Five years ago, Volkswagen began manufacture of the first mass-production Dual Clutch Transmission (DCT) in the world: the 6-speed Direct Shift Gearbox (DSG). The names of the units are interchangeable. Since then, over one million 6-speed DSGs have been sold. VW now has developed another all-new transmission, the world’s first 7-speed DSG to be produced in high-volume. For many drivers, VW says this could signify the final turn away from conventional transmissions, because this new DSG can do everything better than a manual gearbox, being more fuel efficient, sporty and comfortable.
The most prominent component of the DSG is its dual clutch. In comparison to the 6-speed DSG, there is no "wet" clutch in the new transmission – a clutch immersed in an oil bath – rather, there is a "dry" clutch, another world first for DSG technology. This and other engineering modifications led to significant improvements to the DSG’s efficiency. The result: Further reduced fuel consumption and emissions values, even greater convenience and driving fun.
Of all the world's car-makers, Volkswagen seems most interested in getting this technology out to the drivers of the world. This automatic transmission system offers benefits including small improvements in gas mileage and emissions, through an end to the wasteful "idle" during gear changes in automatics. It also makes for better handling because the drive wheels are always directly connected to the power being transmitted by the engine on both up and down shifts.
In theory, it all makes sense, which is more than some automotive technologies. Years ago, at a magazine long lead for some new VW products, I sat next to one of the company's top engineers at a dinner held during the event. We spoke about two specific technologies, and I'll never forget the conversation that evening, little thanks to the wine which was pouring throughout the evening, something which absolutely effects Europeans much less than Americans, and that's from decades of personal testing and observation. (Photo - VW Eos).
This very Germanic engineer, whose name I remember as, "Herr Professor Doctor Somebody",
explained to me how a liquid which VW used in their all-wheel drive system (then-dubbed "Syncro") actually thickened as it got hotter, exactly the opposite of what normal folks like me expect any liquid to do. Apparently pure vegetable oil does the same thing, but that wasn't the topic that evening. In another posting I'll tell you more about how the strange reaction of this specific fluid made VW's Syncro system work.
The other thing we spoke of was "flame propagation", which is the term engineers use when describing the explosion which occurs in an engine's cylinder when the air/fuel mixture is ignited by the spark plug. And how this relatively small explosion can have a part in propelling a 3,000 pound piece of steel and plastic and whatever to speeds over 300 miles an hour (in the case of a rail dragster or funny car in drag racing). Now, that might not a big deal to you folks under 40, but when we had this conversation, there was no such thing (yet) as a computer simulation of this incredible physical act; engineers, after 100 years, were still just guessing at what was really going on thousands of times a minute in the motors they were building. The engineer told me something which I also won't soon forget: Speaking about flame propagation, he told me, "It is a very simple technology, but also very difficult". Who could argue with that? Now, more about the DCT/DSG.
We found some of the following information in howstuffworks.com, and we'll throw in our own comments when we think it'll help, and maybe to make the tech stuff a bit less dry: Charles "Boss" Kettering, the engineering genius of General Motors, invented the world's first electric starter for cars, first used on the 1912 Cadillac, doing away with the extremely difficult and very dangerous crank starter. (Photo - The VW dual clutch system - exploded view).
The first fully automatic car transmission, called Hydra-Matic, was introduced many years later, in 1939, just one indication of how difficult it was to create. It was first used on the 1940 Oldsmobile. In fact, in a weird precursor of what was to become of his life, the man who is known today as the "Godfather of the Pontiac GTO", Jim Wangers, was photographed behind the wheel of the first Olds with that automatic at the 1939 Chicago Auto Show, and the photo ran in newspapers across the country and probably around the world. Wangers was about 10 at the time, and he told me the photographer must have thought he was a "cute kid" and it made a fun photo. No one can overstate the important of those two inventions to the worldwide acceptance of cars, and Americans can, and should, still be proud that they were both developed by GM.
The automatic transmission, introduced in 1939, switches to the optimum gear without driver intervention except for starting and going into reverse. The type of automatic transmission used on current cars usually consists of a fluid device called a torque converter and a set of planetary gears. The torque converter transmits the engine's power to the transmission using hydraulic fluid to make the connection. For more efficient operation at high speeds, a clutch plate is applied to create a direct mechanical connection between the transmission and the engine (which some readers might recognize as the "1:1 gear ratio").
