Continuously Variable Transmission Vs Dual Clutch

Contents

• Torque converters

• Dual Clutch Transmission (DCT)

• Continuously-Variable-Transmission

• Special mention: Automated Manual Transmission (AMT)

• Which is best?

Automatic transmissions have come a long way since the dawn of the first torque converters. Driving with only two pedals was once considered a luxury in the mid to late 20th century. However, as technology progressed and manufacturing got more efficient and precise, automatic transmissions became more reliable and in some cases, better than the traditional manual transmission.

Over time as well, the options that manufacturers can use to outfit their automobiles have grown. Apart from the traditional torque converter, there are now dual-clutch transmissions (DCT), and Continuously Variable Transmissions (CVT), and even – the less common – Automated Manual Transmission (AMT) that populate spec sheets of many different automobiles. However, which of these options are the best, and should it make or break your purchase?

Torque converters

Between the three, torque converters are among the most common and oldest design for an automatic transmission. Most modern cars have at least 4 gears. Torque converters can also be affordable or highly-engineered. From the most basic like in the 4-speeds found in the Toyota Rush and Wigo to high-performance ZF transmission as found in the Toyota Supra. Torque converters are among the most versatile automatic transmission types, and they are also among the most durable often lasting long stints without needing service, but of course, your mileage may vary, and if you do need a service, there are a lot of mechanics that can work on a torque converter due to its familiar and tenured design in the automotive industry.

Some of the cons of the torque converter have been addressed in modern cars. Back then, these transmissions didn't get you the best fuel economy, but with some clever engineering and some modern enhancements, torque converters can be some of the most economical transmissions provided the engine it is mated to is equally geared to be economical. The likes of the Suzuki Ertiga prove that you don't need a fancy transmission to get great fuel economy figures, however, the ratios are fixed, so if you are running a lower-powered car with a 4-speed automatic, then you may find that it takes quite a while to get up to speed due to the tall gear ratios meant to keep engine revs down, and fuel economy figures up.

Dual Clutch Transmission (DCT)

More common among high-performance cars, the DCT is known for quite a few things. A good DCT locks into place and holds the power and torque coming from the engine securely, all while delivering razor-sharp shifts. Brands like Porsche, are known for their PDK system, which many enthusiasts swear is like a bolt-action rifle. Crisp and snappy shifts are a trademark feature of a DCT provided it's been engineered properly.

However, at slower speeds, a DCT could fumble quite a bit especially if you are dealing with stop-and-go traffic. The transmission could even feel numb and not as responsive in traffic especially in economy cars where everything is built to a price point. Though the transmission should be engineered to take the abuse, you may find that some systems aren't as tuned or geared for life in the city. Some dry DCTs from some brands are known to wear out prematurely when exposed to hellish city traffic. You also want the right kind of DCT for your car, with a wet DCT being more desirable than a dry system.

An example of a car with a wet DCT is the Geely Coolray. With up to 7 speeds to play with and an oil-bathed transmission, you can expect it to be durable if not more durable than a dry DCT. Shifting is also slightly smoother thanks to the lubricant in the system. There are a few exceptions, but if a DCT is not on a high-performance vehicle more often than not it won't shift lightning-quick, or have the crispness of a bolt-action rifle. It'll all boil down to the manufacturer's design and how aggressive they want the DCT to shift and lock in the gears.

Continuously-Variable-Transmission

Moving on to the gearless option in the lineup, we have the CVT. Comprising a belt and two pulleys, the CVT is the best transmission in theory. Minus the torque limitations and power limitations of the transmission type, the CVT is the fastest and most efficient transmission that you can put in your car. The reason is, it keeps your car at the optimal powerband to achieve the fastest and most efficient acceleration possible. Most gasoline engines achieve peak power around 80% of the way to redline, and the CVT is geared to keep the engine revving where the most power is made. You usually see CVTs in smaller cars with smaller engines, however, even turbocharged models are seeing this transmission like in the Honda Civic RS Turbo with its 1.5-liter inline-4 turbo motor. If you're more traditional, the CVT will also allow you to have simulated gear ratios if there are paddle shifters or a manual mode on the lever. This feature locks the transmission and gives the driver the feeling of banging up and down gears, which are good in theory if you want to induce engine brake or control your engine speed like a normal automatic gearbox.

