Xtrac calls its new transmission a “hybridized automated manual” and says it will allow high-powered supercars and luxury sedans to meet strict fuel economy and emissions regulations not planned until 2020.
The key to the technology is an integrated electric motor, which allows a vehicle to travel at speeds of up to 95 mph on electric power alone, after which the engine kicks in. The seven-speed gearbox offers multiple driving modes, including gas only, electric only and hybrid modes, and the gearbox has an overall ratio spread of almost 6:1.
While this is nothing new, Xtrac’s design allows torque infill from the electric motor up to fourth gear during hard acceleration and in all gears up to a threshold speed during low speed driving when its desirable to keep the engine revs low, thus improving vehicle efficiency.
The term ‘torque infill’ is the application of additional torque through the transmission to the wheels during gear changes, where in a conventional transmission the torque is interrupted to allow the shift to complete. This means the transmission is much smoother than typical automated manuals, which remains one of the biggest criticisms of the design.
Of course, dual-clutch transmissions don’t suffer from the power interruption either, though Xtrac says its gearbox is much lighter, less complex and more efficient.
The ability to provide torque to the wheels independent of the engine also reduces the energy required to be absorbed by the main drive clutch, which means a smaller clutch is possible. The transmission can handle engine torque capacities ranging from 590 pound-feet to 737 pound-feet dependent on vehicle weight and the particular application.
Xtrac plans to showcase its hybridized automated manual transmission at the International CTi Symposium and Exhibition, which runs from December 3-6 in Berlin, Germany.