Less fuel consumption and noise emissions, more comfort and performance, and suitable for a wide torque range: The ZF EcoLife 6-speed automatic transmission is a real all-rounder. That there is more to it is proven once again by ZF at this year's Busworld Kortrijk. The innovative start/stop function, that reduces fuel consumption in urban applications by up to 10 percent, as well as the new EcoLife Coach transmission variant, that excels with an input torque of up to 2 300 Nm for intercity buses and coaches, will have their premieres there.
City buses often have to face stop-and-go traffic, have to wait frequently in front of traffic lights or road obstacles like construction sites, and are stopping at many bus stops compared to the covered distance. For this reason, ZF developed a start/stop function especially for this means of transport and for its EcoLife automatic transmission in particular: This function is the main prerequisite for automatically switching off the engine when the vehicle is at a standstill - and also for re-activating it as soon as the driver changes from the brake to the accelerator pedal. This results in additional fuel savings of up to 10 percent. ZF is the first supplier that offers this technology for the high demands of city bus applications as well as for the most frequent engine torques of 1 000 to 1 600 Nm.
In the transmission, the engineers strengthened the converter and the lock-up clutch. In addition, there is an optional but completely integrated hydraulic solution for the extremely quick responsiveness. The up-to-date volume production transmission includes all of the design developments.
For the start/stop function it is essential that the transmission's shift elements are filled with oil even after a longer engine standstill as soon as the accelerator pedal is engaged - only then the vehicle is ready to set off. To ensure this, ZF did not have to develop and install an additional, external transmission oil accumulator for the EcoLife applications: The engineers just used the oil accumulator of the ZF primary retarder integrated into the transmission.
EcoLife Coach for demanding tours
ZF EcoLife is the worldwide benchmark for automatic bus transmissions used in the most demanding application area - the city traffic. Based on this, the technology company now extends the transmission family by the EcoLife Coach version. It was specifically designed for the application in intercity buses and coaches and for particularly demanding routes. The torque converter as most important new development transmits input torques of up to 2 300 Nm - and thus the comparably high performance of coach engines - without difficulty.
In mountain regions, for instance, intercity buses and coaches must frequently brake hard due to many and often narrow bends and must then accelerate strongly again. For this reason, many gear changes in a short period of time are required - just as in city traffic. This is where ZF's EcoLife Coach benefits from its high efficiency and its smooth and efficient acceleration without tractive force interruption when changing gears. Speed and drive are not reduced which has a positive effect on both fuel consumption and noise emissions. Furthermore, buses with ZF EcoLife Coach are easy to maneuver and enable very slow driving without clutch wear.
When driving downhill, ZF's primary retarder pays off: This system is the only one that develops its braking effect depending on the engine speed and not, as conventional secondary retarders do, in relation to the vehicle velocity. Thus, the retarder also efficiently decelerates on long downhill routes and at low bus velocities increasing safety and reducing the wear of the service brakes.
A current trend gives further reasons why to opt for EcoLife Coach: Many coaches also drive often in cities a long time. For instance when they are used as shuttles between city hotels and the airport or for sightseeing at the destination. In both cases, the buses and their transmissions have to tackle both low speeds and frequent gear changes in stop-and-go traffic.