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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 gearbox 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 centre viscous limited slip differential, into a transfer case splitting drive to a co-located front differential, and tail shaft connected to the vehicles rear differential.
2000+ ATTESA Update
In the new system, as with a normal FWD car, the gearbox 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 the driveshaft (i.e. there is no longer a "centre" 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 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 ATTESA 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 and manual, ATTESA-ETS is also used in Nissan models that are also available as RWD and also 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).
The ATTESA-ETS version uses a mostly conventional RWD gearbox. Drive to the rear wheels is constant via a tailshaft and rear differential, but drive to the front wheels is more complex by utilizing a transfer case on the rear of the gearbox.
The drive for the front wheels comes from a transfer case bolted on the end of an almost traditional Nissan RWD transmission although the tail-shaft is different to couple to the transfer case. A short driveshaft for the front wheels exits the transfer case on the right side. Inside the transfer case a multi-row chain drives a multi-plate wet clutch pack. Drive from the chain is apportioned using this clutch pack in the transfer case "differential" (the system thus does not involve a regular gear differential as in a full-time 4WD layout, but rather a center clutch), similar to the type employed in the Steyr-Daimler-Puch system in the Porsche 959. This unit is lubricated with its own dedicated NS-ATF oil supply (Nissan Special ATF) and is not in any way connected to the oil in the transmission. Some Nissan models have an external oil cooler with an electric oil pump to cool this oil.
Situated on top of the rear differential is a high pressure, low volume electric oil pump. This pump pressurizes Normal ATF oil (0-288psi) into the transfer case to engage the clutchpack. This oil only engages the clutchpack and does not mix with the NS-ATF lubricating the tranfercase. The higher the oil pressure the transfer case is supplied with from the pump, the more the clutch pack engages, enabling the torque to the front wheels to be varied. Exiting the transfer case, the front drive shaft runs along the right side of the transmission, into a differential located on the right of the engines sump. This is a cast aluminum unit, with the sump and front diff made as one joined unit that can not be separated. The front right axle is shorter than the left, as the differential is closer to the right wheel. The front left axle runs through the engine's sump to the left wheel. Video of ATTESA system components
To control the ATTESA-ETS system, there is a 16-bit microprocessor that monitors the cars movements at 10 times per second to sense traction loss by measuring the speed of each wheel via the ABS sensors. Also a three axis G-Sensor mounted underneath the center console feeds lateral and longitudinal inputs into an ECU, which controls both the ATTESA-ETS 4WD system and the ABS system. The ECU can then direct up to and including 50% of the power to the front wheels. When slip is detected on one of the rear wheels (a rear wheel turn 5% or more than the front wheels), the system directs torque to the front wheels which run a non LSD diff. Rather than locking the AWD in all the time or having a system that is "all or nothing", the ATTESA-ETS system can apportion different ratios of torque to the front wheels as it sees fit. This provides the driver with an AWD vehicle that performs like a rear wheel drive vehicle in perfect conditions and can recover control when conditions aren't as perfect.
From factory, the system is set up to provide slight oversteer in handling, and in fact the harder the car is cornered, the LESS the 4wd system engages the front wheels. This promotes the oversteer rather than understeer which is apparent in most AWD/4WD vehicles. The advantage to a more traditional ATTESA (Viscous LSD) system is response in hundredths of a second.
Some models fitted with the ATTESA-ETS system, such as the Nissan RS4 Stagea, have a "S" button on the dash. This will bypass the control system of the ATESSA-ETS ecu and lock the transfer case into full 4wd. This is to be uses at low speeds in snowy and icy conditions only as understeer is greatly increased in this mode.
In 1995, with the introduction of the R33 Skyline GT-R, Nissan introduced a new version of their ATTESA system. It was named ATTESA-ETS Pro, as an upgrade from the earlier ATTESA ETS. It was standard equipment in the R33 Skyline GT-R Vspec model, however it was offered as an option on the standard R33 Skyline GT-R, and called the "Active LSD option". It was also standard equipment on all R34 Skyline GT-R models. The active rear LSD was also available as an option on some rear wheel drive Nissans such as the R33 GTS25t and C34 RS Stagea.
ATTESA-E-TS Pro differs from the standard ATTESA-E-TS in a few ways. Where ATTESA-E-TS controls the front to rear torque-split, the Pro is also capable of left-and-right torque split to the rear wheels. This is done via an active rear limited-slip differential. Additionally, ATTESA-E-TS Pro was marketed as controlling the ABS system to each wheel independently, where as the previous ABS ECU could sense the speed of each wheel it's ABS pump is only 3 channel, with both back brakes linked as one unit. Although this is not part of the AWD system, but the ECU makes use of the same sensors to determine wheel slip and traction.
On ATTESA-E-TS Pro equipped vehicles, the front differential remains a standard differential, not being linked to the ATTESA-E-TS Pro system.
R33 updated wheel speed sensors 100 times a second R34 updated wheel speed sensors 1000 times a second.
ATTESA-ETS (GT-R version)
The 2009 Nissan GT-R uses an updated version of the ATTESA-E-TS, and is designed to work with the car's rear transaxle layout. The system is unique in the way that it utilizes two driveshafts under the vehicle's centerline, with a second driveshaft running slightly to the right of the main driveshaft and engine sending power to the front wheels. It is so far, the only rear transaxle-based AWD system for a front engined car in production.
Unlike the previous ATTESA systems which relied heavily on mechanical feedback, the system in the GT-R uses electronic sensors and hydraulically-actuated clutches. It also has a yaw-rate feedback control system, effectively managing slip angle. Front rear torque split can go from 2:98 during a standing start to a maximum of 50:50
Models and ATTESA type
|Nissan Model||Year Released||ATTESA type|
|[Infiniti QX4] | 1997-2003 ATTESA E-TS system is used in the following models:
- R32 and R33 (1989-1997) GTS4 Skyline
- GT-R - 1989–2003
- Nissan Stagea
- A31 Cefiro
- Infiniti G35x/G37x/Nissan Skyline (V35 & V36)
- Infiniti M35x/45x/37x/56x/Nissan Fuga
- Infiniti FX
- Infiniti EX/Nissan Skyline Crossover (with Active Brake Limited Split for side-to-side torque split, as needed)
- Nissan Cedric (Gloria\Cedric with RB25DET engine)
ATTESA E-TS Pro system is used in the following models:
- R33 (1995-1997) Nissan Skyline GT-R (offered as a factory option)
- R33 Nissan Skyline GT-R V-spec
- R34 (1998-2002) Nissan Skyline GT-R (all models)
ATTESA E-TS Pro (GT-R version) is used in the following model(s).
- 2008+ Nissan GT-R
- 4Matic - a four-wheel drive system from Mercedes-Benz
- 4motion - a four-wheel drive system from Volkswagen
- All-Trac - a four-wheel drive system from Toyota
- Nissan Bluebird
- Nissan Pulsar
- Nissan Skyline
- Nissan Skyline GT-R
- Quattro (four wheel drive system) - a four-wheel drive system from Audi
- S-AWC - a torque vectoring four-wheel drive system from Mitsubishi Motors
- SH-AWD - a four-wheel drive system from Honda