What does Torque in a Car do?

You've seen it a bunch of times when you're reading the specs on a new car: the number of foot-pounds of torque that it puts out. Well, the 2009 New York Auto Show just happened, and I was reading the synopsis of a new Mercedes that just came out:

369 foot-pounds of torque, it says. (That's 500 Newton-meters, for you mks/SI folks.) Torque is the amount of "turning power" you have, much in the same way you turn a wrench. 369 foot-pounds means that if you had a wrench that was 1 foot long, and applied a force of 369 pounds directly perpendicular to that wrench, you would get 369 foot-pounds of torque.

Well, what can this do to a car? The answer is: cause it to accelerate! The torque specification they give is the maximum torque of the internal-combustion engine, which is usually a higher value than the actual torque on the wheels. (See wikipedia for more details.)

But this torque can tell you a lot about how fast the car can accelerate. Let's turn it into a physics problem. We'll assume that this "500 Newton-meters" is an actual, legit value for how much torque the tires experience. We can estimate that the mass of a typical car is about 1500 kg, and that the typical distance between the center of mass of the car and the wheel's rotational axis is about 20 cm; this gives us a moment of inertia for the car of 60 kg m^2. The car's wheel size plus the sidewall radius of the tire is about 20", or 51 cm.

The acceleration of this car? 4.25 m/s^2, or (more commonly), it can do 0-60 miles-per-hour in about 6.3 seconds. Want a car that can accelerate faster? Here are the things that can help:

  • more torque (duh),
  • a lighter car,
  • a lower center-of-mass (closer to the wheel axle in height),
  • larger diameter wheels & tires,
  • and an engine that can output this large amount of torque over a wide range of engine speeds.

Want to know which street-legal car hold the world's record? This Sunbeam Tiger does 0-60 mph in 2.6 seconds!

So yes, it's just a prototype, and in theory it can do it in 2.3 seconds, but that's pretty good for some real-world physics, and now hopefully when someone brags to you about how much torque their car has, you'll actually know what they're talking about!

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By francis mwangi (not verified) on 18 May 2012 #permalink

A post on how engine torque relates to the acceleration of a car is really missing something if you fail the mention the gear ratio.

Even if we ignore internal friction and such, the engine torque is related to the torque on the wheel by the gear ratio: if the total (transmission times differential) gear ratio is 10:1, for example, so that 10 revolutions of the engine results in one revolution of the wheels, then the torque exerted by the wheels is "geared up" by a factor of 10 over the torque exerted by the engine. For the Corvette referred to in the linked wiki article, this ratio ranges from 10:1 in 1st gear down to about 2:1 in 6th gear.

In low gear, even with losses, the torque available at the wheel should be quite a bit higher than the torque at the output of the engine. Nothing comes for free, of course: the lower the gear (and therefore the higher the ratio as I've expressed it), the faster the engine must spin to make the car move the same speed, so the more power the engine must generate. If we had a perfectly lossless, infinitely variable transmission and drivetrain, it wouldn't matter one bit how much torque the engine had at the output -- the only thing that would matter would be power, which is the product of torque and angular velocity.

I've hear car and motorcycle enthusiasts use "engine torque" as a shorthand for how much acceleration is on tap without downshifting to change the gear ratio...

Only the axle he1ght is relevant to the resulting acceleration. The c of g height has only small secondary effects at normal car power levels. Powerful vehicles would experience pitching moments in response to differences between axle height and c of g height. In extreme cases, like rear wheel drive drag cars, maximum acceleration would be limited by the vehicle becoming unstable in pitch and flipping over backwards. (Unstable as any pitch-up puts the c of g even further above the thrust line, and eventually horizontally closer to the axle.

Car manufacturers: all torque and no action! It's a pity they talk torque and turn green when you ask them how green their vehicle is....

If I understand it at least partly correctly, 'torque' is engine power at low rpms, while 'horsepower' is the same measurement, but taken at at a specific higher rpm.

Some engines don't develop their maximum power until higher rpms are achieved, while others, like diesels, achieve most of the power quickly at the lower rpms, and actually suffer power losses as rpms get higher.

To accelerate quickly from a standstill, then, requires power at low rpms, thus, torque foot pounds is a much more reliable indicator of car acceleration performance than horsepower foot pounds would be.

