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Voith Turbo launching new 4-speed gearbox for bus market; improved fuel efficiency of 3–5% via reduced weight

Voith Turbo, the German transmissions specialist, is launching a 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.

DIWA.6 transmission. Click to enlarge.

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. 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.

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.

— John Domigan, Voith Turbo’s sales and marketing manager

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.


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