AWD Systems
Volvo's electronic all-wheel-drive system now comes with Instant Traction. This new technology (which Volvo is the first automaker in the world to introduce) improves start-up traction and enhances traction on slippery surfaces. Developed by the Swedish company Haldex, a nonreturn valve is connected to software that controls the base torque programmed into the AWD system. What this means is when starting off from a standstill, torque (about 60 pound-feet worth) is precharged in the system, because the nonreturn valve prevents the unit from becoming totally drained of hydraulic fluid. This reduces the amount of wheelspin needed to transfer power to the rear wheels.
In addition, an electronically controlled clutch helps improve traction. The front and rear wheels are automatically synchronized by the AWD system, allowing the multiplate clutch to create and distribute near-instantaneous traction where it's needed. When a front wheel slips just a fraction of a revolution, power is transferred to the rear wheels. This helps braking, throttle release, or when the Dynamic Stability and Traction Control anti-spin system is activated. This computer program compares the ideal behavior of the vehicle with the real-time situation by evaluating steering angle, lateral acceleration, wheel speed, and yaw speed to detect deviations and help to correct them immediately. If your vehicle under-steers when cornering, the system reduces engine power and provides braking, using the inner wheels to get you back on the desired track. Similarly, oversteering the outer front wheels triggers the brakes to help prevent the rear from sliding sideways. The AWD is programmed to continuously communicate to the transmission and stability system to keep things straight and predictable.