In the simplest terms, torque refers to the twisting force that is exerted by an engine’s crankshaft. This torque is fed into the drivetrain to eventually drive the wheels, which gets the car in motion.
How is torque created?
In an internal combustion engine (ICE), torque is generated by the downward forces on the crankshaft, exerted by the rods which connect the pistons to the crankshaft (also known as connecting rods). This principle applies to all combustion engines, regardless of fuel source, and stems from the crankshaft’s ability to convert linear force (from the piston itself) to a rotational force.
Electric motors also generate torque, but instead of converting linear force into rotation, they convert electro-magnetic forces inside the motor (supplied by the battery pack) into rotation. Simply imagine the electric motor’s windings and magnets as performing the same job as pistons do in an ICE to understand the same basic principle.
Related: For a more-detailed explanation of electric motors and their torque output, take a look at this article on CarThrottle.com.
Units of measurement
Torque is measured in Newton-meters (N.m), according to international (SI) standards, from where it’s also used to calculate power outputs. It basically indicates the ability of the engine to perform work, and is independent of rotational speed. Don’t confuse this with the power output, which is an indication of the amount of work the engine performs.
In certain countries, the metric measurement system has not been fully adopted, with the antiquated imperial system still serving as reference point. In these countries, the measurement unit for torque is in lb. ft (Foot-Pound), essentially an imperial measure that equals the SI measure multiplied by a constant correction factor.
1 Foot-Pound equals 1.356 Newton-meter (N.m), so converting from lb. ft to N.m entails multiplying the imperial value by 1.356. Conversely, going from N.m to lb. ft thus means dividing the imperial value by 1.356.
Related: For a visual explanation of the difference between power and torque (and a host of other cool technical content), watch this excellent video on the Driving 4 Answers YouTube channel.
Why is torque important?
The more torque an engine has, the better it is for hard work, such as towing a trailer or climbing a steep hill. Many engines are optimised to produce as much torque as possible, over as wide a rev range as possible, to give a broad power band. Put another way, they try to make the area under the torque curve as large as possible, because that indicates the amount of work the engine can do.
