Voith Turbo, the German transmissions specialist, is launching a brand new four-speed automatic gearbox specifically designed for the bus market at EuroBus Expo 2012 in November.
The new Euro 6 compliant gearbox, DIWA.6, will reduce noise emissions, provide better thermal stability, and will improve efficiency. It has been designed for double-deckers, single-deckers, and the midi-bus sector.
The design changes to previous models include modifications to the gear pump, heat exchanger, converter pump, working pressure valve, acoustics and housing, and stop-start preparation. The new planetary carrier is lighter but maintains the same strength as previous models
“The reduced weight of DIWA.6 will contribute to improved fuel efficiency of between three and five per cent,” said John Domigan, Voith Turbo’s sales and marketing manager.
“The new gearbox has a number of additional benefits. For example, the operating pressure automatically adjusts to the output required during the stop-start cycle of a bus so that pressure can be reduced whenever possible.”
He went on: “In addition, when the vehicle is stationary the automatic shift into neutral separates both the transmission mechanics and the converter from the engine. This allows minimum fuel consumption.
“Another benefit is that sensors detect if the vehicle is rolling back during starting and ensure the bus stays in neutral for as long as possible. The result is that the engine doesn’t have to work against the active brake using up unnecessary fuel.”
In the UK Voith Turbo transmissions have been supplied to the double-decker and single-decker sectors for several years. Their gearboxes are in about 7,000 buses manufactured by Dennis, VDL, Man and Volvo.
Two years ago Voith Turbo entered the midi-bus sector and has become the sole supplier to Wrightbus as well as enjoying considerable success with Stagecoach. About 500 transmissions have been sold in the sector.
Worldwide DIWA gearboxes are fitted to 150,000 buses. The DIWA system comes from Differential Wandler – German for differential torque converter that incorporates a retarder.
The DIWA’s first gear replaces the first two gears on a conventional automatic transmission cutting fuel consumption. It reduces gear shifts at lower speeds giving a more comfortable ride for passengers.
John Domigan said that the new DIWA.6 has undergone thousands of miles of proving in trials with different manufacturers’ buses throughout Europe, including the UK.
“Our transmissions, unlike our competitors’, are made specifically for the stop-start cycle of buses,” said John. “Our products are sold on reliability and longevity and we believe there is now a growing awareness in the UK market that price is not the only important criteria.”
“We are extremely optimistic that whole life costs are forming a more crucial part of the purchasing decision, and that the longevity of our products – which are at least seven or eight years, and longer in some cases – gives us a competitive advantage.”