Dual-clutch transmissions, also known as double-clutch transmissions or twin-clutch transmissions are a design derived from traditional manual transmission engineering. It is a system that uses two distinct clutches for even and odd gear sets. They have been a popular choice of car manufacturers in the last 10 years, thanks to their known advantages. Dual clutch transmissions exhibit smooth automatic operation when doing daily driving chores, as well as super quick shifts when flooring it. The demands of circuit racing, however, require more high performance.
Take a look at this video provided by Nate Vincent of FCP Euro. It shows a GTI TCR race car comparing its used DSG dual-clutch transmission with a fresh sequential transmission that will be used on the track this 2019. The most notable difference is the weight as the clutch and flywheel of the sequential transmission is almost 100 pounds lighter than the dual clutch transmission. Additionally, fewer gear shafts are also used by the sequential. Combined with the light flywheel, you get less rotating mass and much less weight for an engine to work.
Furthermore, dual-clutch transmissions employ helical-style gears, contrasting with a sequential’s straight-cut gears. This innovation translates to minimized power loss in the axles. Dog teeth connectors rather than synchronizers are also used to shift gears, pushing gears together. With all these advantages, then why aren’t sequential transmissions on production cars? Well, the main reasons are: they lack smoothness for daily driving, they make a lot of noise, and they don’t go the distance. By comparison, dual clutch systems last longer, are quieter and smoother. But if speed is all that mattered, such as on the race track, then the obvious winner is the sequential transmission.