BorgWarner's dual-clutch DSG (direct-shift gearbox) transmission systems have been showing up in Volkswagen and Audi vehicles since 2003. The system utilizes two clutches to select gears, allowing for smooth, uninterrupted power delivery. The clutches are electro-hydraulically actuated, allowing for virtually instant gear changes and control logic that pre-selects the next required gear. While BorgWarner's original DSG design has allowed for greater fuel-efficiency over traditional automatic transmissions, it has had room for improvement. The original design is a wet-clutch system, meaning the clutches operate in a bath of oil to keep temperatures down and eliminate wear. The oiling system requires large pumps to keep up the constant flow through the system and it also creates hydraulic drag that affects efficiency.
However, with recent announcements coming out of the BorgWarner camp, it is apparent they are still on the leading edge of dual-clutch transmission development. The company is slated to provide systems for the upcoming Nissan GT-R and BMW M3. These are high power output applications that would be hindered by BorgWarner's original DSG design without improvements. For these next generation systems the wet-clutch system has been changed to a moist-clutch system requiring less lubrication and therefore a smaller oil pump. This also reduces hydraulic drag on the system, thus reducing drivetrain losses. The clutch materials have also been improved for heat transfer and wear properties. The use of materials that do not degrade with friction or waste mechanical energy through heat generation allow the clutch design to live in these more stressful environments and to do so more efficiently.
[Source: BorgWarner via CNNMoney.com]