The whole discussion gets mixed up in most people's minds because somehow over the years the concept of 'torque' and that of some kind of 'twist' have become entangled.

By Gingerbaker (not verified) on 24 Apr 2009 #permalink

Torque in an engine and horsepower are related, but are not the same. Horsepower is the total power output of an engine, while torque measures the "turning/torquing ability" of the engine.

Practically, torque is a better measurement of how quickly your car will accelerate, while horsepower (relative to weight) is a better measure of your car's top speed. I have two vehicles, a 1997 toyota with a top speed of ~110 mph, and a 16,000 pound school bus with an 8 L diesel engine, with a top speed of ~60 mph, going downhill on the highway.

That Awsome Sunbeam Tiger has awsome accelaration twice as the new 2010 chevy challenger.

I believe the car "Red Victor" actually holds the record for the street legal car, doing 0-60 in about 1 second.
Correct me if I'm wrong, please.

^^^^ Red victor , yes. its knot to 60 in 1 second flat. theres a video as well on youtube. check it out.

really nicely explained torque vs hp. I like the wrench example. Thx

Sorry but the fastest street legal car in the world is actually a 1970's Vauxhall Victor thats running over 2000bhp. Has MOT and everything, Just look for it on Youtube, but it does 0-60 in about 1 second lol.

Some engines don't develop their maximum power until higher rpms are achieved, while others, like diesels, achieve most of the power quickly at the lower rpms, and actually suffer power losses as rpms get higher.I would like to know if the engine of 190Nm @2000rpm is better than the engine 140Nm @3000rpm?

By rakshpal singh… (not verified) on 09 Sep 2010 #permalink

Dear sir,
i would like to know the cc,torque,displacement & bhp terms used in car.If you give me details with examples,i shall be thankful to you.
Eagarly waiting your reply

With regards
Sunil Kumar(improvement team)

Hmm,,interesting article about the torque.I guess greater the torque ,lesser the force you need to use to complete the task.That is a bottom line i guess.

Hi, so if there are more torque available at the low end, does the engine consume more fuel?

Hi, so if there are more torque available at the low end, does the engine consume more fuel?

Torque isn't a better indicator of a car's acceleration power. Diesel engines have massive amounts of torque but this doesn't guarantee exceptional acceleration. E.g.

Audi A3 2.0 TDI's make 320nm@1750rpm where Corsa GSi 1.6's make only 150nm@3200rpm. Despite the 400kg difference in weight, according to this torque theory the A3 should have far more acceleration from standstill. But this simply isn't the case, as even with its turbo boost the A3 only overtakes at 60mph, with the corsa quite far ahead during 1st and 2nd.

"Horsepower is another measure of engine power, but it is based on torque. Horsepower is the abiltiy to do work over a period of time. Other things are taken into account, but it is based on torque so the two will follow each other to some degree. Torque comes on first because it is the instant twisting force. Horsepower is built as you get going and things like momentum of engine components come into play. "

Hi there i have a query about torque and kilowatts.
if i car for example has 3oo torque yet 200 kilowatts and another car has 175 kilowatts and 500 torque what would be faster or more quicker acceleration wise.

cause one car has more kilowatts but alot less torque yet the other one has less kilowatts but more torque?

Max speed depends on power, acceleration at low speed set by torque. Acceleration at high speed needs torque to kick the car faster but you need excess energy to allow work to be done.

But, since maximum legal speed is ~70mph and you can maintain that on the flat with less than 50bhp with modern efficient bodyshapes, you don't really need much power to drive legally.

Sorry people, you are mixing units left and right, confusing power with force or torque. For acceleration it is the torque AT THE WHEELS per unit mass of the vehicle that counts. The amount of torque at the engine output shaft does not matter a diddly squat as the torque can be increased by gears. The engine power is proportional to the product of the torque and RPM. So the initial acceleration is limited by the grip of the wheels, the acceleration at higher speed is limited by the engine power (per unit weight) as at higher wheel RPM the more powerful (HP)engine can deliver higher torque. From the car operation point of view a flat torque / RPM engine characteristic as it is more important: it is more forgiving of gear shifting.

