The combination of an intelligent shifting program and a fuel-saving automatic transmission can prove more economical in city bus operation than hybrid technology, claims German transmissions specialist ZF.

“Standard hybrid drives are often based on outdated technology," said Wolfgang Schilha, senior vice president of the ZF Bus Driveline Technology business unit of Germany’s ZF Friedrichshafen.

A new intelligent shift program, TopoDyn, was key to the economy gains of the Ecomat transmission, said Schilha. TopoDyn is able to pre-program the transmission with the
various routes the bus may be taking and is able to ensure the engine always operates
in its most efficient mode.

 

Tests on a fleet of buses in Chicago showed an 18 percent reduction in consumption compared to similar vehicles with standard powershift transmissions, said ZF; even when compared with currently available hybrid transmissions the Ecomat-TopoDyn pairing used seven percent less fuel, according to ZF.

In a further trial ZF’s six-speed EcoLife automatic transmission, pre-programmed with TopoDyn, has been fitted to a giant 19-meter (60 ft) Mercedes-Benz CapaCity articulated bus in Stuttgart’s city fleet. Stuttgart is a hilly city, with over 300 meters (975 ft) elevation difference along its bus routes. Considerable CO2 and fuel savings have resulted, says ZF.