Symmetrical AWD

Unmatched Performance. You Own the Road.

INTRODUCTION

The development of our symmetrical full-time All-Wheel Drive system and other new technologies has been the driving force behind Subaru for many years now. The reason for our dedication is that we want to get back to the basics of building cars that more and more people can enjoy driving with complete confidence. These ideal cars reward their owners with superior all-around performance that follows the driver's commands perfectly. Subaru started producing four-wheel drive passenger vehicles in 1972. Since then, we've unveiled a series of technological advances, each improving and perfecting what has become known as the Subaru symmetrical full-time All-Wheel Drive system, which constantly adjusts torque distribution to front and rear wheels.

This single-minded approach to achieving perfection is what makes all Subaru cars perform so uniquely well on the road. It's not just about better handling in extreme conditions. It's about taking the whole driving experience to new levels. making life easier, safer and more enjoyable for every driver, in every situation. By understanding how this core technology directly affects the way you handle the road ahead, you'll be able to relate each component to the benefit it brings and feel more confident behind the wheel in the future.

Only from Subaru

The legendary Subaru symmetrical full-time AWD system is respected the world over.

The inherent superiority of symmetrical full-time AWD has been proven again and again in the unforgiving arena of the FIA World Rally Championship. In the heat of rally competition, the same cutting-edge technologies used in our road cars are tested in the toughest conditions, showing their true value and reinforcing their benefits.

A system for pure driving enjoyment.

Whether on the rally circuit or on the road, our philosophy is to translate the driver's every wish directly into action, with cars that drive, corner and stop exactly as the driver wants. Such complete control means a smoother driving experience, making full use of the inherent advantages of the Subaru symmetrical full-time AWD system. This system provides more than just an exhilarating on-road driving experience, it also provides the added benefits of truly exceptional all-weather safety.

Subaru and the pursuit of safety.

An exceptional driving experience and world-class active safety should go hand in hand. That's because stability is maintained right up to the limits of performance, which means you can drive with confidence in virtually any weather or on any road.

Confidence

The advantage of Subaru Symmetrical AWD.

Subaru has been convinced for decades that the ideal powertrain for delivering performance and safety is our legendary symmetrical full-time AWD system. Why not front- or rear-wheel drive? While both undoubtedly have their advantages in certain conditions, only power distributed to all four wheels can provide both an enjoyable driving experience and a greater feeling of security in all situations.

First, there's the radical combination of placing compact, horizontally-opposed SUBARU BOXER engines - which help to provide a low centre of gravity - and an efficient, balanced transmission along the centreline of the vehicle. That creates a stable foundation that translates into superb cornering and responsiveness.

With the symmetrical AWD system at its heart, the whole package is highly efficient, providing extremely precise steering response in corners as well as surefooted stability when travelling at high speeds or in bad weather. It is this level of balance and predictability that gives agility and responsiveness beyond the capabilities of conventional AWD systems. That's why Subaru has championed this technology for so long.

Our symmetrical full-time AWD system's balance is mainly due to its longitudinally mounted components, with almost total side-to-side symmetry. In this system, engines are mounted low, while heavy items (such as the transmission) are mounted further back, within the wheelbase. With this design, weight is balanced laterally and the centre of gravity is where it should be: low to the ground and between front and rear wheels.

Power

The advantages of a horizontally-opposed SUBARU BOXER engine.

Our horizontally-opposed SUBARU BOXER engines are what make the whole drivetrain layout possible. The key to this flat engine configuration is that its opposing pistons effectively balance out each other's vibrations. Compared with in-line or V-type engines, this gives smooth, seamless, fluent power delivery right through the rev range. Even more importantly, the design is shorter and shallower than other engines, which means it is compact, lightweight and very rigid. In turn, this lets us fit the engine down low in the chassis to provide a low centre of gravity. Both in-line and V-type engines have advantages and disadvantages - as you can see below, but the built-in benefits of the SUBARU BOXER engine have proved to Subaru - and Subaru owners - that this is the one true way to harness performance and ally it with remarkable drivability. Whatever the road, whatever the conditions, whatever the challenges, we firmly believe that this is the route to genuine all-around driving enjoyment.

