What is CVT?

From Edmunds.com

Our staff, as well as other automotive enthusiasts, has noticed an ever-increasing level of interest about a new/old technology called CVT (continuously variable transmission) and its burgeoning rise in the automotive world.

We say new/old because CVT has actually been around since 1886 but has only recently begun to find its way into production automobiles.

CVT's promise, both as a boon to fuel economy and as a low-cost alternative to conventional transmissions, has prompted us to revisit the topic.

Since our article "CVT for You and Me" appeared, a number of automakers have brought new CVT-equipped vehicles to market, and more are on the way. We felt now was a good time to take a closer look at this innovative--and time-tested--technology.

As we mentioned above, CVT has been around for more than a hundred years. However, until recently, it was reserved for industrial applications: running lathes or light-duty drill presses, for instance. With the introduction of improved materials, such as high-density rubber belts, advanced hydraulics, and more recently, high-speed sensors and microprocessors, the stage was set for CVT's rise in the automobile.

CVT's design advantages lie not only in its efficiency but also its simplicity. It consists of very few components. A continuously variable transmission typically includes the following major component groups:

• A high-power/density rubber belt
• A hydraulically operated driving pulley
• A mechanical torque-sensing driving pulley
• Microprocessors and sensors

That's it.

Because of this simplicity in design, CVT offers some advantages over traditional transmissions, although it also has certain drawbacks. For instance, its belt-driven orientation limits its application; until recently, cars with engines larger than 1.2 liters were considered incompatible with CVT. More and more, however, CVTs that can handle more powerful engines are becoming available, such as the V-6 power plants found in some Nissan and Audi vehicles.

CVT's design advantages lie not only in its efficiency but in its simplicity.

Other disadvantages include its larger size and weight.

Still, in the right situation, CVT's advantages outweigh its disadvantages. Less complexity and fewer moving parts theoretically mean fewer things to go wrong and maintain.

The first U.S.-sold production automobile in the world to offer a CVT transmission was the Subaru Justy GL, from 1989 through 1993. The engine in that car was 1.2 liters.

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