Why Torque Is An Important Spec For Vehicles?

Torque and Horsepower are the most important specifications in a car. Most people are familiar with power as it is a frequently used term, but understanding Torque can be a bit tricky if you did not like Physics in your high school.

So, today we will clear the high school doubts first with examples, and automatically this question will be answered (while keeping the Physics terminology to a minimum­čśü).

What is Torque ?

Torque is also known as Rotational Force, Moment, Moment of Force, or Turning Effect based upon the field of study. In Physics/ Mechanics, Torque is the rotational equivalent of linear force.

Here, Rotational Equivalent means the force that is applied to an object, and instead of moving linearly (i.e. up and down), the object rotates/ twists around a fixed axis.

Engine Interiors
Interior Of An Image

The second definition of Torque according to Wikipedia is the product of the magnitude of the force and the perpendicular distance of the line of action of a force from the axis of rotation.

How To Measure Torque?

SI Unit of Torque is Nm (newton meter). 1 Nm can be defined as the Torque which is generated when a force of 1 newton is applied perpendicularly to a lever arm that is 1 meter long.

In western countries, Torque is also measured in lb-ft (pounds-feet). 1 lb-ft is precisely equal to 1.3558179483314 Nm. For conversions between Nm and lb-ft, you can visit this website: Nm to lb-ft convertor.

How To Calculate Torque?

The formula for calculating torque is
Simply,
T = r * F
where,
T is the torque
r is the distance between the fixed axis and the point where we apply the Force F),
F is the applied force

Factors on which the Torque depends

1. Force: Since Force and Torque are directly proportional to each other, the greater the force, the greater the torque becomes.

2. Lever Arm Length: This refers to the distance between the point around which we measure torque and the point where we apply the force.

3. Angle between Force and Lever Arm Vectors: In simple terms, this means the angle at which the force is applied.

Real Life Examples of Torque

1. Whenever we open a water bottle, we apply some rotational force on the cap. This rotational force is nothing but torque.

2. Opening a door is still the most classical example of Torque.

3. Using a wrench to tighten a bolt.

4. The hands in a clock/ watch.

5. Pedaling a bicycle.

6. Pistons in an engine (discussed in detail in the following section).

Torque in an Engine

In a vehicle, the torque describes its ability to turn the crankshaft. The pistons push on a lever called Journal, which causes the crankshaft to rotate, the crankshaft rotates the transmission, the transmission rotates the driver axles, the driver axles rotates the tires, and hence your car moves.

So, the higher the torque, the higher the force on tires, and the higher the pickup.

Engine Torque Animation
Crankshaft (red), Pistons (gray) in their cylinders (Blue), and Flywheel (black)

Importance of Torque in Vehicles

Torque helps in accelerating a vehicle. Therefore, 0-60 mph time of cars is also dependent upon the torque along with the horsepower. If a car provides a good amount of torque, then the car will accelerate faster and a greater force will be exerted on its tires. Higher torque means faster 0-60mph time.

The torque in pickup-type vehicles is always large. For example, GMC Hummer Pickup provides a far greater torque than a Volkswagen Tiguan. The reason for this is also the same. When a truck or a bus is fully loaded, the pistons must provide enough force to rotate the crankshaft.

The torque in diesel engines is always greater than the petrol engines. The petrol engine in Toyota Fortuner has a capacity of 3956cc which produces 376Nm of torque. Whereas, the diesel variant of the same car has 1251cc lesser capacity and still it manages to provide a maximum torque of 420 Nm.

The reason behind it is that diesel engines provide longer strokes. In simple terms, the longer the pistons travel in the air, the more air it compresses in the cylinder and the greater the potential energy becomes, and hence the greater the torque becomes.

Torque Vs. Horsepower

Torque and Horsepower are so related to each other and still so different from one another. I think they are complementary to each other.

Torque is the engine’s rotational force. It means the amount of work an engine can do. on the other hand, horsepower means how quickly that work can be done.

In layman’s terms, horsepower means how hard can you hit a wall with your car, and torque means how far can you go after hitting that wall. A professional biker and an engine geek once shared this beautiful example. A more perfect example does not exist.

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