All the variable valve timing technology is just a new name for different manufacturers in order to avoid infringement. This phenomenon is more serious in Japan. Almost every auto manufacturer has such a series of techniques. The name is very fancy, and its structure is only a small change. The working principle is the same, all in order to improve the performance of the engine and make the fuel fully burn.