Hyundai Motor Group’s Kia Motors has revealed details of a new eight-speed automatic transmission engineered for front-wheel drive vehicles.
The transmission was developed in-house and engineered to offer a high level of mechanical efficiency and smooth gearshifts. Even better, it occupies the same space as a conventional six-speed automatic transmission and weighs 3.5kg less.
Kia has already developed eight-speeders for rear-wheel drive but incorporating the same number of gears into a FWD model was more challenging due to packaging constraints and the need to mount the transmission transversely, competing with the engine, suspension and auxiliary components for space under the bonnet.
Intelligent packaging and 143 new patented technologies
Under development since 2012, the programme saw the automaker patent 143 new technologies to ensure a high level of performance and efficiency in a compact structure. This new transmission enables smooth acceleration from standstill, as well as greater fuel efficiency, improved NVH characteristics, and more decisive acceleration at high speeds than an automatic transmission with fewer gears.
To improve fuel economy, engineers significantly reduced the size of the oil pump (the main source of power loss in an automatic transmission) and simplified the structure of the valve body. Boasting the smallest oil pump of any production transmission in its class, the 8AT is able to use hydraulic oil more efficiently, distributing it evenly throughout the unit at all times.
Development teams also incorporated a direct control valve body to allow solenoid control of the clutch directly, rather than via several control valves. This enabled Kia to reduce the number of control valves from 20 to 12, resulting in quicker gear shifts, a more direct mechanical link to the engine and improved packaging.
Incorporating an additional clutch and gear over Kia’s existing 6AT, the ratio between the top gear and the lowest gear in the new transmission has been increased by 34% over the 6AT, resulting in greater fuel economy and improved NVH in higher gears and faster acceleration and climbing performance in low gears.
Debut in redesigned 2017 Cadenza
The front-wheel drive 8AT is making its global debut in the redesigned 2017 Cadenza – already on sale in some markets this year – and is standard on models with the 3.3-litre V6 petrol GDI (direct injection) engine.
In future, the new transmission will also be used in several mid-sized and larger front-wheel drive models, and, Kia said, “will serve as a stepping stone to the development of future advanced transmissions”.
Video: technical details explained
