What is Torque and Horsepower?

[WindMeUp]

^^True...I was going down to a very fundamental way of looking at it. The crank (rotational) can have torque (force) applied to it that is measurable without moving, that was my point. This was brought to my attention decades ago by somebody far wiser than myself

My wording would have been more accurate if I had stated it as "Torque can be seen as pressure applied to the top of the piston, regardless of weather the piston moves are not." For the application we a talking about, the top of the piston is where it all begins.

[Reswob]

The most basic answer is one from the car world:

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

[backinthesaddleagain]

How about horsepower gets all the headlines, but its torque that shoots ya outta the corners.

[FrugalNinja250]

Originally Posted by WindMeUp

My wording would have been more accurate if I had stated it as "Torque can be seen as pressure applied to the top of the piston, regardless of weather the piston moves are not." For the application we a talking about, the top of the piston is where it all begins.

To my mind, a more accurate way to say it would be that torque is the rotational force on the crank ultimately resulting from pressure applied to the top of the piston, regardless of whether the piston moves or not.

[WindMeUp]

Originally Posted by FrugalNinja250

To my mind, a more accurate way to say it would be that torque is the rotational force on the crank ultimately resulting from pressure applied to the top of the piston, regardless of whether the piston moves or not.

Whatever makes it work for you

[RhinoJC]

The most simplistic of an explanation available while still being accurate as long as you take into consideration that the two forces work together and play off of each other is this:

Torque = acceleration = how fast you can accelerate (best measured from a complete stop)
HP = top speed = how fast you can go

[almost40]

This thread has so many disagreements, it needs politics brought into it.
Its Bush's and Chenneys faulty and that damn Haliburton has something to do with why you cant explain it right.
Obama and the FCC (who now is planning on controling the internet) wont let Wikipedia post the correct, easy to understand info.
Damn I hate this complicated stuff.

[gfloyd2002]

Graduating to video evidence. Torque:

Link to original page on YouTube.

Horsepower:

Link to original page on YouTube.

[Rayme]

I think people get easily mixed with torque and horsepower (in the automotive world) because they both vary with RPM. Some engine has low end torque, and other had high RPM horsepower (which is basicly HIGH END torque)..ad gearing to that and it's enough for somebody looking for a simple explanation to get mixed up.
It's real hard to explain it without getting technical like everybody before me posted hahah!

To keep it simple, horsepower is what make you go fast, faster.

Example: 2 cars in a quarter mile with the same weight and aerodynamic and 5 speed transmission(with standard average gearings):
-Car 1 is a Diesel with 170 HP peak and 350 ft.lb. peak of torque
-Car 2 is a gasoline with 325 HP peak and 172 ft.lb. peak of torque

Which will be at the end of the line first? The car with 325 Horsepower will win EASILY.

I might as well throw that in..why diesel have always high torque number but low horsepower? Diesel oil burns SLOW.
That means the explosion pushes again the piston longer (thus giving greater torque number) and also because it burns slow and by compression (not ignition), at high RPM the explosion cannot be controlled by timing advance like a gasoline engine, and it simply won't rev much higher because the combustion will keep "expanding" while the piston goes up...thus limiting the potential power at high rpm. Caveman description I know haha.

[Ichiro]

Not addressed to anyone in particular but...

[WindMeUp]

Hey it's OK, the horse is not dead...see, it's talking!

[tiggen]

Originally Posted by gfloyd2002

Graduating to video evidence. Torque:

Link to original page on YouTube.

Still one of my all time favorites.

[backinthesaddleagain]

Originally Posted by almost40

This thread has so many disagreements, it needs politics brought into it.
Its Bush's and Chenneys faulty and that damn Haliburton has something to do with why you cant explain it right.
Obama and the FCC (who now is planning on controling the internet) wont let Wikipedia post the correct, easy to understand info.
Damn I hate this complicated stuff.

^^ Funny.

