Many domestic, Chinese, and imported automatic cars in the Iranian market are equipped with CVT transmissions. Despite numerous advantages such as lightweight, fewer moving parts, and compact design, CVT transmissions also have their critics. CVT gearboxes are specifically designed to reduce fuel consumption and provide a smooth and quiet driving experience. For this reason, drivers seeking excitement and a more dynamic driving feel usually do not prefer this type of transmission. If you want to learn more about the advantages and disadvantages of CVT transmissions, we recommend reading this article until the end.
What is a CVT Transmission?
CVT, or Continuously Variable Transmission, is a type of transmission system with variable gear ratios. The concept was first introduced by Leonardo da Vinci in the 15th century, but the technology was commercially applied in passenger cars in the 20th century.
Automakers turned to designing CVT transmissions with two main goals in mind: first, to create compact automatic transmissions suitable for light vehicles, and second, to reduce fuel consumption.
In CVT transmissions, there are no conventional gears. This feature makes CVT transmissions known as lightweight and compact gearboxes that don’t take up much space in the vehicle. The gear changing process in this system is done by shifting a belt, allowing continuous and seamless changes. Unlike manual transmissions, where gear changes occur only at specific speed ratios, CVT transmissions are recognized as variable ratio systems because of this continuous adjustment.
How Does a CVT Transmission Work?
To better understand how a CVT transmission functions, it’s helpful to look at its structure. Instead of conventional gears, this system uses two pairs of cone-shaped pulleys, sometimes referred to as “foleys” among mechanics. One pair is connected to the engine crankshaft (input side), and the other pair is connected to the differential and wheels (output side).
These two pulley pairs are not directly connected; they are linked by a metal belt. The engine power is transferred from the crankshaft to the input pulleys, and then via the belt to the output pulleys.
So, how does gear shifting happen in this system? The belt length in a CVT is fixed and does not change. To change the rotational speed of the pulleys, the belt moves up or down along the conical pulleys. Each pair of pulleys moves linearly relative to each other.
For example, if the distance between the input pulleys increases, due to the fixed belt length, the distance between the output pulleys decreases. Consequently, the belt’s diameter on the input pulley decreases while it increases on the output pulley. This continuous adjustment in belt diameter on the pulleys responds to changes in vehicle speed. Thus, without traditional gear shifts, the CVT transmission performs similarly to manual gear changes.
The movement and positioning of the pulleys in this system are controlled by the Transmission Control Unit (TCU). This computer collects and analyzes input signals from various vehicle sensors and issues commands to adjust and synchronize the vehicle’s speed accordingly.
What Are the Advantages of CVT Transmission?
As discussed regarding the structure of CVT transmissions, this system significantly has fewer moving parts compared to manual gearboxes. Although the size of the conical pulleys may vary depending on the engine power, CVT transmissions are generally designed to be compact and suitable for light vehicles. This design is also economically efficient.
Since CVT transmissions have fewer moving parts, the design and manufacturing costs are lower than other transmission types. Moreover, if proper driving habits are followed, the maintenance intervals for CVTs are considerably longer. The design keeps the engine RPM at a level that maximizes torque efficiency. This feature ensures smooth and seamless gear changes in CVT-equipped vehicles. Additionally, CVT transmissions typically offer better fuel efficiency compared to other systems.
What Are the Disadvantages of CVT Transmission?
Since the introduction of the first generation of CVT transmissions in passenger cars, this system has undergone significant technical improvements. Many of the early issues have been notably reduced or resolved. However, CVTs still have some specific limitations.
One of the main limitations is torque transmission capacity. Therefore, sporty or off-road vehicles that require maximum torque generally do not use CVT transmissions. At high speeds, increasing engine RPM can generate considerable noise, which may be uncomfortable for passengers.
Acceleration with CVTs is often less than ideal. Especially when overtaking another vehicle on the road, the system may not respond quickly. CVTs also perform relatively poorly on uphill climbs.
Although CVTs require less frequent maintenance, their parts tend to be expensive. While there is no strict lifespan limit for these transmissions, it is generally recommended to have the CVT system thoroughly inspected every 150,000 to 200,000 kilometers.
Difference Between CVT and AT Transmissions
One important topic to discuss is the difference between CVT and AT transmissions. Both systems are types of automatic transmissions, meaning the driver does not need to manually change gears. However, their structures are fundamentally different.
The AT transmission, similar to manual gearboxes, has fixed gears that shift at predetermined ratios. In contrast, the CVT transmission does not have fixed gears and transfers power using pulleys and a belt. Generally, AT transmissions tend to be larger and more expensive than CVTs, but many drivers prefer the driving experience of a CVT due to its smooth and seamless gear shifts. Additionally, vehicles equipped with CVT transmissions usually consume less fuel compared to those with AT.
Vehicles Equipped with CVT Transmissions
In the Iranian market, most automatic vehicles are equipped with CVT transmissions. For example, Saipa, which aims to offer vehicles at lower prices, uses CVT gearboxes in models like Saipa Saina, Quick, and Shahin Automatic. In the Chinese and imported car markets, vehicles such as Tiggo 5, Tiggo 7, Arizzo 5, Arizzo 6, MVM X22, MVM X33, JAC J4, and Toyota RAV4 are all equipped with CVT transmissions.
Guide to Driving Vehicles Equipped with CVT Transmissions
Driving a vehicle with a CVT transmission is quite similar to driving one with a traditional automatic (AT) gearbox. The main thing to keep in mind is that acceleration may feel less responsive, especially when starting off or overtaking other vehicles. Avoid sudden pressing of the gas pedal during driving, as this puts excessive stress on the CVT belt and can potentially damage the system. Fortunately, in urban traffic, CVT transmissions perform smoothly and continuously, providing a comfortable driving experience without issues.
In Conclusion
In this article, we explored what a CVT transmission is, along with its advantages and features. If you enjoy sporty, fast driving, a CVT might not be very appealing to you. However, for those who prefer a calm and comfortable driving experience, CVT offers a pleasant ride. Importantly, issues seen in earlier generations of CVT have been significantly reduced in newer models, making this technology much more reliable and efficient today.