ATTESA

ATTESA (acronym for Advanced Total Traction Engineering System for All-Terrain) is a four-wheel drive system used in some automobiles produced by the Japanese automaker Nissan, including some models under its luxury marque Infiniti.

The 'mechanical' ATTESA system was developed for transverse layout vehicles and introduced with the RNU12 Bluebird in the Japanese market, entering production in September 1987. The system ran right throughout the U12 series (RNU12/HNU12) and was fitted to numerous U12 models with differing engine and transmission combinations. An almost identical system is fitted to the RNN14 GTi-R Pulsar and the HNU13 Bluebird and the HNP10 Primera, finding usage in numerous other Nissan models.

Quite similar to offerings from other manufacturers, drive passes from the gearbox to a center viscous limited slip differential, into a transfer case splitting drive to a co-located front differential, and tail shaft connected to the vehicle's rear differential.

In the new system, as with a normal FWD car, the transmission contains a differential that drives the front wheels. However, an extra shaft from this differential also drives a bevel gear housed in the transfer case that permanently turns a driveshaft for the rear wheels (i.e. there is no longer a "center" differential). Housed in the rear differential is a viscous coupling that in normal conditions is disengaged. This means that for general driving, the system is FWD only. When the computer detects slippage of the front wheels, the viscous coupling engages and transfers up to 50% of the torque to the rear wheels. This system is superior in some aspects as there is less energy loss due to the normal FWD operation, however it is no longer a full-time 4WD system.

The Electronic Torque Split version of this all-wheel drive architecture is a more advanced system developed for Nissan vehicles with a longitudinal drive train layout. It was first used in August 1989 in the R32 Nissan Skyline GT-R and Nissan Skyline GTS4. Although the Skyline GT-R is exclusively AWD with manual transmission, ATTESA E-TS is also used in Nissan models that are available as rear wheel drive (RWD) with automatic transmissions fitted, such as the A31 Nissan Cefiro which was the second Nissan to feature the system exactly a year later in August 1990, and vehicles based on the Nissan FM platform (which are sold in certain markets under the Infiniti luxury brand).

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Wikipedia