Back in 1972 in Japan, Fuji Heavy Industries and its Subaru car brand launched their first passenger vehicle equipped with all-wheel drive. Little did they know that four decades later, the system employed by the Leone Estate Van 4WD would largely define the brand and the majority of its models.
All-wheel drive back then was a rudimentary technology. But even so, it was highly effective in providing much needed traction in a variety of environments and climates. Together with Subaru’s now-iconic flat-type engines, all-wheel drive dramatically improved grip in performance situations as well.
Fast forward 40 years and some 11.8 million (11,782,812 units as of January 31,2012, to be precise) all-wheel drive-equipped Subarus have rolled off its many production lines around the globe. Naturally, the drivetrain has evolved over the years and is now called Symmetrical All-Wheel Drive.
Nearly every vehicle (minus some JDM-spec kei-cars, trucks, and the rear-wheel drive BRZ) employs one of four basic variations of S-AWD. Throughout the decades, we’ve learned to love them all, and for that, we say Happy Birthday to Subaru’s effective all-wheel drive.
Here’s a brief breakdown of Subaru’s most current AWD setups:
- VTD-AWD or Variable Torque Distribution All-Wheel Drive
Meant for “sporty” vehicles, this setup utilizes a center differential that’s married to an electronically-controlled hydraulic multi-clutch limited-slip differential. In normal conditions, torque is split 45/55-percent front/rear, but can vary to 50/50.
- Active Torque Split All-Wheel Drive
Meant for models that emphasis fuel economy rather than performance, this front-wheel drive biased setup electronically controls a Multi-Plate Transfer case (MP-T) to vary torque in real time. In normal conditions, torque is split 60/40.
- Viscous Center Differential All-Wheel Drive
Meant for models equipped with manual gearboxes, the setup employs a torque-sensitive bevel gear-type center differential and viscous limited-slip differential. Normally, torque gets distributed at an even 50/50 split, but can react quickly to changing grip levels and manage slip accordingly.
- Multi-Mode Driver’s Control Center Differential (DCCD)
Meant for serious performance rides (i.e. STI models), the configuration combines a mechanical torque-sensing mechanical limited-slip differential and an electronically-controlled limited-slip differential. Mixing the two allows for near instantaneous torque and power distribution (thanks to the mechanical LSD) and a wider range of predictable behavior (thanks to the electronic LSD and its pre-programmed Gravel, Tarmac, and Snow modes). Normal driving means torque is distributed at a rear-biased 41/59 level.
Subaru will have a celebratory display at next month’s Geneva Motor Show in Switzerland, so stay tuned for more S-AWD goodness.
This info and more can be found at: http://wot.motortrend.com
