8-speed-automatic transmission by ZF
ZF has developed a new automatic car transmission with eight speeds that can achieve 11% fuel savings. The priority aim in development, however, was not the maximum number of gears, but minimum consumption.
Fuel saving and minimizing CO2 emissions
Several innovations have been introduced in the new 8HP to reduce fuel consumption: the completely new transmission concept with four gear sets and only two shift elements open, a higher overall gear ratio, a variable oil pump, new torque converter, and optimized hydraulic and transmission control. Also available as an optional add-on is a stop/start function that automatically cuts out the engine when the vehicle stops and restarts it when the brake is released.
The start/stop function is enabled by the development of the hydraulic impulse oil storage (HIS). It supplies the hydraulic oil that the transmission's shift elements need for starting. When the engine is switched off, it allows for a quick start – as it is required with the start/stop function. Already 350 milliseconds after starting the engine, the vehicle is ready for setting off. With the start/stop function of the hydraulic impulse oil storage, it is possible to reduce fuel consumption by another 5%. Compared with the worldwide most efficient 6-speed automatic transmission by ZF, the newly developed 8-speed automatic transmission saves another 11%.
Faster acceleration
In addition to its positive effect on fuel consumption, the higher overall gear ratio improves the acceleration values of the ZF product. Shorter gear steps, particularly from first to second gear, give vehicles fitted with the 8HP faster acceleration and enable improved shift quality in the lower gears. Two additional gears also helped the ZF engineers achieve an increase in the overall gear ratio, without loading individual gears with excessive torque or speed. This harmonious torque and speed distribution is less harsh on parts and allows reliable operation with fewer "hefty" gear sets.
Precise gear shifting
200 milliseconds is how long the 8HP 8-speed automatic transmission takes to carry out a gear shift - fast and smooth. Even a professional driver can't shift as fast as this. This gives gear shifting that impressively combines driving pleasure, efficiency, and maximum comfort. Direct gear jumps over two or more gears - including the extreme of shifting from eighth to second - are also possible. In conjunction with the intelligent adaptive shift strategies, this guarantees maximum agility and driving fun.
TopA variable modular kit for future technologies
In a market environment likely to continue to be characterized by model pluralism, the new transmission series needs to be able to meet a wide range of different requirements. Right from the conception of the 8HP, attention was paid to ensuring its suitability as a modular kit for other starting and all-wheel concepts, without any changes to the basic transmission concept. The new 8-speed automatic transmission is also ideally designed for hybridizing the driveline: Up to 30% fuel savings can be expected from the full hybrid version in urban-cycle traffic.
8HP product benefits
The challenge is to leave something out and end up with more. At first glance, this value-added formula appears to be a contradiction. But a closer look shows that the facts speak for themselves. Overview of the 8-speed automatic transmission product benefits.
| New gear set concept | Only 5 shift elements with 4 gear sets, of which only 2 are open in each gear. 3 multi-disc clutches and 2 brakes, enabling a compact, highly efficient design. |
|---|---|
| Higher overall gear ratio | Overall gear ratio of 7.0. The transmission consistently adapts to the optimum engine operating range for improved acceleration and lower fuel consumption. |
| Higher power-to-weight ratio | Lightweight components combined with a revolutionary gear set concept: 2 additional gears transfer more torque with fewer components and unchanged weight characteristics. |
| Lower drag loss and greater efficiency | Only 5 shift elements with 4 gear sets, of which only 2 are open in each gear, and a new axially parallel vane cell pump increase the efficiency of the transmission. Energy losses are reduced to a minimum. |