Don't forget to bring in oil types when there are disagreements. I think that torque relates to conventional oil, while hp relates to syn oil. If you change your oil every 3-4K miles your torque will benefit, but if you change it more frequently hp will benefit. Also somehow Chuck Norris benefits from the confusion here. Maybe torque is a defensive lineman while hp might be a defensive back.

Not to mention undersquare vs square vs oversquare configurations (bore * stroke) for a given displacement.

http://www.hotrod.com/techarticles/h...ide/index.html

[FrugalNinja250]

It's hilarious how the discussion seems to imply that horsepower and torque are two separate entities. That's like saying, what's better, amperes or watts?

[gfloyd2002]

Originally Posted by FrugalNinja250

It's hilarious how the discussion seems to imply that horsepower and torque are two separate entities. That's like saying, what's better, amperes or watts?

Amps, baby!

[Ichiro]

Originally Posted by Sungfooo

Can someone please answer this question in the MOST BASIC form. What is Horsepower and Torque?...

Apparently not.

[Flashmonkey]

Originally Posted by FrugalNinja250

It's hilarious how the discussion seems to imply that horsepower and torque are two separate entities. That's like saying, what's better, amperes or watts?

Kelvins are better. I win!

[tiggen]

Originally Posted by FrugalNinja250

It's hilarious how the discussion seems to imply that horsepower and torque are two separate entities.

Ok, I'll bite. You're saying that hp and torque are the same thing?

[Samer]

Originally Posted by tiggen

Ok, I'll bite. You're saying that hp and torque are the same thing?

Not the same thing, but I think the point is they are very closely related.

Hate to repeat myself but:

Power = Torque * RPM

If nothing else, please keep that in mind. I'll even go one further if you'll allow me to explain some of the practical nuance that can get misunderstood.

For the sake of discussion, and for four stroke gasoline engines, a big disadvantage of these engines is they don't generally produce a lot of power until they get to a high RPM. So in the meantime, you're sitting there at the red light waiting for the engine speed to increase while you accelerate very slowly until finally the you get to 8000 RPM and there is finally some power being produced by the engine and the acceleration increases a lot.

A theoretical perfect transmission would completely make this thread pointless. That is, if a bike's (or car's) transmission could be any gear ratio at any time (endlessly continuously varying) then power would be the only number you need to know. Period. Understanding that would be understanding the whole issue. Any quoted engine power, for example 30 HP for the 250 (or whatever the peak power is) only happens at exactly one RPM. At any other RPM the power is less. So if you geared the 250 such that the engine is always at 12000 RPM, or whatever the peak power RPM is and the wheel speed is whatever you want, you'd always be at peak power and by definition peak torque for what that engine could ever hope to produce. Obviously this can't happen so there are compromises for gearing. Even the engine design can be tuned for flatter torque curve with less peak HP or vice versa. Lower number of cylinders (for the same displacement) tend to have more toque at lower RPM than an engine with more cylinders. Again, if you look at the simple equation that precisely means more power at that exact RPM.

Hope this helps someone.

[Eva689]

Wow, I just got my BSc with a theoretical physics major and you guys are making my head hurt.

My father once gave me a fantastic explanation for voltage vs current vs power in terms of water. It's not perfect, but it's close. It can be adapted to torque/horsepower/rpm:

Imagine a hose with water running through it, the rpm is like the speed of the water rushing through, the torque is like the width (or pressure if you like to think of a constant diameter hose) and the horsepower is like the flow rate of water gushing out the end.

Clearly all three are linked and the application determines which one is more important at any given time. As Rayme said about Diesel/Petrol engines, a diesel produces huge amounts of torque, which is why it is great for towing applications or hill climbing - remember horsepower = torque * rpm, so if horsepower is low, this is only useful at low speeds (if we ignore drive ratios for now). On the other hand, a petrol engine produces more horsepower but lower torque, so it struggles to tow anything because that requires torque. However, when speeds get higher, that equation above tells you that if we assume torque grows linearly with speed, horsepower increases quadratically (squared, or much much faster). So the petrol engine is capable of higher speeds. The thing about horsepower is that you can't just apply it, it must be 'required' - so it is easier to think of it as a ceiling, you can't go above it, but it doesn't affect you until you hit it. Torque can be (as a direct result of hitting the throttle) 'applied', so think of it as your jetpack carrying you upwards on the velocity graph (hehe).

