Understanding Your Car - Continuously Variable Transmission (CVT)

Driving a car is part and parcel of daily life for a lot of people across the globe. Cars have 2 types of transmissions – Manual and Automatic. Sales of automatic cars have seen a very rapid and increasing rise in recent times. The increase in traffic, changes in perception of the automatic transmission, and improvement of technology are some of the key factors that have led to an increase in this demand. There are majorly 3 types of automatic gear transmissions widely used across cars – Torque Converter, CVT and Dual-Clutch. We are going to make the CVT transmission simple and make you understand it better.

The Continuously Variable Transmission (CVT) is an automatic transmission that works on seamless shifts and unlike a conventional automatic gearbox does not use fixed gears. CVT is also known as stepless or shiftless transmission. Leonardo Da Vinci one of the greatest minds ever and a man way ahead of his time sketched the first stepless transmission way back in 1490! In 1958, Dutch manufacturer introduced the world’s first CVT transmission in a car. Since the turn of the century, the CVT transmission has been widely used across cars globally.

When fuel is combusted in an engine, power is generated. This power is then transmitted to the wheels which then begin turning and move the car ahead. The speed of the engine is different from the real driving speed (speed of the car on the road while driving). An automatic gearbox uses gear ratios to match engine speed and real driving speed. The gear ratios are fixed and range from low to high. The auto gearbox uses the appropriate gear ratio depending on the speed of the car.

A CVT gearbox does things differently. A CVT gearbox does not have fixed gear ratios and operates variably with the speed of the engine. The CVT gearbox is a very basic system that works on the principle of pulleys. The CVT transmission uses 2 pulleys that have variable diameters connected by a belt or chain. One pulley is connected to the engine while the other is connected to the wheels via the transmission. The pulleys used in a CVT transmission are always in pairs. The input pulley is connected to the engine and receives energy from it to drive the output pulley. The input pulley is also known as driving pulley as it drives the output pulley. The output pulley moves when the input pulley drives it and sends power to the wheels which makes the car move forward.

The diameters of the pulleys are variable and become smaller or larger depending on the speed of the engine. This allows the CVT gearbox to work seamlessly and efficiently without having fixed ratios and operating infinitely at any time and at any engine speed. CVTs are of 3 types – Pulley-based, Toroidal and Hydrostatic. Pulley-based CVTs are the most commonly used in cars. CVTs tend to have the infamous ‘Rubber-Band effect’ experienced while driving a CVT car. However, this is not an issue it is caused by the constant acceleration and deceleration of the car. The CVT transmission has the following advantages – 

1. Smooth Shifts.
2. Improved Fuel Efficiency. 
3.  Better Reliability. 

The disadvantages of a CVT are –

1. Expensive Maintenance.
2. Getting used to driving a CVT car may take some time.