how doea i find torque of a car by a simple technic

By nitin kumar (not verified) on 03 Mar 2012 #permalink

To calculate motor full-load torque, apply this formula:
T = PH x 5252/rpm where T = torque (in lb-ft)HP = horsepower
5252 = constant;rpm = revolutions per minute.
There was wrong way to get focus to motor development, its torque and interior acceleration system by gas or magnet field from 0 to 60 when energy was inexpensive in USA at long time ago.
However the way of saving energy and right car power calculation is focus to friction between wheels and land that moves the land vehicle according to Third Newtonâs law. The simple formula T= vehicle weight with load x coefficient of friction x radius of wheel= 3,000 x 0.7 x 0.04=82 lb-ft is sufficient motor torque that moves car from stop that requires highest torque than in movement process.
This torque magnitude is not requiring large motor power because first Russian car without gear-transmission has motor of two horsepower and 18 mph forward speed at 1896 and motor of 30 hp produces 70 mph with sufficient torque at 1911. Other words, acceleration system by gas or magnet field uses too large motor power because torque magnitude is reduced by increased revolution of its shaft according to upper formula where motor power has constant magnitude of physical volume.
Today USA patent 8,011,274 at 09/06/2011 discloses revolutionary way to save energy by using shift gearbox apparatus designs to move car without acceleration by needed speed as will and they use only idle speed or maximum torque of motors that open opportunity to reduce its cost, emissions, and noise.

sir i want to know that why the torque is provided in front wheels in new cars? what is are benifits?

Guys,help me out in simple themes,mayb torque can accelaretes cars more quickly in startpoint 4 e.g some sport artlecte do have accelecration,but loss power in long run.correct me,if am wrong.

Please can you guide me about the torque which effected when engine was running high R.P.M

wants to remap audi a4 B6 model 1.9tdi,130bhp with 150000k on the clock.She is in very good condition but needs to be waken up.Can she take the extra power if i
if i get her remap.Please help.

Guys, The article was about giving people new to trucks/cars a SIMPLE understanding. While it was fun reading your hilarious conversation that was ridiculously disjointed and failed to explain the complexities of it all, you probably just confused a would-be car enthusiast for life.

sir,
why the condition of maximum BHP and maximum torque
does not coincides?
what does the BHP contribute for acceleration and weight lifting?
?

By sudheeshkumar (not verified) on 02 May 2013 #permalink

Thanks to "Gingerbaker" for an excellent link.

Never thought I'd say this but "Thanks Zanfief For teaching me science!"

Dear sir,
i would like to know the cc,torque,displacement & bhp terms used in car.If you give me details with examples,i shall be thankful to you.
Eagarly waiting your reply

By Satwant Singh (not verified) on 27 Aug 2013 #permalink

2 things wrong in this article, "The torque specification they give is the maximum torque of the internal-combustion engine, which is usually a higher value than the actual torque on the wheels" FALSE, through gearing torque at the wheels will be considerably higher, with 1st gear averaging 3:1 and the differential averaging 3.5:1 an engine producing 100 lbft of torque will apply 1050 lbft of torque to the wheels (neglecting friction losses) the second wrong point int he article is that bigger tires will result in faster acceleration, FALSE it does exactly the opposite, the bigger the tire results in less force being applied to the ground resulting in less acceleration. Larger tires give you a higher top speed but will take you considerably longer to get there.

Rick, I severely doubt you are correct here.

Unless the wheels are 1/3 the size of the connecting rod for the pistons to the crank, 3:1 gearing won't do that.

Guys help me out, I'm having a hard time understanding torque. My husbands trucks drive shaft twisted and broke off entirely, and it was said too much torque was applied. The fact is the truck was brand new, and been just put on the road for work. Now, my husband has over 30 years of truck driving experience, and certainly knows how to handle this truck properly. When the truck (2012 International 4300) become disabled, the truck was about 3/4 full loaded with wood chips, and broke down within city limits of 25 mph. We thought this would be covered under warranty, but it was denied for the reason of external damages. A few weeks prior the trucks drive shaft broke, all tires were stolen off the truck and the truck was left on wood pieces. This happened at a place where we had work done at the truck, where the truck was left overnight. Could the drive shaft have been damaged by being raised lets say with a lift gate at that time and then just broke down a little while later ?

I'm planning to buy a pick-up truck and please give me an idea which is better, one having a maximum torque of 294 N-m @ 1400-3400 or one with 343 N-m @1400- 3200 rpm?