Click here to view a Subaru Hoizontally-Opposed Engine diagram

Performance

Torque Distribution System.

Whether it's tackling a gravel-strewn FIA World Rally Championship special stage or simply running into standing water on tarmac, keeping your car stable by getting the best possible traction is vital. That's where the technology of our torque distribution system sets Subaru apart from conventional four-wheel drive set-ups. Created specifically for our symmetrical full-time AWD system, it actively distributes engine torque to individual wheels - not just to front or rear axles, as some others do. In fractions of a second, our smart torque distribution system automatically adjusts the amount of torque, giving maximum grip and stability wherever and whenever it's needed - not only in extreme conditions but also in everyday driving. The result is dynamic handling that feels truly intuitive, making the car behave like an extension of the driver's body and mind. Even when road conditions change unexpectedly, torque distribution plays a crucial role in achieving the goal of stability and control.

LSD (Limited-Slip Differential)

At the core of our legendary symmetrical-full-time AWD system is Subaru's centre limited-slip differential. A sophisticated mechanism controls torque distribution and limits tire slip proactively - rather than reactively - depending on the different surfaces you encounter along your journey. This real-time adjustment ensures that a Subaru always uses its AWD traction and stability to the fullest extent. However, it's not just for slippery and adverse conditions, as it also benefits handling on dry, pristine roads. So, while you may never see our centre differential, it's very reassuring to know that this marriage of technology and mechanical engineering is constantly working with all the other Subaru technologies to keep your car stable and you safe.

Physics

Driving Dexterity

When you're sweeping through a difficult bend or making a high-speed lane change to avoid an unexpected obstacle, you need to react quickly - without upsetting the car's behaviour. This is where a Subaru's natural agility and neutral handling characteristics help keep you safely on your intended course. They're born out of a combination of factors that make up our exceptionally balanced drivetrain.

First, there's the inherent agility of having a lightweight, horizontally-opposed SUBARU BOXER engine that is mounted low to the ground. Then, the main drivetrain components - like the transmission, transfer case, differential and propeller shaft - are mounted inside the wheelbase, which means that the weight distribution is ideally balanced between the front and rear of the car.

This means that there is no unnecessary weight overhanging the front or rear that could help to throw the car off its intended path during sudden manoeuvres. Since the layout is also symmetrical from left to right, Subaru vehicles corner with much more confidence and neutrality than vehicles with other types of drivetrain configurations.

Dynamics

A Balanced Body

Body control is the second way to achieve nimble, athletic performance when cornering - especially where changes of direction follow each other in quick succession (as illustrated below). Under these circumstances, Subaru's low centre of gravity complies much better with the laws of physics, instead of the driver trying to fight against them. Again, the horizontally-opposed SUBARU BOXER engine plays a major part in resolving this situation. The higher the centre of gravity, the easier it is to lose balance and control, because the vehicle tends to roll more through bends. With Subaru vehicles, it's a case of the lower the better - which is why there's such a dramatic difference between the two examples below. The body language of a Subaru is always composed and stable, making driving more comfortable, less tiring and ultimately, more enjoyable - which is exactly why Subaru makes cars the way it does.

Click here for a diagram that illustrates Suburu's low centre of gravity


Yaw Moment/Inertia

Whenever a car turns a corner, centrifugal force acts on the body to move it outwards. This motion is amplified when the centre of gravity is high, so the car takes longer to recover its equilibrium afterwards. This "pendulum effect" is well understood, which is another reason for relying on Subaru's symmetrical full-time All-Wheel Drive system. The amount of force generated is called yaw moment or inertia. When you move the weight of the pendulum closer to the centre of gravity like in a Subaru, the yaw moment is much smaller, which means the car is easier to turn, rolls less and is considerably more poised and stable.

