These days, more cars are using continuously variable transmissions (CVTs) in place of conventional automatic and manual gearboxes. Unlike other transmissions, CVTs don’t use gears and instead use a variable range of ratios to transfer engine power to the wheels. Does that make them more efficient than manual transmissions?
CVT is more efficient than manual transmission because it can always select the optimal gear ratio. This allows the engine to maintain a constant and optimum speed, even when changing gears. A manual transmission can’t match the efficiency of a CVT, even if you’re an experienced driver.
This article will explain how CVTs work to help you understand why they’re more efficient. We will also tackle other benefits of CVTs and uncover why not everyone is a fan of them.
Why CVTs Are More Efficient?
Imagine two identical cars cruising at 60 miles per hour (96km/h):
Car A has a CVT, while Car B has a manual transmission. The CVT in Car B allows it to cruise at a lower engine speed compared to Car A because the CVT can always find the ideal engine speed to facilitate its pace. On the other hand, Car A can use its final gear to optimize efficiency, but the engine will still rev faster as the car increases its speed, thereby making the CVT more efficient.
An engine’s power output varies throughout its rev range which means that peak power is only available at certain engine speeds. CVTs can keep the engine speed to produce the most power and not lose their momentum with gear shifts, which improves efficiency.
You’ll find that the fuel consumption ratings of cars with CVTs are generally better than that of their manual transmission variants. Take the Honda Jazz, for instance, Carwale claims that the manual transmission variant gets a fuel mileage of 39.0 miles per gallon (16.6km/l), while the CVT variant does 40.2 miles per gallon (17.1km/l).
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How a CVT Works?
There are different CVTs, the most common of which uses two cone-shaped pulleys with either a high-power rubber or metal belt running between them. One pulley, known as the driver pulley, is connected to the engine’s crankshaft, while the other one is mounted to the rest of the transmission and is known as the driven pulley.
The driver pulley is where engine power is initially transferred. Once the driver pulley starts rotating, it also causes the driven pulley to turn, transferring the power to the drive shaft and allowing the wheels to move.
What makes a CVT continuously variable is how the gap between the pulley’s cones can change diameter depending on the driver’s throttle input. The variable distance between the cones affects the size of the loop where the belt circulates each pulley; as it gets bigger on one pulley, it gets smaller on the other one to always keep the belt tight.
When the loop on the driver pulley is small and the one on the driven pulley is big, it creates more torque similar to lower gears. As the loop on the driver pulley increases, the one on the driven pulley decreases, making more speed similar to higher gears. The countless combinations between the size of these loops are why they say CVTs have an infinite number of gears.
To better understand how CVTs work, you can watch this video on the Lesics YouTube channel, illustrating what goes on in a continuously variable transmission:
The Benefits of a CVT
The absence of physical gears inside a transmission does have a few more advantages aside from making a car more fuel-efficient.
Here are some benefits a CVT has over other transmission types:
CVTs Operate Within the Engine’s Maximum Powerband
By continuously operating within the engine’s powerband, CVTs ensure that they more consistently achieve peak performance, making accelerating, passing other vehicles, and climbing steep inclines a more effortless affair.
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CVTs Are Light and Simple
Because CVTs use fewer parts, their construction is less complex and lighter than other transmissions. A CVT’s simplicity also means it doesn’t cost much to manufacture. This also makes them cheaper to fix, and the weight reduction benefits your car’s performance.
No Gears Means No Gear Hunting and Shift Shock
Regular automatic transmissions are sometimes prone to gear hunt. They struggle to select the most appropriate gear based on the driving conditions, which causes the transmission to change unnecessarily from one gear to another.
A conventional gearbox is also prone to shift shock, where flooring the gas pedal causes the transmission to downshift quite harshly.
You will never experience gear-hunting or shift-shock with a CVT since it doesn’t use physical gears. A CVT will operate smoothly regardless of how abrupt your throttle inputs are because they can change ratios without you noticing it.
CVTs Are Easy To Drive
A car with a manual transmission requires more driver interaction as you have to depress the clutch pedal and move the gear lever with every gear shift.
CVTs provide you with the ease of using a conventional automatic where you simply have to put the car into drive while the transmission takes care of shifting gears for you.
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What You Should Know About Driving a Vehicle With a CVT?
Despite their inherent benefits, many car enthusiasts avoid CVTs as they claim it robs them of the driving sensations they typically get from a manual or regular automatic transmission. Aside from driving dynamics, CVTs are not as easy to maintain.
Below are typical traits of CVTs that can be a disadvantage in driving and general maintenance.
The Rubber-Band Effect
Good driving dynamics depend significantly on how well a car can respond to the driver’s inputs. Most CVTs don’t react as quickly compared to other transmissions.
In some cases, latency occurs as the CVT doesn’t immediately deliver power after the driver floors the accelerator. This delay is known as the rubber-band effect and occurs due to friction loss of the belt between the pulleys.
No Sporty Feel
CVTs may be easier to drive than manual transmissions, but some drivers long for more engagement with their cars.
Aside from the lack of engagement in driving a CVT, the power it delivers doesn’t feel linear or proportional to the driver’s inputs.
When you floor the gas pedal of a car with a CVT, the engine speed increases and stays within its optimum RPM (Revolutions per Minute), which leads to a droning sound. But apart from the noise, it causes the driver to perceive a disconnect between them and the car.
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High Maintenance Cost
CVTs may have fewer parts and be more straightforward construction than other transmissions, but that does not mean they are cheaper to maintain.
The pulleys in CVTs undergo immense pressure, and too much torque can cause the belt to slip.
If and when there are issues with a CVT, repairing them isn’t always an option as they usually have to be replaced.
Fortunately, there are products such as the Lubegard 67010 CVT Recharge & Protect on Amazon.com, which can prolong the life of your CVT by protecting belts, chains, and pulleys from excessive wear.
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CVTs Are Getting Better
Car manufacturers are aware of the disadvantages of CVTs and are constantly improving the way they perform, particularly when it comes to the driving feel. CVTs have come a long way in production vehicles, and the difference between how they drive compared to regular automatics is far more negligible.
Many manufacturers have now developed their iterations of the CVT — Hyundai/Kia has the Intelligent Variable Transmission, and Subaru has their Lineartronic CVT. In a nutshell, these transmissions feel more like conventional transmissions by simulating gear shifts or the sensation of shifting.
Toyota also has its Direct-Shift (K120) CVT, which uses a physical first gear (also known as launch gear) before transitioning to the belt drive. This transmission setup promises a better response when taking off from a dead stop.
The growing popularity of CVTs can be attributed to their ability to improve gas mileage significantly. CVTs offer many more benefits aside from efficiency but could still be more popular, especially amongst car enthusiasts.
Fortunately, manufacturers are constantly innovating and have reached a point where many people can hardly distinguish between CVT and regular automatic drives.
A CVT may be costly to maintain, but if you factor in fuel savings, that might just be a price many are willing to pay.