Media post: Torque vs. Horsepower: Which One is More Important for Towing?

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Automakers and drivers tend to put a lot of emphasis on torque and horsepower, but these  two terms are not indistinguishable from one another. They represent two very different characteristics of a diesel truck. The former measures the force with which the vehicle moves, while the later measures the speed at which the force is produced. Both can play a role in towing, but one quality tends to be more important than another. If you are looking to do some heavy towing with your truck, learn more about what these qualities actually mean and how they will affect your vehicle’s hauling abilities.

What is Torque?

Torque measures the force at which an object spins around a radial point. In the case of a diesel engine, we are talking about the piston and the crankshaft. When fuel and air burn in the combustion chamber, it forces the piston down, which turns the crankshaft. This is the mechanical force that spins the wheels of the vehicle, thus moving it forward.

Simply put, torque is the force at which the crankshaft is turned. It is measured by the force applied to the crankshaft and how far it turns. It is expressed in terms of pounds-feet—the force applied on a lever times the length of the lever in feet. If the piston applies 100 lbs. of pressure and the crankshaft is 2 feet long, the vehicle is producing 200 pounds-feet of torque (100 x 2 = 200).

What is Horsepower?

Horsepower is the overall power output or the speed at which the work is performed. In this case, it would be how quickly the combustion process forces the piston down, thus turning the crankshaft. The formula for horsepower is torque times the number of rotations per minute (RPM) divided by 5252. Horsepower helps the vehicle build speed at high revolutions. It is directly related to torque, as you need torque to build horsepower. For example, if a vehicle has 200 pounds-feet of torque and is operating at 3,000 RPMs, it has a horsepower of 114hp [(200 x 3,000) / 5,252 = 114).

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How Torque & Horsepower Affect Towing

Both torque and horsepower have an affect on towing, but they serve different functions on the road.

Torque is arguably more important than horsepower when it comes to towing because your vehicle needs to be able to start moving from a still position while carrying a heavy load. The vehicle will need enough torque to move the truck from rest even at low RPMs. If we go back to the equation above, horsepower will be low if the vehicle is starting from rest. That means torque is the main component that will help you haul the load at low speeds.

Most heavy-duty trucks spend the bulk of their time at low speeds except when it comes to the highway. Having a hp rating will help you generate enough power to pass other vehicles on the road, but you probably won’t be going that fast to begin with. The sweet spot when towing tends to be 55-65 MPH.

Torque is essential when it comes to getting moving your vehicle in the first place. A vehicle may have a lot of horsepower at high RPMs but that won’t help you move a heavy load when you first put your foot on the accelerator.

Diesel engines have a longer piston stoke than gas-powered vehicles to build additional torque at low speeds. That’s why most heavy haulers tend to have a diesel engine. You can still tow objects with a gas-powered vehicle but getting started will put additional pressure on the engine because there isn’t enough torque to move the crankshaft.

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Hauling Tips and Considerations

You should never exceed your vehicle’s torque and horsepower limitations, or you risk damaging your engine. The brakes will start to fade, the added weight will sink your tires, and the engine will begin to overheat as the vehicle burns more gas and fuel to put additional pressure on the piston to turn the crankshaft. This can lead to several problems under the hood.

First, it can damage the exhaust gas recirculation (EGR) cooling system, which reduces the temperature of the exhaust before sending it back through the combustion chamber. The added heat can cause the cooling system to break down, which forces you to replace your EGR coolers more often.

Certain makes and models come with known reliability issues, and towing can make the problem worse. The injection control pressure sensor controls the flow of fuel as it moves into the combustion chamber based on how much is needed to power the vehicle. When the weight is increased, so the injection pressure. Check the your ICP sensor on the Powerstroke 7.3 and find a replacement if the injection pressure is off.

Towing forces your vehicle to work harder because it is moving more weight. This creates excess heat and stress.  The pressure can damage individual parts and components, including clamps, gaskets, and seals that prevent leaks in the engine. Find a reliable diesel parts supplier and replace your worn parts to prevent more serious damage.