Whats the difference between Torque and Horsepower

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Horsepower is how fast you hit the wall. Torque is how far you take it with you.

Hope that helps!
 
^Nice example!

So if they were animals, horsepower would be a cheetah and torque would be a rhino, am I right?
 
AlexGTV
^Nice example!

So if they were animals, horsepower would be a cheetah and torque would be a rhino, am I right?
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No.

A cheetah and a rhino both perform work in a given time, ie; they move around a bit (horsepower...erm...cheetah power?).

If said cheetah, or any random feral animal for the matter, butted its head against a wall and pushed w/o moving or compressing anything; then they'd be providing force, "torque", but not really performing any work, "horsepower".

The best example I can think of is removing a bolt/nut/lug that's rusted on. You tug and tug, all while applying torque, but nothing happens. You use a bigger wrench, which multiplies your torque, and blammo; the whatever is broken free.

Torque is measures as ft/lbs or n/m or whatever. Basically, it's a weight and a distance. If you attached the wrench to the bolt in the above example w/a wrench that's 6" long and you weigh 200lbs...you're applying 100 ft/lbs of torque to the nut. If you use a 1' long wrench, 200 ft/lbs. 2' wrench, 400 ft/lbs. This is torque multiplication, which is commonly referred to as leverage.

But what happens when the bolt moves? A-ha! There's another variable added; movement...or more precisely...distance.

The twisting force needed to move an object from 1 point to another is no longer a measurement of force but one of work performed. Comparing torque to horsepower is really apples to orangutans.

Put simply; torque doesn't do anything...it's just a number. When that torque actually does something...it mathematically disappears and becomes horsepower. Power charts showing tq/hp are very misleading IMO as torque is graphed only to show where the HP numbers are calculated from. You cannot isolate torque from HP once something is set in motion. To do so would be like saying 2+3*2=5. You cannot ignore the * or anything else in the equation just b/c you feel like it and proclaim the answer is correct.

In the world of cars w/multiple speed transmissions; horsepower is everything.
 
Torque is a force causing rotational acceleration. Work is the distance over which that force is applied. Power is the amount of time it took to perform that work.

So if you imagine something with massive torque but low power, it would apply huge rotational force to move a certain distance - but take a long time to cover that distance. Nothing could stop it from twisting, but it would take a very long time to reach a high rotational velocity. Try to imagine the barrel of a cement truck. It twists slowly, but good luck trying to stop it.

If you imagine something with low torque but massive power, it would apply a tiny rotational acceleration over a certain distance - but would take a short time to cover that distance. You could stop it from twisting, but if you didn't it would twist very quickly. Imagine an fan that you can stop with your finger. Let it go and it covers a lot of ground.

If you have a drag race between two vehicles with the same weight, but one has high torque and the other has high horsepower, the one with the torque would likely jump out into an early lead before the one with the horsepower reeled it in and passed. Which vehicle won would depend on how long the drag race is.

The concept of gearing is really what confuses all of this, because the larger the diameter of the gear the greater the torque from the engine, but the greater the distance that needs to be traveled to move the wheels - and as such, the same power is used to achieve greater torque at the cost of speed. As you move to smaller gears, torque is given up to achieve greater speed at a set amount of power. This is all further complicated by the fact that force from the engine changes with rotational speed.

Besides gearing, the whole thing is harder to visualize when dealing with rotation. Consider the job of simply picking something up. To translate from rotational motion into straight-line motion, interchange torque with force and imagine lifting a box. Being able to lift the box a millimeter requires the same amount of force as being able to lift the box a mile. The amount of work you put into lifting the box is the amount of force you apply to lifting the box multiplied by the distance over which you lift the box. You put in twice as much work using the same force to lift the box twice as high. The amount of power you use to lift the box is determined by how long it takes you to apply the force to lift the box as high as you lift it.
 
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Some nice examples here. Gears/power/torque are kind of my hobby along with cars and mototrbikes. I wish GT5 would include thrust curves along with dyno graphs.

A Dyno cuve shows us what an engine is capable of, but include gearing and things become more interesting. A dyno graph can only tell us one part of the story, but it cant give you and exact figure of forward thrust at say 46.5 mph in 3rd gear, or 121mph in 4th, but a Thrust curve can. Having thrust curves makes comparing vehicles performance much more realistic and fun.

