Whether you are an off-road enthusiast or someone who uses cars just to get from one place to another, you must have heard of a 4×4 or an all-wheel-drive car. The term, All-wheel-drive, is pretty self-explanatory. The power or torque is supplied to all the wheels of the car. But in order to understand why a 4×4 system is needed and how it actually works, we must first understand the functioning of a differential. Let us make you learn about this technology through this easy to understand article!
Also read: What is Downsizing and Turbocharging?
What is a Differential?
The differential is a completely mechanical component in a vehicle. It is truly an engineering marvel. A differential is found at the centre of both the axles of your car. It can also be located at the centre of the shaft connecting both the differentials. The simple purpose of a differential is to distribute power/torque coming from the engine to the wheels. This lets the wheels of a car rotate at different speeds. Let us understand with an example, why it is necessary for wheels to rotate at different speeds.
When a car goes around a corner, the distance covered by the outside wheels is larger than the inside wheels. To maintain the stability of the car, wheels need to move at different speeds. A differential allows this and ensures a smooth operation of the vehicle. This is further illustrated in this video.
AWD or 4×4 System
Generally, for a normal car, this differential is open. This means that the torque is divide equally between both wheels. But for an off-roading vehicle, normally the feature of the rear-locking differential is available. What this does is essentially connect the two wheels together and make them rotate with each other. This helps when one of the tyre does not have enough traction. There is no point in supplying this tyre with power because it is not in contact with the ground. So instead of this, all the power can be sent to only one wheel, which can put into the ground and make the vehicle move.
Similarly, when there are three differentials in the car, one at the rear, one at the front and one in the centre, it offers a huge degree of flexibility of how to out down maximum torque on the ground. However, it is an extremely complex procedure when three differentials are involved. This system is capable of recognizing the traction that each wheel has and supply the torque accordingly. As you would imagine, such systems are found in hardcore top-end off-roaders because of extremely high costs.
Therefore, to keep the costs in check as well as provide effective off-roading capabilities, one or two of the three differentials can be kept open. The open differential will not provide variable torque to each wheel but will simply split the torque equally. This ensures that the system doesn’t get too expensive and also the purpose of a 4 Wheel system is also served effectively.
Although, 4 Wheel Drive and All-wheel drive might seem similar to someone and they largely are, still there is a subtle difference between the two. In All-wheel drive systems, all the wheels receive torque as and when the situation demands because of a centre differential. The entire system is very flexible. However, in the 4×4 system, there is a transfer case at the centre connected to the engine/transmission. This can be shut down entirely and the vehicle can become completely rear-wheel or front-wheel drive.
The functioning of 4×4 system and AWD system can be further understood with the help of this video.
To summarize, both AWD and 4WD systems are the most important parts of any off-roading vehicle. When going off the tarmac, the dirt roads can throw any challenge at you. It will have large potholes, uneven surfaces and many undulations. You can almost be sure that at no time will all your car’s wheels stay in contact with the ground. That is why it is of prime relevance, to allow power/torque delivery to that particular wheel, which is still on the ground and can carry the vehicle out of the difficult situation.
We hope that this post has made it better for you to understand the working of the AWD or 4WD systems.