“Look at this! The Corvette Z06 engine makes 500 horsepower and 475 foot-pounds of torque,” exclaims Sarah.
“Is that good?” asks Matt.
Do you know what horsepower and torque are? These terms come from physics, and are used a lot when talking about cars and trucks. Here’s what these terms mean for internal combustion engines.
First, let’s talk about horsepower. Horsepower was originally used to describe how much work early engines could do relative to how much work a horse could do. But the 500-horsepower Corvette engine doesn’t do the same thing as 500 horses.
Horsepower is equal to 33,000 foot-pounds of work per minute. Stated another way, one unit of horsepower is what it takes to lift 33,000 pounds the distance of one foot in one minute. James Watt, the inventor of the most successful steam engine, defined the term with this formula.
Now, let’s talk about torque. For engines, it is easiest to describe torque as a twisting or turning force. The engine’s job is to turn the wheels of a car or truck, which requires the turning motion of torque. Powered by the engine’s torque, the wheels turn to start moving a vehicle that is stopped. So, in order to start moving a car or truck from a stop, an engine needs torque.
Horsepower and torque work together to make vehicles move. Some vehicles have greater horsepower than others, and some have more torque. Others have lots of both. You may hear about horsepower in commercials for performance cars, while ads for trucks will focus more on torque. That’s because higher torque is useful for tasks like towing boats or trailers. More torque is required to start a heavier vehicle from a stop than a lighter vehicle. Greater horsepower is usually used to make a vehicle go faster than another vehicle.
The formula for calculating the horsepower of an internal combustion engine is:
Horsepower = Torque x RPM / 5252
RPM stands for “revolutions per minute,” or how many times the four-stroke cycle is completed in one minute. So, one cylinder in an engine goes through the four-stroke cycle and produces a certain amount of torque. Multiply that number by the number of cylinders to get the total torque, and then complete the equation.