Contrary to popular belief, the terms horsepower and torque are not interchangeable. While engine speed or RPM, horsepower and torque all work in conjunction with one another, they are in fact very different. When you are looking to modify your vehicle to make more power, it would be a good idea to understand horsepower vs torque. This is a precursor before taking your vehicle into a chassis dyno.
Once you understand the differences between horsepower vs torque, you’ll be better equipped to modify your vehicle further. Here’s a few informational key points to understanding horsepower vs torque better.
Recognizing the difference between horsepower vs torque
Although the differences between horsepower vs torque are vast, you can’t have one without the other. Torque is also known as force or kinetic energy that turns your engine. Because this value works independently of your engine, it’s possible to have torque when your engine is at 0 rpm or zero engine speed. This can happen in a steam engine or one driven by an electric motor.
One of the major differences between horsepower vs torque is that the nature of torque does not change, regardless of engine speed. This means that no matter what RPM your gas engine is operating at, the nature of the torque remains the same. However as engine speed rises, the torque plays a bigger role in determining the horsepower of your engine. To understand the basic equation behind horsepower vs torque, check out the calculation below;
Horsepower = Torque x RPM
From this basic equation you will see that engine speed and torque work in conjunction with one another to produce horsepower. In simplest of terms, horsepower is the measurement of work being done, or how much action is being performed. To understand how these two work, try to understand a hypothetical engine that’s running between 1000 RPM and 7000 RPM.
Let’s say that the hypothetical engine generates 100 ft lbs of torque at 1000 RPM, and 300 ft lbs of torque at 4000 RPM, and 500 ft lbs of torque at 7000 RPM. While torque is linear and produced at a flat rate in this example, horsepower is very different. Based on the torque and increased engine speed, more horsepower can be produced.
This is how F1 engineers crank out well over 700 horsepower from a 3.0 liter engine spinning at 16,000 RPM. The flow rate of your engine should be easy to understand using the basic principles of airflow. It’s safe to say that any engine operating at 4000 RPM would flow almost twice as much air than at 2000 RPM. This doesn’t take torque into account, because the size of your engine will play a huge role there.
It’s safe to assume then using this hypothetical engine to prove horsepower vs torque, a 4.0 liter engine at 3000rpm would flow much more than a 2.0 liter engine at 3000rpm. This is why so many people believe there is no real replacement for displacement. So when modifying your vehicle, you need to either increase airflow, displacement or engine speed to produce more output.
Unlike our hypothetical engine, torque is not produced in a linear fashion most of the time. Combustion engines produce a sweet range of horsepower and torque, and each engine will vary depending on volumetric efficiency. Because each engine is so different, you’ll need to understand at what engine speed your engine produces peak flowing capability.
Want to learn more about horsepower vs torque? Subscribe to My Pro Street today to get all the latest in tech tips and How To Guides.