CVT and Direct Shift-CVT: why the common name does not describe each transmission

Useful to know

The transmission connects the operation of the engine with the movement of the wheels by a certain gear ratio. In CVT, the name denotes a continuously variable transmission. This is a different idea from choosing only a few fixed degrees. Toyota introduced Direct Shift-CVT as its own development in this group. [1] It is important that the general concept and trade name differ. From the fact that two cars are described as CVT, it does not follow that every their mechanical part and every behavior are the same.

In the 2018 presentation, Toyota described goals such as limiting mechanical losses, a wider transmission ratio range, and a better response to a mode change. [1] These are different tasks that need to be solved together. Transmission is not just a means to write down a certain number of gears in the catalog. It is involved in the way the engine operates at different speeds and loads, and affects the feeling of starting and accelerating.

The feature of Direct Shift-CVT is the separate gear for starting. Toyota describes it as a way to improve transmission at low speeds and reduce the load on the belt part. [2] Therefore, this particular system should not be explained only by the simplified image "two washers and a belt". The general scheme may be useful to begin with, but the specific mechanisms added change the way it works in different sections of the driving mode.

The technical page also looks at the geometry of the belt, the size of the washers, and their inertia. [1] These details show why improvements to a transmission may be related to several interacting parts. The published comparisons are relative to a certain previous system and period. They do not have to become a universal value for economy of any car with a similar name. For a correct comparison, it should be clear what exactly is being tested and with what frame of reference it is being compared.

Imagine a person looking at two used cars. The uniform general abbreviation in the listings is insufficient to evaluate the device and service. It is necessary to establish the exact transmission by the model, version and documentation. The prescribed service and actual history are then checked. It is a method of gathering information, not a sentence for a particular technology. The general internet claims for all CVTs cannot replace the specific data for the car under consideration.

It is useful in a technical conversation to ask three separate questions: how the attitude is changed, what realization is used and how it is served. Thus, principle, construction, and condition do not mix. Direct Shift-CVT is a good example of how a manufacturer can develop a familiar transmission family through an additional mechanism and changes to the core elements. Understanding this makes catalog names more informative when read along with the exact version and purpose of the whole drive.