I own a 1000cc 130bhp 80 lbs/ft of torque motorcycle. With its current gearing it has a peak thrust in 6th gear of just over 300lbs. The average 600cc sports bike equals that figure in 6th gear with almost half the peak torque. 45lbs/ft. Reason for this is that the average (new) 600cc superbike bike revs 5000rpm higher than my bike, 10,000rpm vs 15,000rpm) so can have a 6th gear ratio almost half the size of my bike yet still hit the same theoretical top speed.

A fit human on a pushbike can produce about 1bhp but a huge amount of torque. If humans could spin there legs, anywhere near as fast as a typical petrol engine, we would not need engines in some cases ;-) Its not our torque limiting us, but our ability to rev. 30-120rpm for any kind of period is typical. As we can't rev/spin our legs high enough, rather than using very low gears to go fast using high rpm's (Pedal rotations), we use larger gearing, and use our torque to push those gears so we can achive our cruising/top speeds more efficiently.
 
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In a public bus I once asked the driver if the engine had huge horsepower (my bad), and to my surprise he answered no. So it surely must have a lot of torque or how else can it carry 50 people?
 
It was almost certainly a diesel. Diesels tend to make huge torque numbers but lower horsepower, partly due to their inherently lower redline.
 
I'm getting tired of all the automotive journalists that always refer to the "torque" when testing cars, as though the torque number alone could tell you anything about a cars performance.

The torque isn't going to move an object alone.
Example: I'm on my mountainbike, on the highest (fastest) gear. From a standstill, I can push on the pedal with, let's say 10Nm (7.5 lbft), but the bike won't move, because I have 0 rpm's. It's too heavy for me to move with that little amount of power.

The above example is to show that torque alone isn't going to move your bike/car.
But once you add revs to the torque, you start moving.
Initially, it's quite heavy to pedal, and because it's so heavy I can't pedal that fast (not many revs).. But I still apply 10Nm of torque to the pedals all the time.
As speed build up (remember that in this example, my torque on the pedals is constant), it's getting easier and easier to pedal faster and faster. Eventually, the revs (as in how fast I pedal) increase so much that I reach the maximum of revs that I'm capable of = Bike reach top speed.

In the above scenario, I've applied the exact same amount of torque all the way from starting the bike from 0, all the way to top speed.

How is this possible?
Same torque, but speed over a range from minimum to maximum?
The answer is: Revolutions per minute.

To calculate bhp from torque, you need to ose this formula:
[(lbft * revs) / 5,252] = Effect (P) or in this case, BHP.

Let's say that your engine produces 300 lb-ft @ 3000 rpm.. Simply put in the numbers in the formula:
[(300 * 3000) / 5,252) = 171 BHP
And the same torque once again, but at twice the revs:
[(300 * 6000) / 5,252) = 342 BHP
So from the above example, we can clearly see that Power/Effect/BHP (What moves an object) increases as revs build up.

Here's 2 widely separated examples:
F1 engine:
Volume: 2,4 liters
300 lbft @ 15000 rpm
(300 * 15000) / 5,252) = 856 BHP

Diesel machine engine:
Volume: 24 liters
3000 lbft @ 1500 rpm
(3000 * 1500) / 5,252) = 856 BHP

As you can see, both engines produce the same amount of BHP.
Both engines are equally strong.
(I know that there's practicality issues with a 2,4 liter F1 enigne pulling the diesle machines load, but it's not the engines power that puts a stop to that. It's the high gearing which does'nt belong to my example. My example is only aimed to bring some light to the BHP/torque debate. We only need to compare the engines to prove this. Other practicallity issues are not taken in to consideration. Just to be clear, it's entirely possible for the F1 engine to pull the diesle machines load, as long as it's fitted with a gearbox that fit the job.)

So with the above examples in mind, what do you want to know when looking at 2 cars.. Do you want to know how much torque it has, or how much bhp it has (ofc from a performance perspective)?

Car A: You'll get 500 lbft in this baby
Car B: You'll get 500 BHP in this one

We assume that both these cars are similar and looks like your ordinarly car in general (i.e, a pickup, weight around 2000 kg)
So, which one is the fastest?

Well, it's hard to tell, right?

If I put it this way:
Car C: 500 lbft
Car D: 400 lbft

Which one is the fastest?

Or, if I put it this way:
Car E: 500 bhp
Car F: 400 bhp

What I'm trying to get to, is that torque alone doesn't say anything. BHP does. Why? Because BHP ((P) or Effect or power) is what moves an object.