In 1970, the US Environmental Protection Administration (EPA) was created by an initiative undertaken by American President Richard Nixon, who would find a few years of his own administration missing just a few years later, which were never seen again. (Photo - Schematic of VW DSG electrics).
Due to its creation, for the first time in the history of cars, trucks and motorcycles, there were hard
numbers which vehicles had to meet as far as mileage, emissions, the kind of materials used in making vehicles of all sorts and much, much more. But first, meeting the all-new, first-time mileage goals and emissions figures took help from every engineer on every car company's staff, not only in the US, but at every car-maker worldwide planning on selling cars in the US.
In many ways, car-makers in Asia and Europe had an easier time of meeting the mileage goals than their Detroit brethren, mostly because of the traditionally high cost of gasoline in those countries. Thanks to that, highly-efficient small, high-revving dual overhead cam engines had been developed, in many cases, decades earlier; meeting the new emissions goals was difficult for every car-maker, and many European companies left the US market because of the costs of developing the technology needed to meet the EPA's emissions goals. But in both Europe and Japan, car-makers which had been building small and efficient cars for their home customers suddenly found themselves at an advantage in the US market, and the first oil crisis of the early 1970s bore that out. Funny-looking small cars, many with strange-sounding names, were finding their way into garages all over America. Suddenly, a foreign-made car was no longer a sign of wealth and sophistication, but simply of someone trying to save a few bucks at the pump ... and going to the pump less frequently.
America's car-makers put every engineer at their disposal to work on meeting these EPA goals. This is the main reason American cars of the 1970s and '80s are some of the worst ever produced by any country. Because overseas companies, from Europe to Asia, had faced many of these issues previously due to the high prices of gas in their countries, America cars got "left behind" in those years, and it has taken until only recently for most cars made by the former Big Three to be on or at least near a par with those engineered in Europe and Asia. Also, car-makers quickly discovered that it was a lot easier and less expensive to "up size" cars and trucks rather than "down size" them; most US car-makers needed to make smaller and lighter cars and trucks, while companies from the UK to Japan enjoyed making larger cars which they could sell for much more money in America, in addition to the smaller and less-expensive vehicles they already were building for their home markets. (Photo - All-new VW Touran minivans, introduced at recent Chicago Auto Show).
All-new computer technologies, which were fast-developed to answer the EPA's demands, found their way into Detroit. This rapid introduction of microprocessor-controlled electronic sensors enhanced the performance of all vehicles overall, and of automatic transmissions still more. Data about engine speed, exhaust pressure and other performance characteristics, many of which had never been studied or measured before, in fact some even never known-of before, were now being sent to a processor which controlled the changing of gears and the clutch plate in the torque converter via electrical switches, or solenoids.
New (and now legally-necessary) approaches to transmission design combined the best features of manuals and automatics to provide more efficient ways of channeling engine power to the wheels. A 'manumatic' transmission (such as Porsche's 'Tiptronic') is an automatic with an added manual-shift mode. Another all-new transmission has begun appearing in the past few years, too, called a Continuously Variable Transmission (CVT). CVTs use a belt connecting two variable-diameter pulleys to provide an unlimited number of ratio changes and uninterrupted power to the wheels; CVTs offer better fuel efficiency than conventional automatics, which can only change the transmission ratio by shifting gears. The CVT-equipped cars we've driven are easily-identified by a loud "whine" interior sound and a feeling for the driver that takes the vehicle right to the point where you'd next expect to feel a solid, normal "shift", up or down, but the whine just gets louder and the "thunk" of a real shift never comes. But car-makers love the CVTs because they weigh less and are cheaper and easier to build and even repair than a conventional automatic. That's a lot of reasons to love these units, and we all better get used to finding them in our new cars and trucks, if you don't have one already. (Photo - Schematic of VW DCT/DSG hydraulics and mechanicals).
Which brings us to our Dual Clutch Transmissions, aka Direct Shift Gearboxes. A sequential manual
gearbox (SMG), developed for very sophisticated race cars, uses computer-controlled actuators to operate the clutch and change gears when prompted by the driver; both manual and automatic modes are possible, and there is no clutch pedal.
The dual clutch transmission (DCT) or direct shift gearbox (DSG), substitutes dual clutches for the conventional single-sided clutch to transfer power from the engine through two parallel paths; the gearbox features two sets of gears, identical to those in conventional manual transmissions — one set being the odd gears (1st, 3rd, 5th) and the other the even gears (2nd, 4th, 6th) — the gears must be shifted in sequence, and power to the wheels is never interrupted.
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