CVT Explained: How it Works and the Best Cars

A Continuously Variable Transmission, or CVT, is unique compared to other automatic transmissions such as AMT, DCT or a Torque Converter, quite simply because it has no predefined gear ratios. Instead, a CVT has the ability to recreate an infinite number of gear ratios. The first CVT was invented before the 1900s, and this kind of transmission is not just used in cars, but has a widespread application in other areas as well such as power tools.

When it comes to cars, the first CVT was used around 1960. However, its most high profile use was in 1993 when the Williams racing team fitted their F1 car with a CVT transmission, and it was immediately banned because of its outright speed advantage over its competitors. In modern day cars, CVTs are tuned for offering the maximum amount of smoothness and efficiency. Keeping that in mind, we have compiled this article which offers an in-depth look at a CVT and its advantages and disadvantages, for new or used car buyers.

What is a CVT?

A CVT can be considered the simplest type of automatic transmission. It uses two pulleys that have variable diameters. These act as the gears, and the variable diameter allows them to mimic different gear ratios. One pulley is connected to the engine whereas the other is connected to the shaft that drives the wheels. Finally, both pulleys are connected by a strong belt or a metal chain, which allows the engine pulley to spin the one attached to the output shaft. 

However, some modern hybrid cars use an eCVT, which operates differently using planetary gears than a conventional CVT with a pulley design. An eCVT is fundamentally different to a CVT and are often incorrectly classified as the same.

How does a CVT Work?

A Continuously Variable Transmission (CVT) operates by continuously adjusting its gear ratios to match driving conditions. A CVT can be tuned for either efficiency or performance. In most mass-market vehicles, CVTs are optimized for efficiency. This means the engine runs at its most fuel-efficient RPM, while the CVT’s pulleys adjust their diameters seamlessly to alter the effective gear ratio, thereby changing the vehicle’s speed.

The adjustment of pulley diameters is controlled by a Transmission Control Unit (TCU). Like other automatic transmissions, the TCU relies on data from multiple sensors to determine the optimal pulley configuration for any given situation, ensuring smooth and efficient operation. The most important sensor are:

1. Throttle Position Sensor - Measures the position of the throttle
2. Vehicle Speed Sensor - Uses wheel speed to calculate car speed
3. Engine Speed Sensor - More commonly known as RPM or revolutions per minute
4. CVT Belt Tensioner Sensor - It is used to maintain the optimum tension in the CVT belt
5. CVT Pulley Position Sensor - Sends information to the TCU about the position of pulleys

A CVT transmission can use more sensors in addition to the ones listed above for collecting more data to allow the TCU to make more informed decisions when controlling the CVT belt/chain and pulleys.

Advantages of a CVT

CVTs were initially popular in foreign car markets, but over the years, they have made their way into Indian cars as well due to the advantages:

1. CVTs are smooth:. The design of a CVT allows for seamless gear ratio changes without the jerk of a gear change. This makes CVTs extremely smooth.
    
2. CVTs are efficient: The TCU in a CVT can be programmed to allow the engine to run at its most efficient RPM, thus consuming the least amount of fuel. Alternatively, the TCU can also be programmed so that the engine spins at an RPM where it makes the most amount of power, and the pulleys change their ratios accordingly. 

Ultimately, CVTs offer engineers flexibility in tuning and smoothness in their operation.

Disadvantages of a CVT

With the advent of modern day automatic transmissions, CVTs aren’t all that advantageous as they one used to be:

1. Rubber-band Effect: As the diameter of the pulleys changes rapidly and the length of the belt is changed, the power delivery feels like it has been stretched like a rubber band. This is quite prominent when a sudden burst of power is demanded by the driver, like in the case of a quick overtake.
    
2. Durability Concerns: There have been durability concerns with CVTs over the years, but modern advancements in technology have largely mitigated them. However, if you are looking to buy a used automatic transmission car which has a CVT, then, you should be wary about a worn out belt or pulleys. For such cases, always take a test drive and if you feel that the engine is making power but all of it is not being transmitted to the wheels, then, you might be dealing with a worn out CVT.

The problems with modern day CVTs are marginal. However, if you expect mass market CVTs to offer a highly sporty driving experience, then you are better off looking at cars with DCT or Torque Converter automatic gearboxes.

Top Cars with a CVT in India

CVTs are found in mass market cars that are positioned above budget models. CVTs are mostly found in cars that try and offer a smooth driving experience.

Is a CVT Right for You?

A CVT transmission is similarly priced as a DCT or a Torque Converter, so it doesn’t offer any real price advantage over them. However, a CVT is highly smooth and is therefore ideal for those who like to be chauffeur driven. Alternatively, it is also a good choice for those who drive with a light foot and don’t consider performance a real criteria in their car buying decision. On the flip side, if you do consider performance a key criteria when buying a car, then you can explore other types of automatic transmission options.

Conclusion

A CVT’s main characteristic is smoothness, and thus if a smooth driving experience is number one on your list of parameters when buying a car, you should consider going for a car with a CVT transmission over a manual or other kinds of automatic transmissions.