Torque vs. Horsepower Explained

Torque = moment = distance x force, Newton x metre (Nm), or ft x lbs, never ft/lbs.

Great explanation.

Torque is an expression of twisting force with NO REGARD FOR SPEED. It could be at 0 rpm or 10,000 rpm.
Horsepower is a more complete expression of performance, taking both torque and speed into account.

As is common when speaking of car engines, torque is usually noted AT a particular speed. This is in fact all we need to compute HP, but the math is simply not completed. We could just as easily say that X engine makes 360 hp at 3500 rpm (its torque peak) and 500 hp at 6250 rpm (its hp peak). Graphing this curve really tells us a lot.

We can double HP by either doubling torque OR by doubling the rpm at which the same torque is produced. Or more realistically, by increasing BOTH factors to a lesser degree.

Assuming proper gearing, the engine with more horsepower will ultimately do work more quickly. OTOH, most of us don't operate street cars at their HP peak very often. It is unpleasant (to police at least) and hard on the engine. Low rpm and part throttle torque is useful in everyday cars because they spend so much of their time in that range.

A lb isn't a measure of force. It should be lbf - the force of 1lb under gravitational acceleration (a pedant speaks)

Best video i've seen on this particular topic. Thanks

Lets start with the basics

Force = mass x acceleration
Torque = Force x Distance

Work = Force x Distance

Power = Work ÷ Time

THERE U HAVE IT.

Horse power is how fast you’ll hit the wall

Torque is how far you’ll move it

Never ceases to amaze me how many people get this wrong. Torque is measured in lb-ft not ft-lbs. Ft-lbs is a measure of energy. T=FxR, F for force in lbs and R for radius in ft... lb-ft. Sorry, I don´t want to be ´that guy´ but this issue grinds my gears, so to speak.

I am glad that i came across this video. Out of all the multiple vids, i found this one to be the simplest to understand. Thank you!

Perfect

Great work done here video quality is 11/10

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Great explanation now i finaly understand !

I understand. But at the same time I don't.
:-))
Torque is the power used by piston to push on that rotating shaft. But... HP is how frequent a force is applied. But, then again, shouldn't it also matter against what force the engine works? The weight of the engine itself plus the car, the angle of the road etc.

"I'm going to make it easy on my American viewers and use Imperial units.... anyway here's my spanner"

That’s the best explanation I’ve ever come across. The Narration and the visual aid provided a great way of understanding the whole process. Thank you very much.

perfect!

So for an SUV(bmw x4), which weights 2 tons:
diesel has 400nm 200 hp
petrol has 350nm and 262hp

What I understand from torque/nm is that if I put more weight on a petrol(5 people with luggage), the petrol will struggle and won't be that fast? Where diesel will not rev that much and will take it slow and handle a lot of weight.

I mean you see the specs above, I'm a bit confused what are the pro and cons for that, both engines are 2 litre engines. I'm new to car concepts

Let me ask a question - does torque affect fuel consumption? If in my engine at 1750 rpm is the max torque (200 nm), and at 2500 it’s 150 nm, it means that driving at 1750 will consume less fuel than on 2500 rpm?

how can torque increase in the graph if the length of the piston and crank length remains the same?

how can torque increase in the graph if the length of the piston and crank length remains the same?

There are lot of videos on internet, but you made it really easy... I'm comparing with big channels like Donute Media.. your articulation is too good!

woah so that's why electric freight locomotives seem to move smoother and faster than diesel ones specially watching them electric locomotives seem to move double decked cars more easily than the diesel one could even if they have same tonnage

Hopefully we should keep electric cars away from bad drivers, with that instant torque and high power output...

Helped, thanks

Imperial units are stupid. Use metrics!

Incredible. Wish i could buy u a drink. Thanks. Torque and its formula is as eady as 2+2, but understanding it related to the engine gave me problems. 10 vids in, I found the answer thanks so much

I have watched more videos explaining this subject than I care to admit, and finally, this is the video where it finally made sense.
Thank you so, so, so much for this!

Well explained 👏👏👏

It is a common misconception to believe that a longer stroke generates higher torque. The complete physics and thermodynamics of it all are quite complex, but in general terms, for a given displacement, the longer stroke is offset by the smaller piston area on which the combustion gases apply pressure, which results in less force being applied. Truck engine make more torque because they are big: there is no substitute for displacement.

Also, a 300hp engine will be able to move the same heavy load up a hill at the exact same speed, be it a 8000rpm sports car engine or a big diesel truck engine, it's all in the gearing. Truck engines are "tuned for torque" simply for durability and fuel economy reasons. By being able to generate the desired power levels at low RPM, they can last way longer and consume less fuel in the process.

Ninja zx25r 4 cylinder = 51hp and 22.9 Nm and Ninja 400 2 cylinder = 45 hp and 38 Nm

More piston = more hp and less piston = more torque

The thing i wanna ask is how vehicles like trucks produce more torque than horsepower. I know that trucks have big engines because of longer strokes and use diesel because it produces more torque. But do things Like what the piston is made of or how heavy the piston is or the combustion power of the fuel affect torque in any way?

This video cleared my confusion of torque and hp inside a combustion engine, I was so lost. Thank you very much.

It does not explain why the torque decreases yet the total power increases this should be explained. Engine friction increases which decreases torque with higher revs, but despite less torque the extra revolutions still give more power. Example less power per engine revolution but twice as many revolutions still give more usable power in a minute. Engine design and breathing size all alter the torque curve

Great. Thank you Apple & Onion.

Horsepower at the engine is more important than torque at the engine. If you have horsepower at the engine, you can always use gearing (torque multiplication) to increase the torque. If all you have is torque, you CANNOT get extra power by modifying the gearing. Ever. That's physics.

eh?

Good use of graphs to explain that hp and torque aren't constant when it comes to motors.

Best explanation I've heard so far thanks!

how did you do it can you share with me , thank you

I swear, out of all the videos that explain power and torque (which have many more views than this video) this one is the most clearly explained and complete. This video was really helpful. I'm glad I came across this video.

power (watt) = torque (Newton meter) * angular speed (radian / s = 2 * pi * rpm / 60).
torque is a parameter of power. so do you need torque or power? answer both my general.
the interest of the couple only appears on the acceleration aspect
inertia * acceleration = motor torque - resistant torque (simplified presentation). If you want good acceleration, decrease the inertias (moving masses) and increase the engine torque, the resistive torque being fixed by the tires, aerodynamics and the slope of the road.
if you want to go fast you need power to obtain equal engine torque = resistant torque at cruising speed (at high speed the aerodynamic effects are enormous)
as explained, electric motors have a much more favorable torque versus speed curve than thermal motors.

How is horsepower increased or decreased? I mean how to design an engine for horsepower?