By Dan dantes (not verified) on 11 Feb 2014 #permalink

Please advise me which 3.0 L pick-up truck is better based on manufacturer's torque specs. One with 294 N-m @ 1400-3400 rpm or the one with 343 N-m @ 14000-3200 rpm?

By edison alerta (not verified) on 11 Feb 2014 #permalink

This might be a stupid wuestion but i dont understand how a lower COM will help, doesnt a closer COM mean lesser radius thus implying lesser moment of inertia?

In a car, when the torque of motor/engine is max what should the driver do? upshift or downshift? the objective is to reduce fuel consumption and increase efficiency of the car power.

By Roemer Timbre (not verified) on 25 Jul 2014 #permalink

All that you people are saying is bullshit. If you want to know the scientific and true meanings of these terms read this my post. If you want to know the overal output of an engine look at POWER. Torque is NOT the figure you should be looking at although most people do look at it. If you look at torque you should also look at RPM because both contribute equally to the POWER output which is the only useful figure here.

POWER = Torque x RPM
A car may have low Torque but with lots of RPM and ultimately lots of the useful POWER. This is typical of most petrol engines which generally have more power than comparable (same displacements) Diesel engines. Another engine may have lots of Torque but lower RPM and this is typical of Diesel engines. In other words RPM should tickle the same excitement as Torque and they should be looked at TOGETHER, or just look at the overal product, POWER which is the ONLY function that translates to acceleration and top speed. This is not an oversimplification. You can look at specific cars with the same model and various engines, then compare the overal acceleration and top speed.

Compare Mercedes e350 (gasoline) to e350 cdi (diesel). They have same displacement but the petrol has more POWER, better acceleration and higher top speed despite the fact that the diesel has more torque. The higher torque of the cdi is more than overcome by the higher RPM of the petrol version giving the petrol version more power overal. The only 2 important parameters to look at when choosing a car are POWER (hp or KW) and fuel consumption. When you look at TORQUE you should look at RPM as well because one will compensate for lack of the other.

I would like to know the torque and power of the HZJ80R
Toyota Landcruiser
Cheers Stan

Let me know of torque required to crank engine to start it.
In oz. inch. / foot lbs. / kgs cms. units
Engine description 4 cylinder 1.4 lit. capacity diesel engine.
Thank you,

By Sahasranaman (not verified) on 14 Jan 2015 #permalink

0-60 in 1 second? I'm not sure I buy that. It would be pulling over 2.7 Gs. Without downforce, wouldn't that require an impossible amount of friction between the tires and the road?

No, it doesn't require an impossible amount of friction, because there is no limit to friction on non-smooth surfaces - the tyres are soft and sticky and literally mould themselves to the track.

Top fuel dragsters do 0-100 in around 0.8 seconds, and touch a momentary 10g at launch, followed by 5g for the rest of the quarter mile. Quite a ride. They aren't road legal, of course!

good information thank you

Larger diameter wheels and tires will decrease acceleration and increase top speed, they will not improve acceleration as noted in your article.

This seems to go on forever ?

You need the same model 2.6Lt cars, both turbo, with , say 500awhp for response and 600HP built for top speed

One has been modified for response and the other HP, this is simple as I am just going off my experience

One would have a different set up for response , smaller turbo, cams ect , as to top speed with larger Turbo and cams.
Line them up on the street and run from idle the responsive set up would smash the top speed set up and belt it around the twisty stuff, I think :/
Launching at high revs may be a bit different, just looking for answers :)

You wouldn't use a turbo for responsiveness, you'd use a bigger engine or a supercharger.

Dudes, please stop repeating what you heard on a petrolhead website and understand it first.

Power.

On the flat, you expend no power at speed. No acceleration = no power dissipated.

What dissipates power is road friction, engine friction, air friction. Lower RPM = lower engine friction.

Sticky tires=more friction. Wide tires=more friction.

Air friction depends on aerodynamics of the shape, not the engine, and velocity squared.

So far, the diesel engine experiences less need for power at high speed. All other factors than RPM can be identical between the two types of car.

If you have insufficient torque, you will be unable to accelerate beyond that point at which your friction-induced torque equals the generated torque by the engine.

Diesels have the advantage here, too.

