Torque is a measurement of the force that causes an object to rotate around an axis. It’s often described as a twisting force, like when you tighten a bolt using a wrench. Along with horsepower, torque is most frequently talked about in relation to engines. Automakers usually display torque numbers along with horsepower to show the power output of a vehicle.
What Is Torque in Cars?
Torque is the rotational force created by an engine. It’s created when the combustion in a cylinder applies a downward force on an engine’s crankshaft. As the engine produces torque, it spins the crankshaft that’s connected to the transmission. The gears on the transmission convert the torque and allow the vehicle to move forward.
Torque is what determines how much work an engine can do or haul. A heavier vehicle will need more torque to move the wheels than a lighter one. The amount of torque is related to the amount of air flowing through an engine. Since larger engines pump more air, they produce more torque. This is also why both turbochargers and superchargers can boost torque as well as horsepower.
Diesel Engines & Torque
Diesel engines usually have more torque than gasoline-powered engines for several reasons. They have higher compression ratios, faster combustion, and a longer stroke length. All modern diesel engines in America have turbochargers, which forces more air and oxygen into the engine.
Turbochargers give diesel engines more power and make them more efficient. Although some older diesel engines are naturally aspirated, they produce significantly less torque. The high torque ratings of diesel engines is the main reason the Cummins, Powerstroke, and Duramax engines have grown in popularity over the years.
Why Is Torque Important?
Horsepower may get all the credit, but torque is important too. Without torque, your engine wouldn’t be able to rotate, and you wouldn’t get any power. More horsepower might lead to faster speeds, but torque also affects your vehicle’s performance.
Torque is what gives trucks their immense hauling power. The more torque a vehicle has, the more it will be able to tow. Lower gears have higher torque and are better for towing.
Automatic transmissions can usually tow heavier loads since they have a torque converter. Manual transmissions are usually better for hauling off-road or on unlevel terrain since you have more control.
Lower gears may be better for hauling, but they’re also better for accelerating. Higher torque means more low-end power, which allows a vehicle to accelerate at low RPM levels. If you’ve ever been in top gear and had trouble passing a car on the highway, it’s because torque levels are lower in higher gears. Therefore, you won’t be able to accelerate as quickly at high speeds as you could at lower ones.
At peak torque, you can feel the engine’s power the most. Torque is that feeling that pushes you back in your seat when you hit the accelerator pedal.
Because more torque equals better low-end power, it also comes in handy when off-roading. You’ll be able to accelerate better at lower speeds. This helps you crawl over rocks and through the mud at a slow and steady pace without having to constantly press the gas pedal. Not only is this better for the engine, but it gives you more control. Of course, the gearing and crawl ratios factor in as well.
How to Calculate & Measure Torque
Since torque is force multiplied by distance, you can calculate torque by multiplying the force by the distance from the center. This is why the units of torque are pound-feet.
For example, if you’re tightening bolts with a one-foot long wrench and you exert 150 pounds of force, you’re producing 150 pound-feet of torque. Calculating the torque generated when tightening a wrench may seem easy, but it’s much more complex when it comes to engines.
Engine torque is best calculated using a dynamometer, also known as a dyno. Dynos measure an engine’s torque and RPM levels, then use those numbers to calculate the horsepower. Those figures are then recorded on a dyno graph. Torque can be measured at the wheels or at the engine, depending on the type of dyno used.
If you know the horsepower and engine speed, you can also manually calculate torque using this equation:
Torque = (Horsepower x 5,252)/RPM
You’ll have to multiply the horsepower by 5,252 as horsepower and torque are always equal at 5,252 RPM. Then, you divide that number by the RPM, or engine speed, to get the torque. But using a dyno is a much more efficient and accurate way to calculate torque.
The Future of Torque
As electric vehicles take over the automobile industry, torque as we know it is changing. Unlike gasoline and diesel-fueled vehicles, electric cars have a motor instead of an engine. Electric vehicles have instant torque, meaning they reach peak torque at zero RPM. All the electricity created by the motor from the time the electric power is applied becomes instant torque.
As more manufacturers add to their electric vehicle lineup, it will be interesting to see how torque factors into the future of automobiles. Torque isn’t going anywhere, but the way you experience it might change.
Sources: Khan Academy, Car and Driver, Auto Blog, Motor Authority, Forbes, How Stuff Works, EPA, US News, Jalopnik, Engineering Explained