Of of the most constant struggles of my life has certainly been to *actually* understand the relationship and functions of torque and horsepower (along with its cousins: watts, amps and voltage… but that’s for another time). When you modify car components to increase power, the evaluation almost always revolves around how acceleration within a specific measurement (i.e. distance) has been affected.

Here’s are the fundamentals:

Horsepower is the total power output of an engine, while

torquemeasures the “turning/torquing ability” of the engine. Practically,torqueis a better measurement of how quickly yourcarwill accelerate, while horsepower (relative to weight) is a better measure of yourcar’stop speed

This is one of the best explanations of torque and horsepower that I’ve come across:

If you watched the video now it all makes sense 😭😂

I even decided to leave a comment:

This is a great explanation. Although horsepower is Torque x RPM ÷ 5252 (which is the magical point where torque and horsepower lines cross on graph). Also in the car racing example there were certain parameters left out (i.e. the race’s distance). It

ispossible that the car with less horsepower and more torque could actually win a very short race. The discussion about gearing in this example is confusing because gearingcanalter torque. All things being equal the one with more power willeventuallybe quicker.

**Torque** is *force* x *distance*

**Horsepower** is *force* x *distance* x *RPM / constant *

so, more specifically,

**Horsepower** = *torque* X *RMP* / *5252* (this is the point where torque and horsepower lines cross on a graph).

I made my comment above because I felt the video slightly misrepresented things @ 3:15. It’s really not a big deal but it could be slightly confusing for those of us truly looking for the light.

Below I’ve also posted an interesting comment made on this video by Martyn M. *I have edited parts of the story for brevity and clarity, but the content is intact. *

It is measured in either Newton Metres, or Lbs Feet. In this example we will just keep things simple. Think of torque as brute strength.Torque is a turning force.

Horse Power is a method of measuring how much work is done in a given time.You need torque, multiplied by how many revolutions per minute, that torque is applied, to work out how much horsepower is achieved in a set time.

This is the way I think of it…

There are two piles of bricks, one hundred in each pile, and they need moving up a fairly steep hill on a building site.

A muscle man and a marathon runner challenge each other to a race, to see who can move a pile of the bricks the fastest.

The chap with a lot of muscle and strength is big and immensely strong but heavy and quite slow ( (we will think of it as having lots of torque). He is quite capable of scooping up a whole load of bricks and carrying them up the hill. He might carry 20 bricks at once and slowly walk (at low revs) up the hill. He could move all the bricks in 5 trips and take 10 minutes.

The seriously fit runner, who is light and fast on his feet might only carry 5 bricks and sprints up and down the hill. He has a low amount of muscle (or torque) but his legs can run (or perform revolutions) at a much faster rate. It takes the runner 20 trips to move the bricks. Also in 10 minutes

Now if they both complete the task in the same time, then they have both done equal amounts of WORK (which can be measured in Horsepower or Kilowatts) then it’s a draw.

However, if the muscle man could carry 25 bricks per trip, at the same pace, he completes the task in 4 trips, and in just 8 mins. He will have put out more horsepower. He carries bricks at a slow pace compared to the runner, but by applying more torque, each rpm is doing more work. Then it’s just a case of multiplying the two together. Torque x RPMs.

However, the runner, still only carrying 5 bricks, refuses to be beaten. He hasn’t got the strength (or torque) to carry more than 5 bricks, but he can pick up the pace so he runs faster. He finishes the task in 7 mins. His body, although weaker at lifting, has now worked harder, because his low amount of torque, could be multiplied by very high revs.

Keep this example in mind and think of your car engine. Horsepower is simply a way of measuring work done in a given time. It is not a unit of force, or a measure of how fast it can travel. The ability of an engine to provide power is achieved either by applying large amounts of torque at low revs, or applying lower amounts of torque at high revs.

The amount of gratitude and praise for this post is surprising because ultimately I think it misrepresents the relationship of torque and horsepower (unintentionally). Based on this story, both machines (brick movers) accomplish the same amount of work in the same time period. But I think he confuses the issue at some point during his explanation and arrives at the conclusion that both the muscle man and the runner have accomplished the same amount of work in the same amount of time and so their horsepower is equal. It is *not*. In this example the work being done has been erroneously broken into impossible parts.

The power an engine produces is called

horsepower. In mathematical terms, onehorsepoweris the power needed to move 550 pounds one foot in one second, or the power needed to move 33,000 pounds one foot in one minute.

A car cannot be moved in 100 pieces arriving at it’s ultimate destination over any period of trips. Am I thinking about this incorrectly? I’d value any insights into this matter- there’s just something here that I can’t completely wrap my head around…

Another question I’ve been thinking about is this: When you alter the gearing in vehicle you can change the torque but you cannot change the horsepower. Why is this?

Let’s say your vehicle makes 600 ft lbs of torque @ 7500 rpms. Your horsepower output would be 600 x 7500 / 5252 (the point where torque and horsepower lines cross on a graph). This gives you around 856 HP. You can change the gearing on your car to give you more lower end torque. Let’s say you make an adjustment that gives you 650 ft lbs @ 6900 RPMS. How much horsepower do you have? Yes- the same. The theory here is that you’ll be faster inside of a certain window (in this case up to a certain speed you’ll be quicker).

All things being equal, one could probably make a simplistic assessment that horsepower is the *definitive* measurement of power. If you’re obsessed with top speed then *that* is the number that matters. If all you care about is how quick your car feels off the line then you’ll need more low end torque (and this, of course, is why measurement of peak output don’t paint the whole picture).

An engine only produces peak horsepower and torque at certain ranges. You can take a snapshot of the car’s maximum output but this doesn’t always give you the true picture of a car’s power over the *entire* output range (I’m probably misusing the term “power” here…).

I think this is why, in theory, a car purported to have “600 hp & 500 lbs of torque” *could* be “beaten” (in a shorter race and absent any considerations of weight or aerodynamics) by a car with “550 hp and 480 lbs of torque.” This is why people take their cars to the the track and put them on dynometers; You need a physical application of the engine’s power to really appreciate their real world performance.

And speaking of real world performance (I alluded to it above) but there are no many more factors than just horsepower and torque to take into account when you’re trying to make assessments. A car’s weight, drag and even friction could play a part in a car losing to a less powerful competitor.

Anyway… quite a rabbit hole. The amount of information about horsepower and torque online is truly overwhelming and the debate about what’s more important and the misunderstandings about their relationships will probably continue forever (they are both important). As for me- I’m just going to live my life by the stopwatch. No one can argue about time*.

*They can argue about *who* robbed them, *why* they were robbed, *what* went wrong, etc, but they cannot argue about how long a particular race event took (except in the absence of any accurate timing device). Ah… who am I kidding. Time is relative, right?