Twin Clutch SST

Twin Clutch SST (Sport Shift Transmission) is the brand name of a twin-clutch transmission developed by Mitsubishi Motors. The first application to incorporate the system will be the new 2007 Lancer Evolution.

Overview

Mitsubishi's automated manual transmission employs dual clutches to realize power transmission efficiencies on a par with a normal manual gearbox while also allowing slick and swift shifting. Allowing rapid shifting up and down through the gears, Twin Clutch SST delivers greater acceleration while also returning better fuel mileage thanks to its high-efficiency power transmission mechanism. The new transmission also features three operating modes tailored to different situations: from around-town drivability to instant-response and sporty motoring on the open road.

Operation

Twin Clutch SST puts odd (1st, 3rd, 5th) and even (2nd, 4th and 6th) gears on separate input shafts, each connected to an individual clutch. With both clutches under precise system control, this arrangement allows extremely fast, smooth and lag-free gear changes with no interruption in power delivery. Using clutches instead of a torque converter to transmit power makes the Twin Clutch SST simpler in structure and reduces power transmission losses for higher transmission efficiency that leads to improved fuel mileage.

Drive modes

Twin Clutch SST allows switching between three shifting programs — Normal, Sport and S-Sport.

• Normal mode

For use around town and other normal driving situations, Normal mode uses relatively low-speed shift points to deliver unobtrusive shifting together with optimum fuel economy.

• Sport mode

For use when driving in the mountains or when engine braking is required, Sport mode scheduling uses higher shift points and quicker shifting to deliver instant throttle response.

• S-Sport mode

Compared with Sport mode, S-Sport mode scheduling keeps the engine turning at higher revs, allowing even faster shifting.

References

1. "Mitsubishi Motors develops S-AWC vehicle dynamics control system & Twin Clutch SST automated manual transmission", Mitsubishi Motors website