Perhaps it would be better to look at a couple examples:

Let's pretend two bikes are both going at the same speed. Bike 1 is in a gear which results in it turning at 6000rpm. Bike 2 is turning 3000rpm. The gearing means that if they wish to accelerate together, bike 1 requires half the torque at the crankshaft, let's say 20 ft*lbs for bike 1 and 40 ft*lbs for bike 2. This means both bikes will produce 120,000 rpm*ft*lbs (or 22.84hp) of power. PLEASE NOTE those power figure are instantaneous, as soon as the bike picks up speed, the power figures will increase, while torque remains constant, assuming smooth acceleration. Assuming both bikes are capable of this, all is dandy.

The problem occurs in vehicles because smaller engines, like ours, have really sharp torque and power curves, so we can't just apply all the torque from manufacturer specs wherever we like. So to achieve maximum instantaneous acceleration, we actually need to be dead on the peak of the torque curve, if horsepower allows (see example calculation above, if power is not available, it simply won't produce the torque we ask of it).

So the short and long of it? Takeoff at your torque peak, horsepower isn't an issue here because you're not even moving yet. Flying out of a corner, sit on your horsepower peak, because you're certainly not accelerating as fast as your bike theoretically can with all its torque, so maximum horsepower it what you require.

Feel free to correct as necessary, I'm on holidays and just wrote this down as I thought of it.

[almost40]

What the hell? No jigawatt when were talking of electrical current??

[Eva689]

Originally Posted by almost40

What the hell? No jigawatt when were talking of electrical current??

Oh I just assumed everybody knew I meant jigawatts when I was talking about current.

[JMcDonald]

Want simple?

Look at a dyno graph:


Follow the HP curve to its peak. If you keep the RPMs around there, you will accelerate the quickest. Breaking it down into torque and RPM and gearing is good intellectual exercise. But, HP has the absolute final say in determining average acceleration given real-world (well, and theoretical) applications, AND is the simplest to grasp conceptually.

Say one is traveling along at 40mph and wants to accelerate as quickly as possible to pass a car. Being in a gear that would put the engine at 12k RPM (on the Area P graph) would give the rider twice the acceleration as one would have in a gear which put the engine at 5500 RPM, because there is half the power at 5500 RPM. This is also despite there being more torque at 5500 RPM than at 12000 RPM.

If one had a CV Transmission that smoothly and continuously varied the gear ratio so that Revs could be kept constant while vehicle speed changed, the vehicle would accelerate fastest if the engine were kept exactly at peak power. For us, doing our best to keep the revs around peak power, when possible, will give the quickest average acceleration.

There are other things one can determine from examining dyno graphs, too. For example, peak torque occurs where the engine's Volumetric Efficiency (VE) is highest, given otherwise constant conditions (like, no variation in intake pressure or timing advance, mostly). Basically, it is at this RPM where the engine inhales and exhales the largest charge mass per revolution. However, peak power occurs where the actual flowrate of mass through the engine is at its highest.

So, looking at the above graph, at 10k RPM is where peak VE is achieved. It is possible (but very difficult and time-consuming) to calculate it on well-datalogged FI engines, but I can't imagine how it would be doable on a carbed engine. In any case, I think it would be safe to say peak VE on this engine is maybe 90%. Assuming other tuning variables stay relatively constant, we can see that if the engine is making 13.24lb-ft of torque at peak power, vs 14.99 at peak torque, that gives us about 79.5% VE at peak power. So yes, the engine is actually most effient at peak torque, but the energy it is capable of putting out is directly proportional to the amount of fuel it burns in a given time, which is where power comes in . Despite having less VE at the higher RPM, it is burning about 7.8% more fuel in a given time, assuming a relatively constant AFR. Thus, there is almost exactly 7.8% more power at 12.2k than there is an 10k. Adding 7.8% to the 10kRPM power of 28.5hp (as eyeballed with a ruler) gives, interestingly enough, 30.72HP.