Poise

Symmetrical AWD

When it comes to secure handling and stability in both everyday driving and adverse conditions, Subaru's symmetrical full-time AWD system will always have the edge over other ordinary four-wheel drive or all-wheel drive systems. With a Subaru, its instinctive, rally-proven capabilities inspire you to drive the car with confidence - even when travelling quickly over rough or slippery roads, where traction can be easily compromised. It all comes down to pure driving enjoyment no matter where your travels take you. In other manufacturers' systems, low traction levels usually activate some form of traction control system, which attempt to make up for the vehicle's inherent flaws. These traction control systems can lead to instability when cornering on wet or greasy surfaces, as a sudden loss of power can upset the vehicle's balance. At Subaru, we believe that the first line of defence should always be the tenacious grip and stability of symmetrical full-time AWD.


Subaru Vehicle Dynamics Control (VDC) system automatically uses the correct amount of torque, engine output and braking to individual wheels to prevent the car from skidding, thus helping you avoid obstacles while staying in full control of your vehicle.

Subaru Vehicle Dynamics Control system

No matter how great a vehicle's drivetrain or grip, we recognize that sometimes even the best of drivers find themselves in a situation that calls for a sudden or even violent change of direction to avoid an accident, that could possibly cause a spin. That is where Subaru Vehicle Dynamics Control (VDC)* system saves the day. In addition to the constant security of symmetrical full-time AWD, it acts as a second line of defence in emergencies, kicking in only when it's really needed. Sensors monitor vehicle speed, throttle opening, gear position, lateral G forces, yaw rate, brake status and steering wheel angle to analyze the actual driving situation. In the event of a loss of control, a computer simultaneously coordinates control of torque distribution, engine output and the Anti-Lock Braking System (ABS) to stop the car from spinning. VDC doesn't detract from the everyday pleasure of driving a Subaru, but even if it never betrays its presence, it's very reassuring to know it's there if needed. * Available on certain models.

Cornering

What is Traction

Only when tires are turning, and those palm-sized patches of rubber are gripping the road, can a car's torque make it go where the driver wants. Obviously, Subaru's symmetrical full-time AWD system is superior to front- or rear-wheel drive in transmitting more torque to the road. However, due to our advanced torque distribution system and the fact that the amount of torque transmitted to each wheel is being constantly adjusted in real time, it even outperforms other AWD systems. Better traction, grip and surer turning are yet another tribute to Subaru's superior technologies.

By comparison, two-wheel drive merely does what it says. Whether it's through the front or rear wheels, there are always two tires not getting any torque - so they have no part in governing the way power is used to control the car. On the other hand, Subaru's advanced symmetrical full-time AWD system brings together the best attributes of both systems without any of their compromises and is even better than ordinary four-wheel drive or AWD drivetrains. To fully capitalize on these strengths, the Subaru symmetrical full-time AWD system also utilizes sophisticated, rally-derived long-travel suspension to help maintain optimum tire-to-road contact at all times.

Symmetrical AWD

Outclassing ordinary four-wheel drive or all-wheel drive drivetrains, the Subaru symmetrical full-time AWD system delivers crisp turning, easy control and maximum stability, all in perfect balance. It's the ideal combination of the virtues of front- and rear-wheel drive in one, without any of their potential drawbacks.

FWD

Here, front wheels control power and steering, leaving the rears to simply support the body. Turning is stable, so control is easy, but less athletic. If too much power is applied, the front wheels lose grip and the car understeers sharply.

RWD

Conversely, with rear-wheel drive and front-wheel steering, turning is sharper, but somewhat less stable. Apply too much throttle in this case and the car will tend towards oversteering in corners.

Click here for a diagram which compares Symmetrical AWD vs. FWD and RWD

Balance

Subaru's symmetrical full-time All-Wheel Drive system has been tested, refined and proven in the toughest rallies on earth and has helped the Subaru World Rally Team become one of the most dominant forces in rallying. We utilize the same core technology in both our FIA World Rally Championship rally cars and our production road cars. We hope this site has helped you see how our innovative technologies make driving a Subaru different than driving any other car. Understanding how these technologies work and the fact we continuously improve them can only add to your driving enjoyment. At Subaru, we are proud to build true drivers' cars that offer a world-class combination of agility, stability and traction for superb handling, performance and safety.