The letters VDC are cryptic, but in the context of a car, they stand for something potentially life-saving — Vehicle Dynamic Control or Vehicle Dynamics Control.
This technology attempts to combat the loss of steering control that can occur in slippery conditions. Essentially, what VDC means in a car is the same thing as electronic stability control (ESC), which has been mandatory on vehicles sold in the United States since 2012. Automakers that refer to ESC as VDC include Infiniti, Nissan, and Subaru.
Electronic stability control systems use computerized technology to detect wheel slippage before it is evident to the driver. Then, to ward off more significant traction loss, they apply countermeasures that the driver cannot.
For instance, the VDC system might apply the brakes to individual wheels to counteract slipping. If a vehicle begins to understeer — in other words, if it is not responding to steering wheel input to turn and instead pushes forward in a straight line — VDC will apply the brakes on the outer front wheel forcing the car to turn. VDC does not steer the vehicle. Instead, it provides inputs that enable the driver to continue to steer the car in the direction they want it to go.
During normal driving, a VDC system continuously monitors steering and vehicle direction. It compares the driver's intended direction as determined by the steering wheel angle to the vehicle's actual direction of travel. Typically, the intended path and actual travel path are the same, but if there are wheel slippage and a loss of traction, they can differ. The system determines the difference between intended and actual direction and electronically issues orders to the car's systems to mitigate the problem.
Subaru VDC (Vehicle Dynamics Control) is a form of electronic stability control. It uses a network of sensors installed on the vehicle to monitor wheel speed, steering-wheel position, yaw rate, and lateral acceleration. Should the information provided by the sensors suggest to the computer control unit that the vehicle is not moving in the direction intended by its driver, the system will take steps to try to correct the situation.
Most Subaru models have standard all-wheel-drive, so the Subaru VDC system uses AWD to maximize traction and restore vehicle stability. Often this occurs before the driver even realizes there is an issue. If this fails to restore the proper traction and stability, VDC will take further corrective action by adjusting torque applied to the front and rear wheels and applying the brakes to individual wheels.
Subaru says that with AWD, the braking wheel will regain traction more quickly than on a two-wheel-drive vehicle, coaxing the car back onto its intended path sooner. Beyond that, the system might also alter engine timing and reduce fuel flow to the engine to limit torque, further enhancing stability.
Both Nissan and Infiniti vehicles have a Vehicle Dynamic Control (VDC) system, and it functions in the same manner as most electronic stability control systems. It uses various sensors to monitor driver inputs and vehicle motion, gently aiding the vehicle's ability to stay on the driver's intended path.
Nissan and Infiniti's VDC helps control and limit both understeer and oversteer. As mentioned earlier, a car that is understeering is not responding as rapidly as desired to an input to turn right or left. Instead, it pushes forward.
By contrast, a car that is oversteering is turning more rapidly than desired, giving the driver the impression that the car's rear end is coming around. If oversteer goes uncorrected, the vehicle will spin.
To counteract these unwanted actions, the Nissan/Infiniti VDC system controls brake pressure to individual wheels and regulates engine output to help the driver maintain control of the vehicle in both understeer and oversteer situations. To help maintain overall stability as you drive, it uses brake pressure to reduce wheel slip on a drive wheel that is losing traction by transferring power to a non-slipping drive wheel on the same axle.
The Vehicle Dynamic Control feature helps your car maintain proper traction when driving in adverse conditions. But when the vehicle is stuck in snow or mud, the VDC reduces engine output, and you may need to turn it off to get your vehicle out. In most Infiniti and Nissan vehicles, there is a VDC Off switch.
A VDC system is a great tool to help a driver to maintain control of a vehicle, but it cannot prevent loss of vehicle control in all driving situations. The driver is always responsible for the vehicle's safe operation, so be sure to adjust your speed and driving inputs for the road and weather conditions you encounter.
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