Unfortunately, discussions about power, guns, and politics almost inevitably the same. People will ultimately decide to believe whatever the hell they want to believe. Some will simply choose to believe all Democrats are gay / all Republicans are racist, a shotgun blast is capable of knocking a human across the room, and the only value of HP is to sell cars.

*shrug*

Happy New Year!

[JMcDonald]

Found some old articles I discovered a while back. I'd recommend reading them in order.

http://www.jacobmcdonald.com/weblinks/hptq1.html

http://www.jacobmcdonald.com/weblinks/hptq2.html

[wyckedflesh]

Torque: is your 60Ft Time
Horsepower: is your ET and Top Speed

Torque is how easy it is to leave the line. Horsepower is what allows you to keep going faster once your rolling.

Adding more Torque won't necessarily add more Horsepower. If I add 10ftlbs of torque at 1500rpm but not have that 10 extra carry through to 8000rpm, it does me no good. I can launch REAL hard, spinning my tire with ease, and then the bike falls flat. Like that real noisy Diesel truck blowing clouds of black smoke to get across the intersection real fast, only to have you blow by him when he hits the rev limiter. An air cooled Buell XB is a great example of GOBS of torque but no RPM to take advantage of it. From off idle to 5000 rpm it pulls like a freight train, but now your moving and as the revs run out, the horsepower falls off too because the torque has already peaked. The motor just can't keep the acceleration going. Now you take an R1, off idle the motor is dead flat. It needs the Revs to get to where the motor makes the torque to get the bike moving. it can't launch as hard as the Buell off the line from idle (I am talking idle to go without slipping the clutch to let the revs rise first) but once the R1 hits 8500, where the Buell is falling off because of the rev limiter, the R1 has turned into a Rocket. Your not in the torque band, you don't need the bike to pick itself up at that point, you just need it to keep going faster!

So if you want more top end horsepower, you need to move where the motor makes peak torque up higher into the Rev range. You can still make say 50ftlbs of torque, but if you originally made it at 4500rpm, when you move that peak to say 6500rpm you just went from 42hp at 4500rpm to 61hp at 6500rpm...

[adamjenkum]

torque= size of ones testicles bigger the testicles more weight it will lift,pull,push etc the torque is probably less than 20ftlbs at 10k but you will have to put it on a dyno to find out

Horsepower= measurement used to compensate for penis size that is always brought up at dive bars (pubs in the UK) if horsepower is mentioned around females it is usually the best way not to get laid. look for the nearest sausage fest and your sure to hear horsepower mentioned at some point, even though the people talking about it have most likely never even seen a dynometer.

rpm--- the rpm the engine is spinning will affect the numbers but if you mention it in public around other males you might get shunned for making them think. try it! when someone says their car has 500 hp ask them at what rpm, their eyes will glaze over and their mind will go blank.

WARNING doing so may also cause their face to turn bright red and their arms to start swinging uncontrollably towards your face so make sure to wear head and eye protection.

You have a 250 ninja it makes around 30hp, more if you invested more money than the bikes cash value in mods. so chances are no one will get angry at your low testosterone/hp numbers

The speedometer also says 130mph even though it only does around 100 with me on it, If I don't eat anything for a day or so and take a fat dump I can get almost 110 downhill with a tailwind. But most people are uneducated when it comes to motorcycles, cars, guns, and just about everything else considered manly, so just do the manly thing lie to them and say it goes 130 saves you the trouble of explaining things.

