First dual-clutch auto tranny to handle the output of a consumer based performance automobile. [xfloat=right]http://www.cleanmpg.com/photos/data/501/2008_European_BMW_M3.jpg[/xfloat]Wayne Gerdes - CleanMPG - Jan. 26, 2008 2008 BMW M3 Convertible -- 400 + HP and almost 300 Ft-lb’s of torque through an automatic transmission that allows superior performance, better FE and weighs just 40 pounds more than the manual it replaces. BMW debuts the world’s first Double Clutch Gearbox with Drivelogic developed for higher speed, higher power output consumer based engines. Unfortunately, it is currently only available on the new European M3 Coupe, M3 Sedan, and M3 Convertible. The M’s double-clutch transmission is a seven-speed gearbox designed for high power throughput. Compared with a conventional automatic or manual transmission, the new gearbox ensures optimum shifts and better acceleration while at the same time reducing fuel consumption. The transmission does this by seamlessly shifting gears without power interruption from a stop to any speed with or without driver input. The standard automatic mode is available with the gearshift in D (drive). Two manual modes are also available while in S (Sport) mode which allows shifting via either the paddle shifters on the steering wheel or with the gearshift in a straight and sequential manner. Racing sets the stage for the consumer The double clutch gearbox was first developed for motor sports where every tenth of a second is crucial. Over the years, this unique transmission concept has proven its worth in the same way as the sequential gearshift used in Formula 1. The ability to shift up at WOT without the slightest interruption in the application of torque allows even professional drivers to shave a few fractions of a second off their best times at the track. Until now, consumer based double clutch manumatic gearboxes could only be used with lower revving and relatively low torque engines. For the first time, the benefits of a double clutch gearbox are now available to the consumer regardless of the size or power of the engine. How does a double clutch manumatic transmission operate? Double-clutch transmissions combine two gearbox components in a common housing with the same compact dimensions as a conventional manual gearbox. The “heart” of the new M double-clutch transmission in technical terms is formed by the two oil-cooled wet clutches. One of the two clutches is for the even (2, 4, 6), the other for the uneven (1, 3, 5, 7) gears and, in addition, for the reverse gear. While driving, one of the two clutches is always closed, the other is open. When accelerating – and when shifting down – the clutches are activated in an alternating process, one after the other. When shifting gears, therefore, the first clutch opens just as the second clutch is closing. This ensures an absolutely smooth, comfortable and at the same time incomparably fast gearshift without the slightest interruption in the flow of power. This interaction of two clutches ensures an unparalleled rate of gear change in particular because the transmission control unit pre-selects the next gear. The transmission ratio is matched ideally to engine and road speed and the gear is held in waiting for immediate operation. The key to the entire process is that it takes only a few milliseconds, meaning that in the time even a skilled driver takes to press down the clutch pedal the M double-clutch transmission with Drivelogic has easily completed the entire process of shifting gears, continuing to accelerate in the next gear higher up. With the process of engaging and disengaging the gears continuing in a smooth flow, the positive engagement of the engine to the transmission is not interrupted, allowing the driver to set off smoothly, comfortably and, in particular, to shift up at an incomparably fast speed. When down shifting, a double-clutch transmission works exactly the same. The only difference is that the electronic transmission control makes the process of engaging the clutch smoother and softer to prevent the rear wheels from being slowed down too suddenly. Negatives? Special cooling requirements are required to handle the M’s double-clutch transmission under extreme conditions. Due to the possibility of high thermal loads during high power output, the M’s transmission fluid is kept within an optimal temperature range by using both a standard engine coolant based transmission cooler and an additional air/oil cooler to avoid excessively high temperatures. A positive to the design is that the transmission fluid is also heated by the engines coolant system during initial start-up allowing the transmission to reach normal operating temperature faster in colder climates. This helps to reduce frictional losses in the warm-up phase and saves fuel in the process. More gears allowing higher efficiency Compared with a conventional automatic or manual transmission, the M’s double-clutch transmission allows greater fuel economy and cleaner emissions using the same engine with the same power. This is primarily attributable to the more direct connection between the engine and the transmission, the lack of RPM cycling between shifts during accelerations and the ability to run taller gears without a standard automatic's power robbing frictional losses. With the advent of track tested dual clutch transmissions for the masses offering superior performance and higher fuel economy over and above either a standard manual or automatic transmissions today, it should only be a matter of time before we see these advanced but lightweight drivetrains in far less expensive and more main stream vehicles in the near future.