War of the New Generation Sports AWD systems

[hightower99]

Well It looks like the war will be here soon. A three way battle between the latest generations of Sports AWD systems is about to commence as their respective cars are being released onto the world.

I am talking about the battle between Mitsubishi, Nissan, and Subaru. Argueably they are the top three when it comes to sports AWD systems. Mitsubishi with the now old ACD, and AYC systems, which are now being replaced by the brand new S-AWC system on the new EVO X. Nissan coming out with the new version of it's ATTESA-ETS Pro system on the new Skyline GT-R. Finally Subaru with the brilliant Symmetrical AWD and DCCD systems on the new WRX STi.


Nissan System:
ATTESA-ETS (acronym for Advanced Total Traction Engineering System for All - Electronic Torque Split) ATTESA-ETS Pro.
The ATTESA-ETS layout is advanced and uses a 16bit microprocessor that monitors the cars movements at 100 times per second to sense traction loss. Two G-Sensors mounted underneath the centre console feed lateral and longitudinal inputs into an ECU. The ECU can then direct up to and including 50% of the power to the front wheels. When slip is detected on a wheel, the system directs the torque away from that wheel to one that has traction. Torque is apportioned using a clutch pack center differential, similar to the type employed in the Steyr-Daimler-Puch system in the Porsche 959. This series of clutch packs is contained within the 'transfer case,' which is mounted to the rear of the gearbox.
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 different 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. The advantage over a more traditional ATTESA (Viscous LSD) system is response time in only a few hundredths of a second.
ATTESA-ETS Pro
ATESA-ETS Pro differs from the standard ATTESA-ETS in a few ways. Where ATTESA-ETS controls the front to rear torque-split, the Pro is also capable of left-and-right torque split for the rear wheels. This is done via an active rear limited-slip differential. Additionally, the ATTESA-ETS Pro was marketed as controlling the four-wheel independent ABS braking system. 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-ETS Pro equipped vehicles, the front differential remains a standard limited slip differential.

Mitsubishi System:

ACD Active Center Differential

The ACD system makes it possible to control the flow of power through a limited-slip differential, going from a non-drive state to a direct drive 4WD state via a center differential limited-slip mechanism (internal transfer) that electronically controls a hydraulic multiple-disc clutch.
During acceleration or deceleration, ride stability increases as one approaches the direct drive 4WD state. Improved cornering performance is the result as the power to the limited slip-differential approaches the non-drive state.
Three optimal modes can also be selected to match road surface conditions.


Super Active Yaw Control
The Super AYC system controls the vehicle's rotational forces (yaw moment) by sensing road surface conditions, steering wheel angle, lateral acceleration, and electronically controlling the distribution of power to the left and right rear tires.
When entering a curve, the power is applied to the outer wheels thereby improving maneuverability. When accelerating in the latter half of a curve, the power is transferred back to the outer wheels and reduces understeer. In addition, power is transferred from the wheel(s), regardless of side, on slippery or rough surfaces to the wheel(s) that are on a non-slip surface. This improves both stability and acceleration from a standstill.

ACD & AYC are equipped on the Lancer Evolution VIII.


The Sports ABS system supports braking when entering into a corner by controlling power to all tires depending on handling characteristics.
Braking can be controlled to obtain optimal damping at each tire based on information from 4 wheel speed sensors and steering wheel angle sensor.

The new EVO X will include upgraded versions of ACD and Super AYC as well as the Sports ABS (which isn’t on EVOs yet) to create a total system they call S-AWC (Super All Wheel Control)


Subaru System:

The Driver Control Center Differential (DCCD) Symmetrical All-Wheel Drive system uses a planetary-type center differential to provide a 41:59 torque split, with automatic and manual differential modes.
Center differential lock-up is controlled by both a mechanical limited-slip type differential and an electronically controlled limited-slip differential. The mechanical limited-slip differential activates and operates initially in response to changes in engine torque, improving overall vehicle stability when accelerating or decelerating. In automatic mode, the electronic limited-slip differential controls the differential lock-up by evaluating the amount of lock-up in the mechanical limited-slip. The total amount of lock-up is based on the combination of both differentials. A steering sensor input improves torque transfer response by more accurately relaying the car’s cornering situation.
Set in automatic mode, the DCCD system can vary the torque distribution ratio as needed in response to vehicle acceleration, deceleration, steering angle, cornering force and wheel slippage.
In manual mode, DCCD allows the driver to select center differential lock-up to optimize All-Wheel Drive performance for varying driving conditions. The driver first selects manual mode with a console-mounted button and then turns a thumbwheel on the center console to select from among six levels of lock-up. Increasing the locking factor keeps more power at the front wheels (max. 50:50 torque split with 100 percent lock-up selected), which the driver might want in certain driving conditions or on particular road surfaces.
A helical-type limited-slip front differential and Torsen® limited-slip rear differential help to optimize power distribution side-to-side, helping to prevent the inside wheels from slipping during cornering. This system also includes a TCS (traction Control System) VDC (Vehicle Dynamics Control).


So who likes what and why?

Any actual driving experiances (good or otherwise)...

And finally what do you think (technology wise) is next in the war of sports AWD?

[kingofthering]

hmmm.... don't neglect quattro. It really depends on your driving style.

[Ferrer]

Originally Posted by kingofthering

hmmm.... don't neglect quattro.

And Alfa Romeo's new Q4 Torsen system.

[blingbling]

I don't think any of us knows enough of the exact technicalities to know which one is the best? There are jsut too many things we don't know.

Are they used to their maximum potential? Did they want to obtain different objectives (safety/performance/efficiency/etc...)? How flexible and versatyle these system are? How reliable and consistent are they?There are just too many questions.

[kingofthering]

I like the mechanical ones. Nissan's is basically computers. Too scary.

[johnnyperl]

Originally Posted by hightower99

So who likes what and why?
Any actual driving experiances (good or otherwise)...

Two of the systems haven't even been released!

[h00t_h00t]

With traction control and ESP so advanced they can make a 500hp Mercedes Super Barge feel normal and boring, why not just go RWD?

[2ndclasscitizen]

None of those are new. ATTESA has been around since the R32 GTR (so '89 IIRC) with the ETS Pro version being on the V-Spec R34s so about 99 or 2000. S-AYC and ACD have been around since the Evo 7, and the DCCD has been around since the 22B but has only been on JDM vehicles until recently (the MY05 here)

[092326001]

i like quattro

[lightweight]

The Nissan is by far the most user friendly.
The Subaru and Mitsubishi need more experienced drivers.
Anyone know when Honda is releasing its AWD?

[Egg Nog]

It's amazing how far ahead of its time the Porsche 959 was.

[Niko_Fx]

Originally Posted by 092326001

i like quattro

Why exactly?

[2ndclasscitizen]

Originally Posted by lightweight

Anyone know when Honda is releasing its AWD?

They already have. It's available in the new Legend which is reported to be a very good drive

[Quiggs]

Originally Posted by Niko_Fx

Why exactly?

I <3 Quattro because it can climb walls. That's how much grip it has.

<insert video of RS4 climbing ski slope here>

[kingofthering]

http://youtube.com/watch?v=nPTPD-xUO...elated&search=