[Jiggles]

I've never know the difference between torque and hp and generally just ignored torque and looked solely at hp to compare performance in cars and motorcycles. I'm sure many of you on here also don't know the difference or else I would have been corrected when talking about area p dynos. Torque, is really the only thing that matters, hp is largely meaningless, or at least confusing when looking at dyno results. When looking at the area p dyno, you see that hp continues to increase up to 12k, giving the impression that the bike will pull harder and harder up until 12k, but that's not true, max acceleration is actually at the torque peak and then declines after that.

I just thought this was interesting and that many people don't actually know about it. Oh and the way hp is calculated is torque*rpm/5252. This is why on every dyno you see hp and torque are equivalent at 5252 rpms. Hp is just a calculation from torque.

Interesting **** huh?



Interesting reads
http://vettenet.org/torquehp.html
http://www.hotrod.com/techarticles/h...e/viewall.html

[CalvinAmI]

bookworm. er.... internetworm.
GET BACK TO HEALING!

PS: Can you cross your legs or sleep on one side yet? That's what killed me when my knee was all busted last year. Like 3 weeks before I could sleep on my side. SNORE CITY!

[Jiggles]

Might as well learn well I'm down and out. And actually I just take a Percocet then turn over and sleep on my stomach, but that's beside the point! Back on topic!

[Liist]

If torque was the only thing you needed for performance, then we should all get diesel cars.

[Alex]

/merged

[Jiggles]

Originally Posted by Liist

If torque was the only thing you needed for performance, then we should all get diesel cars.

It is all that matters, where the torque peaks also matters and stretching it out over a long rpm also matters. I think that looking at a torque curve matters a hell of a lot more than an hp curve, afterall hp is just torque*rpm, I don't think it paints as accurate a picture as torque does

[Jiggles]

Maybe I'm still confused about the topic haha, ok let's say we have 2 vehicles of identical weight, each is producing a different amount of torque at a different rpm but they are producing the same amount of horsepower, will they have equivalent acceleration or will the vehicle producing more torque accelerate faster?

I haven't had a physics class in a while but even do we never got into hp vs torque -_-

[Alex]

Read the thread from the beginning.

Your question can't be answered absolutely without knowing the torque curve (or hp curve) of the two motors. The vehicle that makes the most cumulative hp (area under the curve) over the entire time period of acceleration will accelerate fastest. That can be because of a wide and flat torque curve where they are making good power across the rev range. Or it could be with a narrow power band, but optimal gearing so the vehicle stays making good hp throughout.

[Jiggles]

Brains hurts, ima just go back to living in an all hp world where I was happy

[Jiggles]

Originally Posted by Alex

Read the thread from the beginning.

Your question can't be answered absolutely without knowing the torque curve (or hp curve) of the two motors. The vehicle that makes the most cumulative hp (area under the curve) over the entire time period of acceleration will accelerate fastest. That can be because of a wide and flat torque curve where they are making good power across the rev range. Or it could be with a narrow power band, but optimal gearing so the vehicle stays making good hp throughout.

Well let's just say instantaneous acceleration at that one particular point where they have the same hp but different torques, for those few milliseconds, will acceleration be the same?

For example, at 50 hp on a zx6r and zx10r, for the next few milliseconds, will they accelerate at the same rate, ignore all gear ratios and that crap, we're being theoretical here!

[Alex]

If they are both making exactly 50 hp, and for the purposes of this argument they continue to make exactly 50 hp for the next few milliseconds, they will accelerate at exactly the same rate. (given identical weight, gearing ratios, etc.)

[Jiggles]

Ok, so my original theory was off but now I understand the relationship between rpms torque and hp, not sure if I could explain it to anyone but I get it and that's all that matters

Learning is fun!

[crispy23]

Wow, looks like a bunch of stuff that will make my head hurt in here.

Here is how it was told to me a long time ago and maybe will help someone looking for a "basic" example.
If you are trying to turn a wrench or ratchet, the force you are applying is torque. Once the bolt moves, your force is doing work and that is when horsepower is to be measured.

Maybe that is right and will click for someone.

[Jiggles]

Such a simple explanation really doesn't help you understand how it applies to cars or motorcycles though