We can have 2 similar cars as the last example:
Car A:
1000 lbft (max) @ 2500 rpm
500 lbft @ 5000 rpm

Car B:
500 lbft @ 2500 rpm
1000 lbft (max) @ 5000 rpm

So, both car have the same max torque (1000 lbft), but which one will be faster? Or will they be equally fast?
Well, as I said, torque alone will not tell you anything about an engines performance, BHP will.

Car A:
[(1000 * 2500) / 5,252) = 476 BHP @ 2500 rpm
[(500 * 5000) / 5,252) = 476 BHP @ 5000 rpm
A flat powerband.. Peak BHP: 476

Car B:
[(500 * 2500) / 5,252) = 238 BHP @ 2500 rpm
[(1000 * 5000) / 5,252) = 952 BHP @ 5000 rpm
A more narrow powerband. Peak BHP: 952

So, given that both cars are fitted with a gearbox that suit the powerband, Car B is the faster car by miles. (double the power compared to Car A)

Famous quotes that couldn't be more wrong:
"There's no substitute for cubic inches"
Yes, their is: RPM's

"Horsepower sells cars, torque wins races"
Wrong. What makes your car cross the finish line is the power (Effect (P) or BHP) it produce.
 
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If horsepower sells cars, and torque wins races is wrong, then why do teams at Le Mans complained about the torque monsters the Audi lmps were?

Some of the praise the Audi lmp drivers gave were for their torque.

Low speed torquey engines are also more usable compared to a high speed power engine.
 
52361-lance-armstrong.jpg


Why wait to go through all those gears when you can start in 6th and haul ass too?

ForstemannTR31_OG812-077.jpg


That's torque.
 
sumbrownkid
Low speed torquey engines are also more usable compared to a high speed power engine.
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Not to mention much more reliable. I doubt a low a high RPM, low torque F1 engine could hold up in a 12 hour endurance race against a high torque, low RPM LMP engine. So in a way, torque can win races. But conversely, an LMP car will never beat an F1 car in a short race.
 
Denilson
I'm getting tyred of all automotive journalists that always refere to the "torque" when testing cars as in that the torque number alone could tell you anything about a cars performance.
Click to expand...

As a tiresome automotive journalist I can confirm we say things like that - often combined with a rev range over which the engine delivers peak torque - because it gives readers a good indication of how little or how hard you have to work an engine to get you down the road. It's about flexibility.

Your own example of the F1 car and diesel tractor illustrates this perfectly. Theoretically, there's nothing stopping the F1 car pulling the tractor's load. But it has to work much, much harder to do so.

A throwaway line on a torque figure per rpm number gives the reader a fairly good impression of whether the car is one you need to rev the nuts off to get anywhere or simply rumble around at tickover everywhere.

If the impression you're getting is that torque is automatically being used as a term to describe how fast something can go, then you're probably not getting to the crux of the article. Or reading the wrong articles.

Alternatively, if it's annoying you that much, then you might just need to get out more.
 
Denilson
Here's 2 widely separated examples:
F1 engine:
Volume: 2,4 liters
300 lbft @ 15000 rpm
[(300 * 15000) / 5,252) = 856 BHP

Diesel machine engine:
Volume: 24 liters
3000 lbft @ 1500 rpm
[(3000 * 1500) / 5,252) = 856 BHP
Click to expand...
And having to have to rev up to 15,000 RPM all the darn time isn't a downside of the engine itself?

Damn, I for one would be annoyed if I had to rev the engine in a car to death to get somewhere, let alone haul a wee bit of stuff around. Also, I'd think that always revving the engine up that high won't be very economical, either.
 
My post got deleted after the merge, so here goes :


Torque = acceleration/the rate of momentum delivery to the wheels to get it rolling and increase speed
HP = top speed/the ability to overcome drag due to weight, friction and air resistance once the wheel is rolling

Engine power/torque curve decides at what speed the car will excel in. Moderately low rpm peak torque/high rpm peak HP means the best of both world ( wide power band ). Then the issue with reliability, high rpm peak torque/HP means more wear, and we can't have an engine with peak torque and HP at the same rpm point, it would be pointless no matter where the rpm point is ( high or low ).

I think the best would be peak torque at half the rpm point of peak HP, you don't need to rev much to get off the line quickly or exiting a low/med speed corner, while still getting decent top speed with high rpm peak HP. Of course gearing plays a huge part as well.

