When it comes to picking a car, you typically have a choice of two transmissions – manual or automatic.
Complicating the matter, however, is the option of a CVT, or continuously variable transmission, which in practice functions similar to an automatic, but does so in a very different manner.
This is how a CVT differs from an automatic gearbox, and what the pros and cons are of both.
The differences
There are a few different types of automatic gearboxes, but one of the most common types is a dual-clutch.
This works by having two separate clutches that are responsible for partial transmissions from the engine – typically one handles the odd-numbered gears while another handles the evens.
One gear will always be engaged by the engine, and the dual-clutch will keep the next gear pre-selected and ready to be swapped in automatically without input from the driver when the in-use gear is decoupled.
Consequently, the chief advantage of a dual-clutch is its fast shift times, hence they are often touted as a selling feature on high-performance vehicles.
They are, however, quite expensive and are normally reserved for up-market vehicles, though they have also made their way into more conventional passenger cars, such as in the Haval H6.
A torque converter (TC) is another form of automatic, and this application makes use of a fluid coupling letting the motor operate partially independently from the gearbox, which allows the car to keep the engine running even as it comes to a standstill.
The TC itself connects to a flywheel, letting it rotate at matching speeds, and as this speed ramps up, torque is generated, which turns the gears which in turn move the wheels of the vehicle.
The main benefits of a TC transmission are two-fold – firstly, the fluid in the mechanism leads to better cooling, and secondly, the converter can provide a high amount of torque when accelerating from a standstill.
On the other hand, the downside of a TC gearbox is that it has a worse fuel consumption, owing to relative inefficiency of the drivetrain and transmission operating at slightly different speeds.
However, both these types of automatic transmissions use cogs and clutches to facilitate physical gear changes, making the fundamentally different from a CVT.
A CVT gearbox takes the concept of an automatic even further by not having any gears, at least in the traditional sense.
Instead, a CVT uses a set of two pulleys drawing power from the engine, and the width of these pulleys can be increased or decreased to vary the amount of torque drawn to the wheels from the engine, hence the term “continuously variable.”
The theory behind a CVT is that it affords much greater accuracy in matching the vehicle’s inputs in comparison to a transmission with a set number of gears.
Consequently, one of the biggest selling points of a CVT is that it provides much better fuel consumption, as it should rarely allow for the engine to run at a very high RPM.
This fuel efficiency is why you’ll often see hybrid models with a CVT, such as the Toyota Corolla Cross Hybrid.
CVTs are also often lighter than other automatic transmissions, owing to there being fewer moving parts.
Another touted benefit of a CVT is that, because it lacks hard gear changes, it offers a much smoother driving experience, particularly in heavy traffic conditions.
However, this is also one of the reasons why many motorists are not a fan of CVTs, as the continuously adjusting transmission can lead to a somewhat unengaging driving experience.
Because a continuously variable transmission is always trying to run the car at optimal efficiency with steady engine revs, it can make for a monotonous engine tone with little in the way of the vehicle drama that comes with a shift in gears.
A more tangible limitation of a CVT is that it is not as responsive as other gearboxes, particularly for high performance, as it takes time for the pulley band to adjust to the new input.
They also tend to be more expensive to replace than conventional automatics.
Keyword: CVT vs Automatic – What you need to know