Torque vectoring is a phrase you may have heard while researching your next car, but what is it?
Put simply, it’s a computer-controlled system to distribute an engine’s power across the left and right sides of a car. By controlling the power across the axle more effectively, the car is able to corner with more grip and turn into a bend quicker.
Cars have to be able to go around corners for obvious reasons, but doing so isn’t as simple as you might think. Think of a car’s wheels as you go round a bend – the outside wheels have to travel further than the inside wheels in the same amount of time. To do this while also powering them requires a device called a differential (shown in the image below).
Torque vectoring using a differential
A differential, or diff, takes torque from the engine then distributes it between the powered wheels. Most conventional cars have an ‘open’ diff, meaning up to 100 per cent of the engine’s power can go to either wheel, following the path of least resistance. This means, when one wheel of an open diff car is stuck off-road, it will usually spin the opposite uselessly.
If there was a way to stop all the torque reaching just one wheel then both wheels could be used together more effectively. Shuffling torque from one side to the other is known as vectoring. Unsurprisingly, torque vectoring, like many modern drivetrain technologies, was developed through motorsport. In rallying, Mitsubishi did much early work with this technology, giving their Evo race cars a major advantage.
Don’t you mean a limited-slip differential?
Well… yes and no. A limited-slip differential does limit the capacity for one wheel to spin while the other has grip, but it’s a mechanical connection with no computer intervention. The computer controlled nature of a torque vectoring system not only limits the spin of one wheel but can actively redistribute the engines power to the wheel with the most grip.
A differential with torque vectoring will typically have electronically-controlled clutches that vary the amount of slip allowed by the differential according to the grip available to the wheels and what the driver’s asking of them.
Torque vectoring through braking
For smaller front-wheel-drive hot hatches such as the Volkswagen Polo GTI, having a complex electronic diff under the bonnet along with the gearbox, axle, wheels and engine would be overkill, and it’d make the Polo GTI too expensive for its price point. Modern braking systems, however, can replicate the actions of a limited slip differential.
Known as torque vectoring through braking (known as XDS in Volkswagen Group cars), the system brakes the inside wheel during a turn. As the inside is braked, more power is sent to the outside wheel mimicking the rotational effect a torque vectoring differential applies to a car – known as yaw. Increasing braking force increases the yaw effect, turning the car into the corner.
What diff-erence will it actually make?
Most smaller and slower cars don’t have much torque to vector, so come with cheaper open diffs – this means your wheels will go round a corner at different speeds but can’t be powered individually. More powerful and performance-biased cars are more likely to have torque vectoring as standard or as an option.
On the road, a car equipped with torque vectoring should feel more secure and stable at speed, especially through corners. You should also notice that the front of the car is more willing to pull itself into a corner or ‘turn in’ more effectively before the front wheels begin to understeer (lose grip).
The glaring one is, if you don’t do lots of enthusiastic driving, there’s very little point in having the expense and complexity of a torque vectoring system. Ultimately, it’s another outlay and another sophisticated electronic component that could go wrong down the line.
If you have a torque vectoring through braking-type system then you might notice you get increased brake wear. Because the brakes are partially used, even when accelerating, they do tend to wear-out faster leading to potentially expensive replacements.
And there we have it, torque vectoring and differentials explained. Still don’t understand? Let us know in the comments below and we’ll do our best to answer!
Still don’t know what torque is?
Why not take a look at our handy guides to torque and horsepower to help you understand some of the most commonly used phrases in car reviews. Whilst you’re there why not take a look at our guides to traction and stability control – two other systems that keep us safe on the roads.