Although, that's not the case because most CVTs have a tendency to feel rubbery. While you can get a good throttle response, if you wring out the engine you won't get that surge of torque,  instead, you'll get a very linear and predictable pull which isn't the most exciting in a low-displacement passenger car. However, where the CVT does show its worth is in fuel economy in the city. It's also good to use in stop-and-go traffic because the response is similar to that of a torque converter, but you won't get that nice locked-in feel when you're at speed like a DCT. Another con of a CVT is that it might not handle torque all too well. That's why diesel engines don't use it because the amount of torque produced by a diesel motor could make the transmission slip. Older CVTs are also known to be brittle, using a belt instead of a chain like most modern CVTs. While the chain is a good improvement over the old belt-driven units, the chain is still prone to slippage, and can even damage components inside the transmission. Failure-rate for the CVTs is now few and far between unless the engine is tuned to produce more horsepower and torque, beyond that of the CVT's durability ratings.

Special mention: Automated Manual Transmission (AMT)

If you want the durability of a manual transmission but with the convenience of an automatic, then you could opt for a car with an automated manual transmission. Good luck finding one though, as these transmissions are a bit costlier to produce and a bit on the rare side. One of the only models in the market to come with an AMT is the Suzuki Dzire, but under Suzuki's nomenclature, it's dubbed the Auto Gear-Shift Transmission or AGS. Essentially, it's a manual transmission with a machine doing the gear changes for you.

The downside is that some of these transmissions can get quite complex, so finding a person that can fix a transmission like this will be half easy and half hard. We say half easy because the manual part of the transmission is easily worked on with a clutch assembly being easy to source. However, the automated part of the transmission might be harder to fix because complexity means repair difficulty. Also, don't expect these types of transmissions to be smooth. In our experience we had to drive the Suzuki Dzire like we were driving a regular manual transmission car, letting off the gas between gear shifts or suffering through some jerky motions.

Which is best?

That really depends on the car you want the transmission on. There are applications where a hardier transmission is necessary like on a diesel pickup truck hauling a lot of cargo. If smoothness is needed, then a more refined torque converter or a CVT will do the job better than an AMT, or DCT, but here's a quick rundown of our findings in dealing with these different types of transmissions.

In terms of fuel economy, it really depends on the engine if the fuel economy figures of the car could stand to be better mated to the right transmission. In theory, a CVT is the most fuel-efficient among the three, and in our testing, we've seen torque converters do well with fuel economy.

For durability, the best transmission is the torque converter or the traditional automatic. CVTs have fewer moving parts, but the chain drive is not as durable as hard gears. When exposed to more power, the transmission tends to slip or get damaged. Meanwhile, DCTs and AMTs have a lot of moving parts, which means a lot of things can go wrong, and there are wear components in these types of transmissions that need to be replaced once worn out.

For more spirited drives, the best-performing types are the DCTs and torque converters. however, smoothness is another factor that you have to consider, and DCTs don't fit the bill and can be a little jerky to use. Meanwhile, CVTs and Torque converters are known to be rather smooth with the former being the smoothest-accelerating among the selection of transmissions here, plus CVTs help maximize the power in economy cars. You can expect more performance out of a smaller engine and a CVT than a smaller engine and a 4-speed automatic. The reason being is that the engine can be in its optimal powerband at any point that the driver chooses to bury the throttle. So it depends on what you are looking for.

So what's the best all-around automatic transmission? It has to be the torque converter automatic transmission. It's durable, it holds power pretty well, and it can even shift quickly if it is engineered well and designed for performance. You will run into some cons with this type of transmission if you do get a smaller-displacement engine with less power. In that case, a CVT would be a better choice if you had a 1.5-liter engine without much torque or horsepower. In that case, a good small-displacement transmission would be the CVT. A lot of manufacturers like Toyota and Honda have outfitted some of their best-selling subcompact sedans and hatchbacks with CVTs. For example, the Honda City used to come with a torque converter, but a CVT is now standard throughout the range. The same goes for the Toyota Vios. From a 4-speed automatic, the sedan went with a CVT as standard in the later generations.

So that leaves the two other transmissions out of the top 2, DCTs and AMTs. In truth, these transmissions can get really good, however, they could be expensive to repair and are quite jerky in stop-and-go traffic. At least in the Philippines, a DCT isn't the most optimal of choices, however, once you are out of traffic, driving a car with such a transmission can be very enjoyable. So it goes to preference and what compromises you are willing to make, however the most versatile among the transmissions listed are the Torque converters, whether affordable or expensive.

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Source: https://www.autodeal.com.ph/articles/car-features/cvt-vs-dct-vs-automatic-whats-difference-and-which-better

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