Torque Vectoring is a new technology being employed in automobile differentials. A differential is used to transfer engine torque to the wheels. Torque vectoring technology provides the differential with the ability to vary the amount of power sent to each wheel. This method of power transfer has recently become very popular in all-wheel drive vehicles. A basic torque vectoring differential can be found on some newer front-wheel drive vehicles as well.[1] As technology in the automotive industry improves, more and more vehicles are being equipped with torque vectoring differentials.
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Torque vectoring is an idea that builds off of the basic principles of a standard differential. A torque vectoring differential performs basic differential tasks while also allowing torque to be transmitted independently between wheels. This torque transferring ability improves handling and traction in almost any situation. Torque vectoring differentials were originally used for racing applications. Mistubishi rally cars were some of the earliest vehicles employing this technology.[2] 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 very complex. The main goal of torque vectoring is to independently vary the torque being sent to each wheel. Differentials are generally consisting of only mechanical components. A torque vectoring differential needs a specific electronic monitoring system on top of the standard mechanical components. This electronic system is in charge of telling the differential when and how to vary the torque output. Due to the number of wheels receiving power, a front or rear wheel drive differential will be less complex than an all-wheel drive differential.
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 is only in charge of varying the torque between two wheels. This will make the differential mechanically less complex. The electronic monitoring system will only have two wheels to monitor, making it less complex as well. A front-wheel drive differential has several factors to take into account. The rotational speed as well as the steering angle of the wheels needs to be monitored. As these two factors vary during driving, different forces are exerted on the wheels. The differential will monitor these forces and adjust the torque accordingly. Many front-wheel drive differentials have the ability to either increase or decrease the torque being transmitted to a certain wheel.[3] This ability improves a vehicle’s capability to maintain traction in poor weather conditions. When one wheel begins slipping, the differential can reduce the torque being sent to that wheel, effectively braking the wheel. The differential will also increase the torque being sent to the opposite wheel, helping keep the vehicle stable and balance the power output. A rear-wheel drive, torque vectoring differential will work in the same way as a front-wheel drive differential with the exception of monitoring the steering angle.
Most torque vectoring differentials can be found on all-wheel drive vehicles. A basic torque vectoring differential will vary the 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 of the torque. If needed, more torque can be transferred between the front and rear wheels to improve the vehicles performance. An example would be a vehicle where the standard torque distribution is 90% to the front wheels and 10% to the rear wheels. Under harsh conditions, the differential can change the distribution to 50/50. This new distribution spreads out the torque more evenly between all four wheels. Having a more even torque distribution increases the vehicle’s traction.[4]
There are more advanced torque vectoring differentials as well. These differentials build upon the basic torque transfer between the front and rear wheels. They also have the capability of transferring the torque between individual wheels. This provides an even more effective method of increasing a vehicle’s handling characteristics. The differential will monitor each wheel independently and increase or decrease the amount of torque being sent to match the current conditions. Acura’s Super Handling All-Wheel Drive (SH-AWD) is capable of transferring power between the front and rear as well as varying the amount of torque transmitted to each rear wheel. The front wheels, however, cannot receive different amounts of torque.[5] Audi has 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.[6]