Every description of a car, truck, or SUV includes information about engine power, but what is horsepower versus torque? Horsepower and torque do several important things:
- They enable a car to accelerate onto a freeway.
- They help keep up a high rate of speed
- They allow a car to climb a hill without slowing down too much
- For trucks and SUVs, hp and torque determine towing capacity and payload.
In every case, engine power is calculated and expressed with two different numbers: horsepower and torque. Everyone knows the two numbers are related, but most aren’t clear on what they represent. We’ve got a simple explanation that should clear things up.
What is Torque?
Horsepower and torque are both measurements of engine power, but they measure that power differently. Here’s how it works:
- Imagine a human runner getting ready to race a 50-yard dash.
- When the runner pushes off from the start line, his or her leg muscles work to propel the body forward.
- The force from the runner’s muscles pushes against the ground.
- Each step increases the runner’s momentum.
The pushing force of the runner’s legs is like torque. If you put a scale between the runner’s shoe and the ground, you could measure the amount of force being applied with each step. Just as leg torque accelerates the runner, engine torque accelerates a vehicle. Here’s what you need to know about torque:
- Torque is a measure of rotating force.
- Engines create torque as they turn.
- Torque rises with engine speed to a point, then falls off again.
Remember this: More torque helps a vehicle achieve a fast 0-60 time.
What is Horsepower?
- Each step provides torque to add momentum to the runner’s body.
- If we add up all that torque delivered step-by-step over the course of the 50-yard dash, we get the total power produced by the runner.
- Horsepower is the sustained effort that gets the runner up to speed and keeps the runner moving.
Question:Why doesn’t the runner continue accelerating forever?
Answer: Because there’s a limit to how fast the athlete can move his or her legs. There’s also some drag because of gravity and wind resistance. Eventually, the runner is running as fast as possible, and drag prevents any further acceleration. It’s the same with engines. Here’s what you need to know about horsepower:
- Horsepower is torque measured over time and distance.
- Horsepower increases with engine speed, then falls off.
- Engine speed is always limited.
Remember this: Because of the math involved in calculating the values, torque and horsepower are always the same at 5,252 rpm.
Why horsepower and torque are important
When people read engine ratings, they tend to focus on horsepower because it’s a simple number that corresponds to how “fast” the vehicle will be. In fact, torque is usually more important when it comes to driving in the real world. That’s because we do so much accelerating from stoplights and stop signs. Drivers experience torque in the following ways:
- Torque is what gets the car moving from a stop.
- Torque accelerates the vehicle onto the freeway.
- Torque allows the vehicle to do more work, like pulling a trailer.
Drivers experience horsepower in these ways:
- Horsepower allows the car to climb a hill without slowing.
- To a point, faster engine speeds yield more horsepower.
- When the car downshifts to accelerate, it has more horsepower to use.
Remember this: Diesel engines produce more torque, but comparatively less horsepower.
Relating horsepower and torque to performance
Drivers expect vehicles with high torque and horsepower ratings to be fast and accelerate quickly, and that’s generally true. However, vehicle weight and aerodynamics are also important factors. Just like our imaginary runner, gravity and wind resistance affect your vehicle’s performance. Here’s what you need to know about performance:
- The lighter a vehicle is, the less torque is required to get it moving.
- Small aerodynamic vehicles like sports cars have it easier than big SUVs and trucks.
- To make more horsepower, an engine must run faster, make more torque, or both.
- You can reduce weight in your car by unloading unnecessary items.
Remember this: Performance depends on many factors, including size, weight, and engine power.
Relating horsepower and torque to fuel economy
Just like performance, you should be aware that there’s a direct relationship between torque and horsepower and a vehicle’s fuel economy. Once again, weight and aerodynamics have a profound effect on your vehicle’s efficiency. When you’re evaluating different vehicles, here’s what you need to know about fuel economy:
- Automakers have gotten really good at making efficient engines, but there’s a limit.
- Usually, higher torque and horsepower means lower fuel economy.
- Vehicle weight and aerodynamics matter a lot!
Remember this: Engine power always comes with a price. You have to burn more fuel to get more power.
What about hybrid and electric vehicles?
The most important benefits of hybrids and EVs come from their electric motors. These motors not only save fuel, they provide excellent torque. Electric motors can replace internal combustion engines, or they can add to the torque from an internal combustion engine. Here’s what you need to know about electric motors:
- Torque output stays the same at all motor speeds.
- Total power output rises uniformly with motor speed.
- Automakers are now using electric motors to boost total torque output from their engines.
Remember this: Electric vehicles are great for quick acceleration.
What about turbocharged vehicles?
One way you can make more torque and horsepower is by adding a turbocharger or supercharger to an engine. These devices force pressurized air into the engine, which also means more fuel must be burned. Putting in more air and fuel means more power is produced. Here’s what you need to know about turbocharged motors:
- Turbocharging usually adds a little torque and a lot of horsepower.
- Turbo engines usually get worse fuel economy than non-turbo engines of the same size.
- Older turbocharged engines often have weak power at low RPM.
Remember this: Turbocharged engines operate under more stress than normal engines.
Evaluating torque and horsepower when you choose a vehicle
When you’re going to buy a new or pre-owned vehicle, horsepower and torque make a big difference. However, don’t just buy the vehicle with the biggest numbers. Look at the whole package including the size and weight of the vehicle, the transmission, and fuel economy. For example, consider two vehicles:
- 2019 Ford F-350 Super Duty.
This truck weighs 7,700 pounds. The F-350 has a 6.7-liter Power Stroke turbo-diesel engine with 935 pound-feet of torque and 450 horsepower.
- 2019 Mazda Miata.
This car weighs 2,337 pounds. The Miata has a 2.0-liter engine with 181 horsepower and 151 pound-feet of torque.
The bottom line on horsepower and torque
Most people talk about vehicle engines in terms of horsepower. They’re not wrong; it’s an easy shorthand for overall performance. In terms of buying a new or used vehicle, it’s best to look at your needs before making a choice based on the engine’s rating numbers. The characteristics of torque are:
- The ability to get moving, especially with a heavy vehicle.
- Increased towing and carrying capacity.
- Improved 0-60 time.
The characteristics of horsepower are:
- Easy highway cruising.
- Great for curvy roads.
- Improved top speed
Most people will tell you they like engine power, but what they really like is a vehicle that has well-balanced torque and horsepower. The right amount of horsepower and torque is enough to accelerate quickly, but not too much. Too much power places the driver in danger of spinning the tires or losing control of the vehicle. When you think about horsepower versus torque, the most important thing to remember is that they aren’t in conflict. Torque and hp work together to give your vehicle the performance you need. Any runner could tell you that.