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The question ‘what is horsepower’ is one that appears on Google quite a lot and although it’s a fairly easy question to answer, the more complicated act of understanding the difference between torque and horsepower is something that we’re going to take a look at today.
What is the difference between torque and horsepower?
There’s an easy way to differentiate torque and horsepower. When it comes to an accident, the horsepower is how fast you hit the wall and the torque is how far you move it. If you crash on a 300 lb motorcycle, the wall isn’t going to move much, but when you’re in a 75,000 lb truck the wall is going to get shoved a couple hundred feet. These are two very different types of work.
Irrelevant of the differences between these two engine factors, generally speaking the bigger the number the better but the relationship is more significant than that. You can’t have one without the other. When it comes to assessing the capabilities of an engine, horsepower and torque are the basis of what it can do.
Used in the majority of automotive advertising, consumers don’t often realize the significance of the figures they’re given. Although a vehicle may produce a lot of torque, the more horsepower available, the more potential torque is available.
I guess the easiest way to remember the relationship is to think of horsepower and torque like siblings. They are very similar but have less in common than you might think.
Let’s get really textbook on this and define what each term means, considering we’re going to talk a lot about them.
Energy is the collective power created from the using and combining of physical elements.
When force acts over some distance, the result is work. Generally speaking, this is measured in foot-pounds, or newton-meters.
Torque is the rotating force found in an engine and is used to measure the engines ability to perform work. Although torque is similar to work, it varies slightly because it is acting in a certain direction.
Power is essentially how fast this work can be accomplished and is often referred to as horsepower.
What is horsepower?
Horsepower is the measure of power. At least that’s the simplified version of it and the main thing to remember. Horsepower is power. I guess the clue is in the name. Working out what that actually means could be a little difficult, especially when every car manufacturer has a different way of measuring power: horsepower, brake-horsepower, kilowatts are just a few.
Essentially when it comes to measuring power, we’re trying to find out how fast (or far) the car can force itself.
If we go back in time to around 1750, we stumble across the ingenious James Watt. After unsuccessfully trying to sell a ‘rotative steam engine’ that could easily outpace the horse but he didn’t have any takers, so he decided to put the power into a more understandable measurement for his potential buyers.
Using observation and a complex mathematical equation, Watt was able to determine that a single horse could push 33,000 pounds one foot in a minute. This is the power of one horse…that’s right, you guessed it, one horsepower.
Unlike our friend horsepower, torque can sometimes be the lesser understood counterpart of car specifications. If we simplify the principle, torque is the amount of work an engine can employ. If we get as bit more technical, torque is measure of force used in twisting an object, more specifically, the crankshaft.
So torque is the measurement of twisting force that’s accessible at the crankshaft at any given engine RPM.
Torque comes in two measurements. There’s the newton meters or the more old school pound feet.
The simplest equation looks like this: Torque = distance x linear force.
Say, for example, you’re tightening a wheel nut with a wrench.
The distance would be the length of the wrench.
The linear force would be the Newton force used on the wrench.
Let’s agree the wrench is 0.5m long and the force is 50 Newtons. Multiplying them together gives us the Newton meters answer:
50 (N) x 0.5 (m) = 25 Nm of torque
If you prefer the imperial measurement of pound feet then we need to do some conversions.
The wrench would be 18 inches.
The linear force would be 20 lbs.
The equation stays the same, we’re just substituting the numbers:
20 (lb) x 1 ½ (ft) = 30 lb ft of torque
What’s the relationship between torque and horsepower?
These two forces, although one may often be forgotten, can’t exist without each other and work in unison to provide a powerful engine.
To calculate HP, you need another equation: HP = torque x RPM ÷ 5252
So when it comes to comparing engines, the one with the higher torque will always have the higher hp too.
What are your thoughts on the discussion today? Can you provide your own analogy or story to help remembering the difference between the two? Is this something you’ve always known or something you’ve struggled to get to grips with? Share your thoughts and comments below.