Useful Car Tips

Dual-Clutch Transmissions Explained

November 07, 2019
Automatic transmissions are the most popular transmissions in the world, equipped in a variety of vehicles of all sizes. They’re inexpensive to produce, generally uncomplicated, and most importantly, are easy to use. In fact, your car probably has an automatic transmission, too. There are many types of automatic transmissions, and yours could be a traditional torque converter, a CVT (continuously variable transmission), or even a Triptronic. But what about a DCT? You may have heard the term DCT before, and it’s possible that a DCT is the type of automatic in your vehicle. DCT stands for dual-clutch transmission: a transmission that’s similar to a manual, but can still shift gears automatically, of course. So what is the point of a DCT, or really any of the myriad types of automatic transmissions? Each has certain advantages and disadvantages that make it more suitable for certain applications, and with a DCT, that is no exception. Although primarily used in super cars, sports cars, and performance cars in general, DCTs have also seen some use in non-performance sedans, hatchbacks, and SUVs. The next time you go car shopping, you may just stumble upon a DCT, so it’s important to know the basics: what it is, how it works, and why it could be right (or not right) for you.


Since a DCT is a type of automatic transmission, it of course has the ability to automatically shift gears without any input from the driver. This is where the similarities with an automatic all but end, as a DCT is much closer in mechanical operation to a manual transmission. A DCT uses at least two clutch discs, one for even-numbered gears and one for odd-numbered gears. The gears shift in order—much like a sequential transmission—but do so automatically, although a manual shifting mode is commonly available For example: you’re shifting from 4th to 5th gear. In this scenario, the even-numbered clutch will be prepared to disengage 4th gear while the odd-numbered clutch will be prepared to engage 5th gear. As you can see, the nature of this design means that the next gear is always ready to be shifted to, which results in incredibly quick gear shifts. How quick, exactly? Sometimes shifts can be accomplished in as little as 8 milliseconds—much faster than any manual transmission.


While all DCTs operate the same way, there are actually two different types: wet and dry clutch. In wet clutch DCTs, two multiplate clutches are bathed in oil in order to dissipate heat that builds up on the clutch plate. By contrast (and as the name implies), dry clutch DCTs utilize two single plate clutches which are dry, meaning oil is not used. Wet clutch DCTs are designed for use in high torque engines, which sports cars and performance cars in general are likely to have. More heat is produced in these engines so consequently, a wet clutch becomes a necessity for reliable operation of the transmission. On the other hand, dry clutch DCTs are used in low torque engines which do not require the same cooling that their wet clutch cousins do. Although dry clutch DCTs can handle less torque, they tend to be lighter and offer increases in fuel efficiency.


So, now we know that DCTs can shift incredibly quick and handle a lot of torque, what are some drawbacks to their design? In reality, there are few disadvantages with this type of transmission. Drivers used to traditional automatics may simply find it necessary to make a few minor adjustments when driving a DCT. This includes no more inching at a light and keeping your foot firmly on the brakes while on an incline. If you’re used to driving manuals, know that you don’t have to put a DCT into neutral when stopped at a light. Some general jerkiness may take some getting used to as well.


Aside from these relatively drawbacks, DCTs are stellar transmissions, particularly for performance vehicles. If you’re looking for a basic commuter, a car with a torque converter or CVT will probably get the job done just as well or even better. Still interested in a DCT? You’re in luck, as many performance cars have taken advantage of this type of transmission. Among them are stellar cars like the Volkswagen Golf GTI, BMW M4, and Porsche 911. Oh, and a Bugatti Veyron, if you have a couple million dollars lying around. Sure, a manual transmission may be more suited for most performance cars, but if you can’t get (or don’t need) a manual, a DCT is the next best thing!
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