Oh, don't forget the flat peak torque curve from mid to high rpm while having high rpm peak HP that holds until the red line, that would be the best engine to have. I've read somewhere some high displacement V8 and inline 6 could actually have it with clever AR ratio turbocharger choice, internal upgrades and tuning.
 
sumbrownkid
If horsepower sells cars, and torque wins races is wrong, then why do teams at Le Mans complained about the torque monsters the Audi lmps were?

Some of the praise the Audi lmp drivers gave were for their torque.

Low speed torquey engines are also more usable compared to a high speed power engine.
Click to expand...

Well, I guess you have to read my post again.
You can in theory put 1000000 lbft on a wrench, but still not beeing able to create effect (P).
Effect is what accelerate the car. Nothing else.


homeforsummer
If the impression you're getting is that torque is automatically being used as a term to describe how fast something can go, then you're probably not getting to the crux of the article. Or reading the wrong articles.

Alternatively, if it's annoying you that much, then you might just need to get out more.
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What annoys me is that many, many automotive journalist say i.e during acceleration things like: "WOW, that's the torque right there" and similar, when we all know that torque is'nt what he's experianceing. He feel the effect accelerating the car. Nothing else.

And I did'nt want to offend you in any way.

daan
of folk that just press the new thread button instead of searching.

Merged.
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Depends on how you look at it.. Either read this entire thread with all the nonsense in it.. Or have an own thread where the correct information is in tho OP under a thread headline that indicates what kind of information you can expect to find.
What I wrote is physics.
It's nothing that can be debated.
It's facts.

But sure, go ahead.. A forum/community is'nt there to share information, right?
So just hide that huge chunk of facts in page 2000000 cause it's not of any interest after all.. 👎

Luminis
And having to have to rev up to 15,000 RPM all the darn time isn't a downside of the engine itself?

Damn, I for one would be annoyed if I had to rev the engine in a car to death to get somewhere, let alone haul a wee bit of stuff around. Also, I'd think that always revving the engine up that high won't be very economical, either.
Click to expand...

I did'nt post well known physics regarding bhp just so you could argue against it with a post like yours.

You're posting about how you want an engine to perform?
Ok..

If you want an engine that you don't need to rev much at all, and don't need to change gears at all because you don't want to do that either..
Perhaps you want to pull a mobile home behind it as well..

It's still the effect that makes your car move.


Ridox2JZGTE
My post got deleted after the merge, so here goes :


Torque = acceleration/the rate of momentum delivery to the wheels to get it rolling and increase speed
HP = top speed/the ability to overcome drag due to weight, friction and air resistance once the wheel is rolling
Click to expand...

Wrong.

What moves your car is nothing but the effect (P) of the engine.
 
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I don't need to read your post again because a little thing called Physics and the automotive industry will say you are wrong.
 
sumbrownkid
I don't need to read your post again because a little thing called Physics and the automotive industry will say you are wrong.
Click to expand...

But he's right...

Denilson
Well, I guess you have to read my post again.
You can in theory put 1000000 lbft on a wrench, but still not beeing able to create effect (P).
Effect is what accelerate the car. Nothing else.
Click to expand...

Someone who makes sense! 👍

And with the "torque monsters" thing about the LMP cars, if you have an engine that makes 500hp and 700lbs-ft, then the power curve should be flatter than that of an engine that makes 500hp and 400lb-ft, if it's flatter, then you will be able to accelerate better at a non-optimum RPM then that of the lower lb-ft torque engine.

This is because you might lose 20hp if you go down 2000rpm with the hight torque motor, but you if the power curve is peakyer on the lower torque motor, then it might lose 40hp at 2000rpm less.

You won't have to shift as often with the flatter curve, and it will be easier to drive.


I was also talking about this just last night with a guy who builds drag car engines, so he knows what he's talking about.
 
In terms of solitary figures regarding a car's capabilities, the most useless of all is the peak engine torque. It needs all sorts of conversions and additional information before it becomes useful.

The second most useless is peak engine power - if only because it's torque with a conversion applied to it (of time).
 
Famine
In terms of solitary figures regarding a car's capabilities, the most useless of all is the peak engine torque. It needs all sorts of conversions and additional information before it becomes useful.

The second most useless is peak engine power - if only because it's torque with a conversion applied to it (of time).
Click to expand...

