January 23, 2017 at 3:40 PM
If you are shopping for a used car, you may have heard the term Continuously Variable Transmission (or CVT), but do not fully understand what it means.
Here we explain what CVT actually is, how CVT works, and explain the benefits of CVT to the car and the environment. Plus, find out which used cars are currently sold with CVT.
Continuously Variable Transmsision (or CVT) is a lesser-known type of automatic transmission. It is also referred to as single speed transmission, which means the transition between gears is seamless. Instead of using a box full of gears, it utilises a pair of pulleys - which is why CVT is refered to as a transmission, rather than a gearbox. A continuously variable transmission technically doesn't have gears at all; instead it's like having one gear that's variable across all driving situations
Usually fitted in supermini and compact cars, a CVT gearbox is simple in construction and compact in size, making it a more cost-effective gearbox choice for car manufacturers over regular automatic transmissions. Car makers currently using CVT gearboxes include Toyota, Nissan, Honda and even Audi.
However, just as with a traditional automatic gearbox, the car automatically changes gears, depending upon your driving speed. Therefore, there is no need for a clutch pedal. A car with CVT will only have a brake and accelerator pedal. A car fitted with CVT will be more expensive than its manual counterpart, as it would be if you opted for a traditional automatic gearbox,
Leonardo DaVinci sketched the first CVT in 1490 and CVT gearboxes have been around since the early days of the automobile, but it was Dutch carmaker DAF's Variomatic gearbox that saw Continuously Variable Transmission become commonplace in cars in the 1950s. However, technological limitations made CVTs unsuitable for engines producing over 100bhp. Then in the late 1980s and early 90s, Subaru offered CVT in their Justy mini-car.
Because engine revs aren't related to wheel speed in cars fitted with CVT, early models such as those built by DAF, had a familiar whining noise as engine revs increased, but road speed built slowly. DAF cars also didn't have a reverse gear, instead the CVT box simply worked in reverse. So these cars were going backwards and forwards at the same speed.
As previously mentioned, a CVT gearbox is simple in its construction, with two cone-shaped pulleys connected by a v-shaped drive belt. One pulley is attached the the engine, whilst the other is connected to the car's wheels. As you press the accelerator pedal, the engine revs increase. This causes the cone to move depending on the power. The second cone then adjusts accordingly so that the tension in the drive belt is remains the same.
Because the two pulleys are moving independently, there are no set gear ratios as you would expect in a standard automatic or manual gearbox. Therefore, CVT is a single-speed unit with infinite gear ratios available - meaning you'll never feel your car shifting between gears.
Because of the non-complex construction of CVT, it doesn't have many moving parts making it fairly reliable. Because CVT is usually fitted the smaller cars with low engine capacity, cars running CVT are usually fairly unstressed. Providing the gearbox is kept well lubricated, and you stick to a regular maintenance schedule, then a CVT gearbox should be just as reliable as a conventional automatic or manual transmission.
The only notable reliability issue with CVT is that the drive belt between the two cone-shaped pulleys can wear out. This can lead to slip, which will be obvious as the engine revs, causing the car to accelerate slower than normal.
Using CVT is also great for the environment, not just for your car. It is estimated CVT gearboxes give 8% better fuel economy than a standard automatic gearbox, no matter what speed you are travelling at. As your car will be operating at the optimal speed and correct gearing, your car will be more efficient.
You will be using and burning less fuel, which is beneficial to the environment. When you drive a car with a manual gearbox, you obviously change gears in relation to your driving speed. This is not the case with CVT, as it is constantly altering the speed of the wheels in relation to the engine, giving your car more mileage and helping the environment at the same time.
CVTs are fitted into many vehicles manufactured in Japan and CVT is becoming more popular with drivers , with more choices than ever before. Here's some of the used cars on the market in the UK today which may feature continuously variable transmissions:
Audi A4; A5; A6
Ford Fiesta, Focus C-Max (1.6 L TDCi 110 PS model only)
Honda Insight; Jazz; HR-V; Civic and Accord.
Jeep Compass 2.0L, 2.4L;Jeep Patriot 2.0L, 4.0L
Lexus CT 200h; IS 300h; ES 300h
Mercedes A-Class; B-Class
Mitsubishi Lancer; Colt; Outlander and Mirage
Nissan Micra; Murano; Qashqai; Cube and Juke
Rover 25; Streetwise and 45.
Subaru Forester; Impreza; Outback; Legacy; Stella; R2 and R1.
Suzuki SX4; Forester; Legacy; Impreza and Outback.
Toyota Corolla; Prius; RAV4; Verso; Yaris and Avensis.
Toyota's Hybrid Synergy Drive (HSD), which is used in hybrid models such as the Prius and Lexus IS 300h, uses a form of CVT gearbox as part of its innovative hybrid system. This has a split power delivery so that the car's engine is either driving the wheels or sending power to the battery.
So, as you can see, there are many cars on the market available with CVT. If you want a more economical car, that is effortless to drive and easier on the environment, then choosing a car with CVT is a wise move.