When you’re in the middle of doing vehicle research for your vocational fleet, there’s no doubt you’ve come across the term “torque” a vast majority of the time. Have you developed a deep understanding of its meaning? This guide in Work Truck’s Fleet 101 series will have you speaking about the concept like a pro in no time.
What is Torque?
First off, we need to set the record straight: although related to one another, horsepower and torque are two different things. While both are an indicator of power, torque will likely be of more interest to those in the world of vocational fleet. Simply put, torque is an indicator of towing power, while horsepower is the maximum power available to a vehicle and has more to do with speed and the rate at which an engine accomplishes work.
For a basic comparison, you’ll likely see many sportscars with higher levels of horsepower than a truck meant for heavy lifting and vice versa.
How is it Measured?
You’ve likely gotten lb.-ft. and ft.-lb. mixed up and weren’t even aware there was a difference!
According to Engine Labs, a lb.-ft. (also referred to as a newton-meter in the metric system) is a unit of torque and a vector measurement created by one pound of force acting on a one-foot lever. On the other hand, a ft.-lb. is a measurement of work. Work is the measurement of force over a given distance. It measures the energy required to move a one-pound object one foot of linear distance.
In simpler terms, lb.-ft. is the official measurement of torque, the force that helps the truck start moving from a stop and pulls it up steep hills.
BMW states that the formula for torque is as follows:
Torque = force (N) x lever arm (m)
Newton (or pound) stands for the acting force, while meters (or feet) stand for the length of the lever arm being used to enact the twisting force.
Where Does it Come From?
Essentially, torque is the rotational force of an engine that measures how much of that force is available when an engine exerts itself, according to Toyota. As the pistons in an engine move up and down on an engine’s crankshaft, torque is the force that keeps it constantly rotating at a certain speed. From there, torque is shifted to the vehicle’s wheels through the transmission and drivetrain.
For an even simpler visual, think about twisting a jar open with your hand, turning a wrench to tighten a bolt, or even opening a door by rotating a doorknob.
In a piece for Work Truck sister publication Heavy Duty Trucking, writer Rolf Lockwood stated, “In an engine, torque is generated by the pressure load of the expanding gases on the top of the piston times the stroke, meaning how far the piston moves. Two basic principles apply: torque is stronger at the lower end of an engine’s operating range, while horsepower is higher at the upper end; and a bigger displacement engine will produce more power than a smaller one, simply because there’s more area for combustion to force down those pistons.”
What Causes Differences in Torque?
All trucks are not created equal when in comes to torque, and that’s because the level of torque produced is impacted by the amount of air flowing through the engine. Larger engines produce more torque because they pump more air.
Piston length will also cause differences in torque. Diesel engines, for example, will create greater torque because the piston moves relatively farther, resulting in longer strokes.
Why Does it Matter?
With all the technical information out of the way, now it’s time to discuss the benefits of torque for vocational fleet drivers. The low-end revolutions per minute (rpm) generated by higher levels of torque is what allows the engine of a truck to easily carry heavy loads and move quickly after coming to a stop. For example, trucks will move slowly when moving up a hill with a trailer or heavy load. Therefore, the engine rpm will be low, enabling the vehicle to operate smoothly for the task at hand.
“In simple terms, torque is the twisting power of the engine to get and keep your vehicle moving. A fleet customer might benefit from a truck with more torque if they have heavy payload or towing needs, as higher torque combined with low engine rpms often leads to better performance when starting from a stop. Diesel engines naturally have high torque at low rpms, which is one reason they are often preferred for heavy-duty applications. Selecting the right powertrain will vary across fleet customers based on need, which is why GM offers a range of engines, both gas and diesel, across our line-up,” said Dan Tigges, commercial product and sales support manager for GM.
Dave Sowers, head of Ram Commercial Marketing, said, “Businesses expect their vehicles to do it all, so power and torque are important. Delivery services require ample power and torque, whether they are an expediter or a final-mile service, to cover miles of interstate, city streets, and all the rolling topography in between. Whether it’s a landscaping company towing a trailer, a plumber hauling heavy pipes, or a contractor carrying marble countertops, power and torque are necessary to get in and out of the job site. There isn’t a ‘one-size-fits-all’ solution, but Ram offers light- and heavy-duty trucks and vans for all, no matter their line of work.”
Something important to note is torque isn’t the only factor that affects a vehicle’s towing capacity. Components such as wheels, tires, suspension, and transmission also play a part in the overall equation.