So what exactly is useful then? Torque and power curve/band?
 
Bopop4
But he's right...



Someone who makes sense! 👍

And with the "torque monsters" thing about the LMP cars, if you have an engine that makes 500hp and 700lbs-ft, then the power curve should be flatter than that of an engine that makes 500hp and 400lb-ft, if it's flatter, then you will be able to accelerate better at a non-optimum RPM then that of the lower lb-ft torque engine.

This is because you might lose 20hp if you go down 2000rpm with the hight torque motor, but you if the power curve is peakyer on the lower torque motor, then it might lose 40hp at 2000rpm less.

You won't have to shift as often with the flatter curve, and it will be easier to drive.


I was also talking about this just last night with a guy who builds drag car engines, so he knows what he's talking about.
Click to expand...

👍

Furthermore:
We can use 2 existing cars as an example of what Bopop4 tryed to say..

And let's for the sake of the exapmle say that both cars produce the same amount of Bhp, ok. 👍

Dodge Viper SRT10:
Gearbox: 5 speed (6th beeing an OD)
Bhp: 507 (for the sake of the example)
Engine: 8,2L

BMW M5:
Gearbox: 7 speed
Bhp: 507
Engine: 5,0L

So why does the Dodge come with 5 gears, and the BMW with 7?
Because the Dodge effectcurve (P) is as high in average over a wider rev
spectra due to it's volume compared to the BMW, so it can have "longer" gears = does'nt need as many gears as the BMW to stay on the most effective range on the effectcurve.

Let's say that the Dodge produce 400 bhp in average from 3000-6500 rpm, and the BMW produce 400 bhp in average between 6000-8000 rpm. So the Dodge can work between 3000-6500 rpm (a 3500 rpm range) and the BMW have to stay between 6000-8000 rpm (a 2000 rpm range) to keep up with the Viper.
But since the BMW work in a more narrow rpm range, it needs more gears.

* Anothe fact about the torque is that it's not the same in the engine as on the axle, but the Bhp stay the same.
I.e: An engine produce 200 lbft @ 4000 rpm [(200 * 4000) / 5,252] = 152 BHP
And from the Engine, we have the drivetrain to distribute the effect (P) to the wheels.
Let's say that we have a diff set at 1:3.. All of a sudden, the torque is now 600 (200* 3), but the effect is the same.

* The above example is simplyfied.



Famine
In terms of solitary figures regarding a car's capabilities, the most useless of all is the peak engine torque. It needs all sorts of conversions and additional information before it becomes useful.

The second most useless is peak engine power - if only because it's torque with a conversion applied to it (of time).
Click to expand...

You're good with words, I'll give you that.
But putting it like you did, "The second most useless is peak engine power" implyes that the peak bhp number is irrelevant when it's not.

You're talking about the average bhp over a sertain rpm range. So if the average bhp output over the rpm range is 50 bhp, that's what you get in average acceleration, and therefore the peak bhp is'nt relevant..
But, we're duscussing cars here, and the manufactors don't develop cars with high peak bhp, and then fit a gearbox to that that don't allow the Engine to work in the best range.
Therefore, the peak bhp will give you a decent idea of how fast a car is.

2 similar cars:
Car: A
600 bhp

Car: B
400 bhp

You'll get a pretty good idea of which car will be the faster/stronger one.
Ofc, if car B produce 400 bhp in average over the rpm range allowed by the gearbox, and car A's only allowed to produce 350 bhp in average, car B will be faster..
But their's no such gearboxes/configurations in the automotive industry, so peak bhp will give you an idea of what the car is able to do in terms of performance, in contradiction to the torque numbers.
 
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sumbrownkid
So what exactly is useful then? Torque and power curve/band?
Click to expand...

Everything put together.

You can make assumptions from a handful of bits of information - power, torque, weight, drivetrain - but without the whole dataset (including gearing, power/torque curves and losses, then local atmospheric conditions, CdA, surface grip coefficient, tyre grip coefficient) you can't get a decent picture.

This is why saying "an F1 car has no torque but is really fast, while a truck has loads of torque and is really slow" isn't really an argument against using torque as a metric of performance - you're missing weight and power, and that the F1 car has 1600hp/ton where the truck has 40hp/ton should be a clue - the fact that engine torque is a meaningless figure as a metric of performance should do that by itself.
 

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