# Torque vectoring:why does the inside front wheel also have same torque

• marellasunny
In summary, an open differential provides a 50-50 torque split between front and rear wheels, while a limited-slip differential allows for more torque to be sent to the wheel with less traction. This is done to reduce understeer.
marellasunny
My question relates to torque vectoring during a turn(high speed). Wikipedia says torque vectoring is mainly done on the rear wheels during a turn. The front wheels receive the same amount of torque though. Why do the front wheels receive the same amount of torque during a turn?

Say my engine produces 500Nm torque. My centre differential distributes it 60% to the rear(=300Nm) and 40% to the front(=200Nm). Say also,my front and rear axle differentials multiply the torque by 3 times.

So,if I am turning left,my rear right wheel gets a torque of 900Nm after torque vectoring(the rear left wheel is at 0Nm). But,according to the videos and wikipedia,the front wheels are each at 300Nm. Why? [I think this promotes understeer].

Please have a look at this diagram from Nissan Juke taking a left turn,the front wheels are each at 25%:http://www.nissan.co.za/en/web/models/JUKE/Performance/images/1365681727649049510.jpg

In the absence of any special techniques or fancy differentials (and most AWD cars do not have a limited slip diff on the front wheels), an open differential will always provide a 50-50 torque split. As for why this is done? Because it is simple, and in most cases, a fancy front diff on an all wheel drive car provides little benefit. On a front-wheel drive car, the answer is quite different - many high performance FWD cars do have specialized differentials that carefully control the torque going to each wheel in a turn.

One other point is that having unequal torque on the front wheels is unpleasant to drive because it causes torque steer.

Here is my understanding.

There are only 2 types of differential: open or limited-slip. Both divide power to each wheel.

The open diff transfer the power from one wheel to another by varying the wheel rpm (increasing one, reducing the other). So, as said previously, the torque output is always 50/50, even if the power isn't the same.

This is the best setup for typical driving, as wheel rpm is different from left to right when taking a turn. Not adjusting the rpm would mean losses as some dragging would be involved while taking a turn. As an added bonus, the open diff is the most economical one to build.

But when you have different traction characteristics from left to right, the one having the lowest coefficient of friction may start to slip and hence waste power (to the point of losing it all, if the other wheel has stopped rotating).

The only way to solve that problem is to lock the right and left axles together. The best way is to do it by some friction mechanism, thus the limited-slip diff. The friction may comes from clutches, cones, worm gears (Torsen) or even the brake system and it may be preset or computer controlled; still it has the same effect in the end and that friction power represents a loss.

In the extreme case of having a completely locked diff, one can see that both wheels have the same rpm, so the only option for transferring power from one wheel to another is to transfer torque. If one wheel is not touching the ground, then it is easy to understand that the full power goes to the wheel that touches the ground even if both wheel are rotating. This is obviously the best setup for a limited traction situation, preferably in a straight path.

Now to address the present problem. AWD like the ones the OP talks about are usually designed to be mostly FWD, sending power to the rear wheels only when traction is weak. First of all, we can note that having a torque difference on front-wheel-steered FWD vehicles may induce torque-steer.

So, the front diff should be an open diff (50/50) since it is mostly used for everyday, no-traction-problem, situations. When you loose traction, then you switch to AWD. And because you know your in a low traction situation, making the rear diff a limited-slip one makes sense, since it is always used in low-traction situations.

As for the understeer problem stated in the OP, sending the power to the rear wheels in a low traction situation is done exactly for that: reducing understeer.

http://www.autos.ca/auto-tech/auto-tech-limited-slip-vs-torque-vectoring/
http://www.popularmechanics.com/cars/news/4225886
http://torque-vectoring.belisso.com/

## 1. Why is torque vectoring necessary in vehicles?

Torque vectoring is necessary in vehicles because it allows for better handling and control, especially in challenging driving conditions. By controlling the amount of torque delivered to each wheel, torque vectoring can improve traction and stability, resulting in a smoother and safer driving experience.

## 2. How does torque vectoring work?

Torque vectoring works by using sensors and electronic controls to monitor the speed and traction of each wheel. Based on this information, the system can adjust the amount of torque delivered to each wheel, either by increasing or decreasing it, to improve handling and stability.

## 3. Why does the inside front wheel also have the same torque in torque vectoring?

The inside front wheel also has the same torque in torque vectoring because it is responsible for transferring the weight and power of the vehicle during turns. By delivering the same torque to both front wheels, torque vectoring helps to maintain balance and prevent understeering.

## 4. Can torque vectoring be turned off?

Yes, torque vectoring can be turned off in some vehicles. However, it is not recommended as it may affect the vehicle's handling and stability, especially in challenging driving conditions. It is best to consult the vehicle's manual or a professional mechanic before turning off torque vectoring.

## 5. Are there any drawbacks to torque vectoring?

One potential drawback of torque vectoring is that it can increase the wear and tear on the vehicle's drivetrain components, such as the differential and axles. Additionally, it may also add weight and complexity to the vehicle, which can impact fuel efficiency and cost. However, the benefits of improved handling and safety generally outweigh these drawbacks.

Replies
7
Views
2K
Replies
6
Views
1K
Replies
8
Views
2K
Replies
9
Views
7K
Replies
2
Views
2K
Replies
7
Views
2K
Replies
6
Views
7K
Replies
2
Views
2K
Replies
20
Views
15K
Replies
8
Views
11K