Subaru’s Symmetrical All-Wheel Drive: Engineering for Performance
Subaru has long been known for its commitment to all-wheel drive (AWD) technology, and its Symmetrical All-Wheel Drive system is a cornerstone of the brand’s identity. But what exactly makes this system so special, and how does it enhance driving performance?
Understanding Symmetrical AWD
Unlike many AWD systems that are adapted from front-wheel-drive or rear-wheel-drive platforms, Subaru’s Symmetrical AWD was engineered from the ground up with balance and stability as top priorities. In fact, the first Subaru with all-wheel-drive was the Leone Station Wagon, introduced in 1972. The system’s name derives from its unique layout, where the engine, transmission, and driveshaft are aligned longitudinally down the centerline of the vehicle, creating a mirrored design. This symmetrical design, combined with Subaru’s signature horizontally-opposed Boxer engine (found in most Subaru vehicles), results in a low center of gravity and even weight distribution, which are crucial for optimal handling.
Subaru designs its vehicles with AWD in mind from the start, unlike competitors who often add AWD as an afterthought to existing platforms. This integrated approach allows for a more harmonious and efficient AWD system. When driving a Subaru with Symmetrical AWD, the system automatically reduces torque to a slipping wheel, ensuring that power is redirected to the wheels with the most grip. This constant and seamless adjustment helps maintain control and stability, especially in challenging conditions.
Benefits of Symmetrical AWD
Subaru’s Symmetrical AWD offers several key benefits that enhance driving performance:
- Enhanced Traction: By continuously sending power to all four wheels, the system maximizes traction, especially in challenging conditions like rain, snow, or ice. This proactive approach minimizes the likelihood of losing traction in the first place, providing a safer and more confident driving experience.
- Improved Stability and Control: The balanced design of Symmetrical AWD contributes to greater stability and control by minimizing body roll and pitch, particularly during cornering and braking. This translates to more predictable and responsive handling, allowing the driver to maintain better control of the vehicle.
- Increased Efficiency and Durability: The Symmetrical AWD system uses fewer components than many other AWD systems, resulting in reduced energy loss from friction. This design not only improves fuel efficiency but also contributes to a longer lifespan for the vehicle.
- Maximized Power Delivery: Symmetrical AWD maximizes power delivery to each of the four wheels, ensuring that engine power is effectively transferred to the road for optimal acceleration. This is particularly beneficial when taking off from a stop or accelerating out of a corner.
- Increased Ground Clearance: The combination of the Boxer engine’s flat design and the Symmetrical AWD system allows Subaru to provide a generous ground clearance while maintaining a low center of gravity. This provides a practical advantage for drivers, especially in snowy or off-road conditions.
- Improved Acceleration: With power being sent to all four wheels simultaneously, Symmetrical AWD enhances acceleration by maximizing the utilization of available traction.
- Reduced Maintenance Costs: The simplicity of the Symmetrical AWD system, with its fewer components compared to other AWD systems, translates to lower maintenance costs over the vehicle’s lifespan.
Components and Technology
Subaru’s Symmetrical AWD system comprises several key components:
- Horizontally-Opposed Boxer Engine: This engine design features cylinders that lie flat and oppose each other, contributing to a lower center of gravity and smoother operation. The Boxer engine’s longitudinal placement, in line with the drivetrain, allows for a more direct transfer of power to all four wheels.
- Symmetrical Drivetrain: The drivetrain components, including the transmission, which is centrally located, and the equal-length driveshafts, are aligned symmetrically along the centerline of the vehicle, ensuring balanced power distribution.
- Viscous Coupling Limited-Slip Differential (VCD): This system, used in manual transmission models, splits torque 50/50 between the front and rear wheels and utilizes a viscous coupling to transfer power to the wheels with the most traction when slippage occurs.
- Active Torque Split AWD: This system, used in CVT models, typically maintains a 60/40 front/rear torque split and uses sensors to adjust the split dynamically based on driving conditions.
- Variable Torque Distribution AWD: This system, found in WRX models, offers a sportier driving experience with a 45/55 front/rear torque split that helps reduce understeer and improve cornering.
It’s important to note that Subaru offers different variations of its Symmetrical AWD system to cater to different driving needs and vehicle types. This allows Subaru to fine-tune the system’s performance characteristics for specific models and applications. For a more detailed comparison of these variations, refer to the table below:
| Viscous Center Differential AWD | Active Torque Split AWD | Variable Torque Distribution AWD | Driver Control Center Differential AWD |
|---|---|---|---|
| Torque Split (F/R) | 50/50 | 60/40 | 45/55 |
| Models Equipped | Manual Subarus | CVT-equipped Subarus (except WRX) | WRX (with CVT) |
| Differential Type | Open | Open | Open |
Performance in Different Conditions
Subaru’s Symmetrical AWD system excels in various driving conditions:
- Snow and Ice: The system’s ability to continuously distribute power to all four wheels provides exceptional traction on snow and ice-covered roads, enhancing safety and control. When combined with Subaru’s X-Mode, which adjusts engine throttle, transmission shift points, and AWD coupling force, the system’s performance in snowy conditions is further enhanced. X-Mode also activates Hill Descent Control at low speeds, aiding in safer maneuvering on slippery slopes.
- Rain: Symmetrical AWD improves stability and provides a quicker response to wet roads, helping drivers maintain control in rainy conditions. The system’s balanced design and continuous power distribution ensure that traction is maintained even on slippery surfaces, reducing the risk of hydroplaning and enhancing overall safety.
- Off-Road: The system’s balanced design and constant power distribution make Subaru vehicles adept at handling rough terrains, providing the necessary traction and stability for off-road adventures. The symmetrical power distribution optimizes grip and traction by ensuring that each wheel receives the appropriate amount of power, allowing the vehicle to navigate challenging off-road obstacles with confidence.
Comparison with Other AWD Systems
While many automakers offer AWD systems, Subaru’s Symmetrical AWD stands out due to its unique design and focus on balance. Unlike some systems that primarily function as front-wheel drive or rear-wheel drive and only engage AWD when slippage is detected, Subaru’s system is always active, ensuring consistent traction and stability. This proactive approach, combined with the symmetrical layout and low center of gravity, gives Subaru vehicles a distinct advantage in terms of handling and performance.
For example, Audi’s Quattro AWD system is also highly regarded for its performance. However, Subaru’s Symmetrical AWD system offers a compelling combination of capability, price, and fuel economy that is hard to beat. This makes it an attractive option for drivers seeking a balance of performance, practicality, and value.
Conclusion
Subaru’s Symmetrical All-Wheel Drive system is a testament to the brand’s commitment to engineering vehicles that deliver exceptional performance and safety in all conditions. By combining a symmetrical drivetrain layout with a horizontally-opposed engine, Subaru has created an AWD system that provides enhanced traction, improved stability, and increased efficiency. The system’s various components, including the viscous coupling limited-slip differential, active torque split, and variable torque distribution, work together to optimize performance for different driving scenarios and vehicle types.
The impact of Symmetrical AWD extends beyond just technical specifications. It has become a defining characteristic of the Subaru brand, contributing to its reputation for reliability, capability, and all-weather performance. This resonates with driving enthusiasts who value a vehicle that can confidently handle a variety of conditions, from snowy roads to off-road trails. By consistently delivering on its promise of enhanced driving performance, Subaru’s Symmetrical AWD has solidified its place as a leader in AWD technology.