The
Nissan GT-R is the oddest vehicle in the supercar kingdom. Just looking at its specs on paper you wouldn't believe this car is as fast as
Nissan (and other independent verifiers) are saying. There is simply no way for it to be that much faster than a
Porsche 911 Turbo S – currently its closest competitor as far as performance goes - on the
Nordschleife and most other international racing tracks, right?
Both cars have 530 horsepower, are all-wheel drive, have
twin-turbocharged six-cylinder engines and sport twin-clutch gearboxes.
But that is where the similarities end, because by taking a peek at the
details it becomes clear the
Porsche should be a clear winner in almost all comparisons. Except... it isn't.
The BorgWarner double-clutch transmission in the GT-R
shifts gears in 200 milliseconds, almost as much as a torque-converter automatic, while the PDK gearbox in the Turbo S does it in just
8 milliseconds. Also, in almost every conceivable acceleration test the GT-R is slower than the Porsche, starting with the
3.5 versus the
3.3 seconds from naught to 100 km/h (62 mph) official figures. Last but not least, the current Nissan GT-R weighs approximately
150 kg (330 lbs) more than the 911 Turbo S.
So, what kind of pact with the devil have
Nissan
engineers made for the GT-R to completely obliterate cars that cost
twice or three times as much? Well, some may call it the devil, while
others may call it
ATTESA E-TS.
An acronym for
Advanced
Total
Traction
Engineering
System for
All-terrain with
Electronic
Torque
Split, the
ATTESA E-TS all-wheel drive system is not exact a novelty for
Nissan or Infiniti. The version, customized for the Nissan GT-R however,
is. To put it into perspective, this is the first and so far the only
rear transaxle-based all-wheel drive system for a front engined car.
During a standing start, the system sends only
2% of the available torque to the front wheels and
98%
to the rear, essentially making the GT-R a rear-wheel drive car. Thanks
to the amount of sensors, clutches and UFO technology Nissan has
invested in it, front and rear torque split can change in milliseconds
to a maximum of
50:50.
Unlike most conventional all-wheel drive systems and given the
transmission's transaxle positioning, the GT-R ATTESA E-TS uses two
almost parallel driveshafts, with a second driveshaft running slightly
to the right of the main driveshaft and engine sending power exclusively
to the front wheels through an open differential.
The other driveshaft, or better yet, the main one, goes from the engine
to the rear-based gearbox, from where it sends power through a limited
slip differential to the rear wheels, therefore varying the left/right
torque split at the rear axle. Integrated into the double-clutch gearbox
there's a transfer case in which, instead of a center differential lies
a center wet multi-plate clutch system. Coincidentally (or not), a
similar but obviously less advanced system was used by Porsche in the
959 supercar.
If you think the system is mechanically complicated, wait till you hear
about the electronics part. Since the GT-R can mechanically vary the
left/right torque split just at the rear axle (thanks to the
aforementioned active LSD), the ATTESA E-TS system takes care of that
also by sporting a computer controlled array of sensors.
This way, when the ABS sensors pick up that one of the front wheels is
spinning too fast compared to the other it is automatically braked, thus
mimicking a mechanical limited slip differential. Speaking of sensors
and computers, the ATTESA E-TS has its own ECU, which uses information
gathered from four ABS sensors, a three-axis G sensor, gearbox and
engine ECU sensors to control power in real time to each and every
wheel, depending on the driving conditions.
Translated into real life performance, this means that the GT-R's all-wheel drive system is pro-active, just like
BMW's xDrive.
For example, when entering a corner with full braking power, the
transmission ECU will perform an action mimicking an engine brake, while
with the help of the sensors the ATTESA E-TS ECU will continuously vary
the power sent to each wheel up to a
50:50 torque split in real time.
Since all the sensors present on the car are updated thousand of times
per second and most of the moving parts of the all-wheel drive system
are made out of light materials (for example, the driveshafts are from
carbon fiber), the ATTESA E-TS is literally a game changer on a car with
the GT-R's credentials. Now, imagine if the car was as light as the
Porsche 911 Turbo S and its gearbox changed speeds in the same amount of
time as the PDK...
Via: autoevolution.com
