Torque vectoring is a new technology employed in automobile differentials. A differential transfers engine torque to the wheels. Torque vectoring technology provides the differential with the ability to vary the power to each wheel. This method of power transfer has recently become popular in all-wheel drive vehicles. Some newer front-wheel drive vehicles also have a basic torque vectoring differential. As technology in the automotive industry improves, more vehicles are equipped with torque vectoring differentials.
The torque vectoring idea builds on the basic principles of a standard differential. A torque vectoring differential performs basic differential tasks while also transmitting torque independently between wheels. This torque transferring ability improves handling and traction in almost any situation. Torque vectoring differentials were originally used in racing. Mitsubishi rally cars were some of the earliest used the technology. The technology has slowly developed and is now being implemented in a small variety of production vehicles. The most common use of torque vectoring in automobiles today is in all-wheel drive vehicles.
The idea and implementation of torque vectoring are both complex. The main goal of torque vectoring is to independently vary torque to each wheel. Differentials generally consist of only mechanical components. A torque vectoring differential requires an electronic monitoring system in addition to standard mechanical components. This electronic system tells the differential when and how to vary the torque. Due to the number of wheels that receive power, a front or rear wheel drive differential is less complex than an all-wheel drive differential.
Front/Rear Wheel Drive Vectoring
Torque vectoring differentials on front or rear wheel drive vehicles are less complex, yet share many of the same benefits as all-wheel drive differentials. The differential only varies torque between two wheels. The electronic monitoring system only monitors two wheels, making it less complex. A front-wheel drive differential must take into account several factors. It must monitor rotational and steering angle of the wheels. As these factors vary during driving, different forces are exerted on the wheels. The differential monitor these forces, and adjusts torque accordingly. Many front-wheel drive differentials can increase or decrease torque transmitted to a certain wheel. This ability improves a vehicle’s capability to maintain traction in poor weather conditions. When one wheel begins to slip, the differential can reduce the torque to that wheel, effectively braking the wheel. The differential also increases torque to the opposite wheel, helping balance the power output and keep the vehicle stable. A rear-wheel drive torque vectoring differential works the same way as a front-wheel drive differential, but doesn't monitor the steering angle.
All-Wheel Drive Vectoring
Most torque vectoring differentials are on all-wheel drive vehicles. A basic torque vectoring differential varies torque between the front and rear wheels. This means that under normal driving conditions, the front wheels receive a set percentage of the engine torque, and the rear wheels receive the rest. If needed, the differential can transfer more torque between the front and rear wheels to improve vehicle performance.
For example, a vehicle might have a standard torque distribution of 90% to the front wheels and 10% to the rear. Under harsh conditions, the differential changes the distribution to 50/50. This new distribution spreads the torque more evenly between all four wheels. Having more even torque distribution increases the vehicle’s traction.
There are more advanced torque vectoring differentials as well. These differentials build on basic torque transfer between front and rear wheels. They add the capability to transfer torque between individual wheels. This provides an even more effective method of improving handling characteristics. The differential monitors each wheel independently, and distributes available torque to match current conditions. Acura’s Super Handling All-Wheel Drive (SH-AWD) can transfer power between front and rear and vary the amount of torque transmitted to each rear wheel. The front wheels, however, do not receive different amounts of torque. Audi produced a torque vectoring system capable of varying the torque received by any wheel of the vehicle. This allows each wheel to receive independent torque amounts to increase the overall performance of the vehicle. In 2012, Mercedes introduced the SLS AMG Electric Drive. Mercedes engineers were also able to make all four wheel motors produce negative torque, which twists the inside wheels back, while the outside wheels get full power, as the vehicle goes around a corner. This negative torque slows the inside wheels when cornering to tighten the car's line, and meter out extra torque left-to-right or front-to-rear to improve the car's balance.
List of systems capable of active left-right torque vectoring
- Audi's quattro with Sport Differential
- BMW's xDrive with Dynamic Performance Control
- Honda's SH-AWD
- Kia's Dynamax™ AWD
- Mercedes-Benz's SLS AMG Electric Drive combined with active front-back torque vectoring
- Mitsubishi's Active Yaw Control
- Nissan Juke
- Saab's XWD
- Ford on several models
- Porsche on several models, when torque vectoring added as an option
- Subaru's AWD on 2015 WRX
- Holden Special Vehicles Gen-F GTS
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