Horsepower vs Torque – A Simple Explanation

# Horsepower vs Torque – A Simple Explanation

Hello everyone and welcome. In this video we’re going to be talking about the difference between torque and horsepower.
And we’re not going to be using any strange analogies and very minimal math; just talking about theory and keeping it easy to understand.
So we’ll start things off with torque.
Torque is simply a force applied at a distance.
You can think of it as a twisting force. So if you’re trying to tighten something down using a wrench,
You apply a force, you press down at a distance, the length of that wrench, and that supplies a torque at whatever you’re tightening.
Same idea with a socket wrench. So if you’re tightening down a bolt you apply a force at a distance,
And that supplies a torque to that bolt to fasten down that bolt.
Now the same thing is happening with your engine.
So combustion within your cylinder is what’s supplying the force pressing this piston down, and then that piston is pressing down on a crankshaft.
So as you can see, you’ve got your force pressing down,
You’ve got your distance where it’s pressing on the crankshaft, the axis of rotation is the center here the piston is pressing offset from that center so at a specific distance and
Combined that gives you your engine torque, force pressing down at a specific distance that gives you a twisting force
That’s the torque that your engine is making now torque can be manipulated very easily
By using gears or by using leverage for example
So this will supply you know with the maximum amount of force I can supply to it a certain amount of torque
But then if I were to use something much longer
Now I have more leverage I can press at a greater distance and since torque is force multiplied by distance
The torque here is going to be significantly greater
Okay, so what is power and how do these two relate? Well, power is the rate at which work is done
So what does that mean? Well if I move this car from here to here. I’ve done a certain amount of work
I’ve moved this from here to here, now if I do it very slowly
it doesn’t require much power. if I do it very quickly it requires more power
Now ultimately I’m accomplishing the same thing
I’m moving the car from here to here, but I’m doing it faster
The rate of work is greater therefore
It takes more power so more power going quickly than going slowly
So power ultimately is what gives you speed, what gives you acceleration now the two are connected so in in our context
Here looking at our engine. We have torque as a force pressing down acting at a distance
Well how fast that’s happening is our power so that’s our rpm. So horsepower is torque multiplied by rpm
So how often this interaction is occurring…
And so how fast is this spinning while we’re still getting that consistent force acting on the piston so the faster it spins
Supplying that same amount of force at that same distance the more power we’re going to make
Okay, so how about an example to help explain things further?
Let’s say we have two different vehicles that are exactly the same. Now, I know these look different, but we’re just going to pretend
They’re exactly the same nothing about them is different except this one has 200 horsepower and a hundred pound feet of torque
Those are the peak numbers. This one has 200 pound feet of torque and a hundred horsepower so half the power
Twice the torque this one has twice the power half the torque
Which one is going to accelerate faster assuming both of them have the same mass?
And everything else about them is equal
Well the one with more power is always going to be quicker because that is the rate at which work is done
That’s how quickly it can accomplish work move something from one place to another it can move it faster
Now this one has more torque, great
But as we know torque can be manipulated through gearing so gears act just like leverage
So while this doesn’t have as much torque as this
If I’m applying torque to something I – my power doesn’t change, how strong I am doesn’t change
But I can use leverage just like cars can use gears to make more torque so this car with twice the power
But half the torque can use gears to accelerate faster, so it can use a longer
You know leverage arm a greater a more aggressive gear ratio
So that it can put that power down and ultimately because it makes more power it can do more work more quickly
It will be the faster car.
Okay so now let’s talk about horsepower and torque curves because when a manufacturer gives you a horsepower and a torque figure
They’re just giving you the peak figure for each of those
They’re not giving you, you know the amount of torque that that produces across all of the engine rpm range
And so if you look at a torque curve, it’ll have some peak along that curve with respect to rpm
so that’s the engine rpm in which the force pressing down on the piston is at its greatest so that’s peak torque
and what that means if you stay within a set gear, if you’re in one gear
let’s say you’re in third gear, you will feel the – the force pressing you against your seat will be the greatest at peak torque now
That’s assuming you’re staying at a constant gear ratio
You’re staying within one gear
So now if you look at the horse power curve overlaid over that torque curve
At some point, peak horsepower will occur
And that’s when the engine is doing the most amount of work it can do and so at this point
You may think okay if I want to accelerate fastest
I need to be at peak torque, so you want to be at that peak spot
Well, that’s only true for a set gear and that’s only within that gear if you can manipulate the gear ratio
Let’s say peak torque is right here
But peak power is over here, later in the RPM range you can sacrifice torque
But get a more aggressive gear ratio, and ultimately accelerate more quickly by accelerating at peak power
So why is that well that’s because you’re multiplying your torque by the gear ratio
So you have peak torque multiplied by a lower gear ratio versus a lower torque
But multiplied by a significantly higher gear ratio at peak horsepower
That will give you your peak acceleration
So for example CVT transmissions
Which can adjust the gear ratio constantly
If they adjust that gear ratio to maintain the engine at peak horsepower
They will accelerate the fastest rather than if you were to manually shift gears, or have an automatic transmission
Which shifts between gears and you’ll feel that peak sensation
that peak force against the seat at peak torque as you cross over it, but the actual true amount of peak acceleration
That’s possible with that engine would be if you manipulated gearing if you
Manipulated leverage to allow you to be at the highest horsepower
Level with the most aggressive gear ratio possible
so a quick review, torque is simply a force acting at a distance
Horsepower is how quickly you can accomplish work, now both of them require each other
They’re a function of each other horsepower is torque multiplied by rpm, so you’ve got a specific torque
and then you spin the engine at a certain speed, that will give you power
And so ultimately they are you know they require one another you can’t have horsepower without torque
But the most important figure if you’re looking at “how fast will a car be able to accelerate?”
“What will its top speed be?” that comes down to power because that’s telling you how quickly?
Can you accomplish a certain amount of work
So hopefully this has cleared things up; the differences between torque and horsepower
If you have any questions or comments, feel free to leave them below. Thanks for watching