Test drive Nissan GT-R: the history of a unique dual transmission
Nissan GT-R's all-wheel drive system is a technological masterpiece
The Skyline GT-R is an iconic name in Nissan's history, but it was the R32 generation that contributed the most to give the model a special aura. The following generations of the R33 and R34 developed it and made it an icon among sports car enthusiasts due to its unique character, exceptional road holding and reliability. But the pressure on the image is great. That's why when Nissan designers began developing the latest Skyline GT-R, a few years into the new millennium, they were challenged to create something as unique as road performance. Of course, previous models have left an indelible mark, and unchanged for them, the dual transmission by assumption remains in the new one. But this time the task is more difficult. In addition to all-wheel drive, a car with ideal weight distribution must be created, and its name will be reduced to only GT-R. Simple, clear and very convincing.
Like its predecessors, its all-wheel drive system will be called ATTESA (Advanced Total Traction Engineerig System for All Terrain). An expression of equally iconic technology developed over the years underpins the previous Skyline GT-R, but in the GT-R it will take on a whole new dimension.
Advanced technology back in 1989
The first mechanical form of ATTESA was developed for transverse engine vehicles and was introduced in the Bluebird for the Japanese market in 1987. A nearly identical system was later used in the GT-R Pulsar, the next generation Bluebird (HNU13) and the Primera. The original version used a viscometer-locked center differential, but was later replaced by a direct bevel gear connection and a viscometer on the rear axle.
However, much more interesting for the purposes of our story are the ATTESA E-TS (Electronic Torque Split) versions for Nissan sports cars with a longitudinal layout and an engine in the front. It was first used in the Nissan Skyline GT-R and Skyline GTS4. It is this system that makes the R32 generation Skyline GT-R one of the greatest cars of its time. Because Porsche In the PSK for the 959, Nissan designers use an electronically controlled multi-plate clutch that is driven by a hydraulic pump and directs some of the torque to the front axle.
This is an extremely advanced solution for its time, because no company at the time offered complete plate clutch units like today's BorgWarner or Haldex products. In principle, the rear axle is driven by a torque that is directed to it from the rear of the transmission via a propeller shaft. The transmission has an integrated transmission with an integrated clutch, from which the torque is transmitted to the front axle using another PTO shaft. The propeller shaft runs past the crankcase and is a common aluminum block, and the right axle shaft is shorter because the differential is on the right side. The system is controlled by a 16-bit computer that monitors vehicle movements 10 times per second.
Nissan's system is simpler than that of Porsche because the clutches are driven by a single hydraulic circuit and are not individually adjustable. It is this modular solution that underlies today's installations of this type and is cheaper, lighter and more compact.
What is interesting here is that the connectors in this case do not work constantly, as in most modern systems. Under normal driving conditions, the Skyline GT-R is rear-wheel drive, but during heavy acceleration or dynamic cornering, when more traction is required, the clutch kit is activated to direct some of the torque to the front axle. The proportion and moment of activation are monitored by the computer after analyzing parameters such as lateral acceleration, pressure in the turbocharger, throttle position and speed of each wheel, measured by the ABS sensors.
While the Nissan Skyline GT-R does not boast the ability to consistently distribute torque like the Porsche 959, it sits at the center of a historic rivalry between the powerful models of the two brands. The Skyline GT-R is much cheaper than the 959, but has excellent performance thanks to repeated tests at the Nürburgring. This mode of operation also has its positive qualities, as it maintains the vehicle's dynamic qualities without compromising the handling feel of the rear-wheel-drive model combined with greater cornering dynamics. Thus, the model manages to combine the best of both worlds and lay the foundations of the iconic Skyline GT-R image. In fact, the Porsche 959 has never received such a rating for handling.
An interesting feature of the system is the setting in which the more dynamically the driver drives the car, the less the front axle is activated. The Skyline GT-R is renowned for its door-first capability as a powerful rear-wheel drive model. The latter is not typical for vehicles with dual transmissions.
The next generation R33 Skyline GT-R evolved into the ATTESA E-TS Pro. Added to the rear axle is an electronically locked differential with two sets of clutches, new devices, materials and electronic controls. The same design will be developed in the R34 to reach its peak in the R35 powertrain layout.
One of a kind - GT-R with dual transmission and gearbox.
However, as we already mentioned, the name ATTESA (Advanced Total Traction Engineerig System for All Terrain) appeared a long time ago, like the system of the new GT-R. However, this does not mean that he is not unique in its kind.
In 2004, after much consideration, the designers decided that the new GT-R should use a six-speed dual-clutch transmission, a step into a whole new field because previous models had the engine and transmission in the front. In the name of rearward weight transfer, the inline six-cylinder engine is inherited from the new turbocharged engine with V6 architecture, and the transmission must be located on the rear axle in accordance with the so-called transmission layout and be of the DSG type. To do this, engineers turn to BorgWarner specialists for help, who in turn are partners with transmission supplier Aichi. Nissan's ambition is to build a car that rivals the best lap times on circuits like the Nürburgring. As we already mentioned, so the 486 hp super coupe. To be accurate in track control, the weight balance should be 50:50. In addition, the transmission must have a quick shift function. Since this solution will not be used in any other model of the company, it is clear that the transmission will have to be created and installed only in the Nissan GT-R. For the same reason, it was decided that it should be of only one type, as we have already said, with two connectors. What happens next is a true expression of fruitful cooperation. The transmission was developed by BorgWarner with special input from Nissan and Aichi engineers based at the company's Auburn Hills technical center in the US. Aichi designs the gears, while BorgWarner, who has an exceptional level of expertise and created the Bugatti Veyron drivetrain, handles the specific design, layout, etc.
In the first prototypes, the transmission was still located directly behind the engine. However, the project then entered the second phase when it was decided that the transmission would be located on the rear differential. For this, a structure has been created that should connect the transmission to the engine shaft, a multi-plate clutch is installed at the back, and then a mechanism that, using the propeller shaft, should transmit power to the front axle. The two transmission clutches are of the type used to lock up planetary automatic transmissions, but the friction materials are specifically designed for the GT-R's needs. The switching mechanism is also specific, provides an extremely fast response, and everything is controlled by a common control module. A special aluminum case was created, despite the desire for an even lighter magnesium, because the latter could not handle the load.
As we said, the all-wheel drive system is called ATTESA E-TS (Advanced Total Traction Engineerig System for All Terrain with Electronic Split). The name "all-terrain vehicle" should not mislead you, because it is an evolution of the names of the previous systems. It has priority over the rear axle, that is, the latter can receive from 100 to 50% of the torque. This, in turn, means that the torque is directed to it and with the specially developed GKN multi-plate clutch it can be directed forward from zero to 50%.
Torque is transmitted from the engine to the transmission through a carbon fiber reinforced polymer main shaft (main slow medium). The gear ratio is regulated by an electromagnetic multi-plate clutch. During acceleration, the torque ratio is approximately 50:50, while driving on the highway, almost all the torque is directed to the rear axle. When the vehicle's sensors detect a tendency to skid or understeer, most of the torque is absorbed by the rear axle, while with a tendency to oversteer, up to 50 percent of the torque is absorbed by the front axle. Its differential is open, and the rear (also GKN) has a multi-disc lock (LSD), which is activated when the traction of any of the wheels is reduced.
Despite the fact that the GT-R has evolved significantly in the eight years since its inception, the power of the six-cylinder unit has gradually increased from the original 486 to 570 hp, and the torque reached 637 Nm, the unique powerplant architecture has remained and continues to be. at the heart of the incredible behavior and dynamic qualities of this car.
Text: Georgy Kolev