If you want to know more about it, ask a professional pilot about negative p-sub-s. You can find yourself in a region where you have plenty of spare energy but are unable to generate any acceleration and will drop in speed. No matter how hard the engine works.

Now the limit of acceleration is how you develop the engine torque into acceleration on the ground. And bigger wheels can let a high torque translate into higher acceleration.

Look at the drag racers.

They will also be stickier, which means a better rate of acceleration, but being sticky, they generate much more friction, and your top speed and fuel economy is tanked.

So to acceleration, it's whatever is left over from the engine to the ground, top speed is where your dissipated power equals the various power losses in moving at that speed.

And the heavier the vehicle, the more torque required to accelerate at the same speed. Which is why you get diesel, not petrol, trains. Diesel engine trucks.

Not for fuel economy, but because they're so heavy the limit is the torque generated by the engine.

Meanwhile for much lighter vehicles, the limit is how much you can pull off without wheelspin. Engine torque is much less of a problem in achieving maximum acceleration.

Your claims for petrol are mostly BS caused by a simplistic ideal of what a car does to go. They are true for a reason other than the one you claim.

Finally, because petrol is induced combustion, it can be overdriven much easier than diesel spontaneous combustion, therefore RPM is easier to attain, as long as you don't give a monkeys about the engine lifetime or fuel economy. And for formula-X racing cars, they are designed to extract downforce to ensure that the driving wheels can maintain traction, meaning diesel would be able to perform better if you plonked a street car road legal engine in it. But they can run 10,000RPM in a petrol engine, but are limited to half that for diesel designs. That may be able to be improved by ignition chamber designs, but it's easier to be right at upping the RPM to get more top speed out.

And with MASSIVELY sticky tires (you need a full lap at high speed to warm them up or they don't work for shit, ask Richard Hammond), again, top speed limits will appear because of power output limits, not torque.

A small twisty track like Monaco would show a diesel engine off very well. But it would do really REALLY badly on the long straight of most of the others.

Instead of repeating what you've heard, try looking at the situation as to what is physically going on.

You won't repeat tired old myths anywhere near as much then.

Diesels also have a problem for racing in that they have a narrow power band, therefore you need a lot of gear changes, though you get less finickity power out on your gear change timing. Petrol you need to near-redline it to get the maximum acceleration, and redline before changing up at a speed too high to keep up. Diesel you can get away with changing when your able, since power and acceleration are more evenly distributed in the available (narrower) power band.

To Ian. Who gives a fuuck how "green" a vehicle is?? You will be the idiot wanting to step up and pay even more taxes for something that is not even happening. I am a scientist and science that is done by computer models (atmospheric) is never settled until it works. Why can't they predict the weather in a week? Because it is very complex. If they still cannot do that than how do we take seriously 50-100 projections? Green cars are idiotic and that's why I have 2 911's and not a fleet of Prius'!!

"You will be the idiot wanting to step up and pay even more taxes for something that is not even happening"

What is not happening? Got proof and a theory of how it isn't happening? Or are you just sticking your head up your ass and going "Nope! Can't see a thing!"?

"I am a scientist"

No you aren't.

"and science that is done by computer models (atmospheric) is never settled until it works."

Proof you aren't.#

"Why can’t they predict the weather in a week?"

They can. ECMWF tells you how liable to prediction the weather is. Sometimes it is two weeks or so, most of the time it's near or around a week, sometimes it's only two days.

"If they still cannot do that than how do we take seriously 50-100 projections"

By looking at what the difference between climate and weather is, dumbass.

"Green cars are idiotic and that’s why I have 2 911’s and not a fleet of Prius’!!"

You are an idiot is why you have no 911's (unless you mean calls to the emergency services for the alien abduction you reported...).

BTW, the Prius will have better torque than the 911s.

At least you now concede your ignorance.

Any advance on "you ugly", you cretin?

So, SL et al, you see the actual problem here.

Ethan get this fuckwit out, please.

I am a scientist and science that is done by computer models (atmospheric) is never settled until it works.

If you are a scientist you are apparently one of the rare breed who is completely clueless of statistics in general and time series analysis in particular.

I have a 2014 F-150 with the Ecco Boost. This summer I pulled a 32' travel trailer and could not understand why my engine was always in the 2000 rpm range even on straight flat highways and of course sucking back gas.Some friends have suggested I add a torque unit to my truck. Can someone please explain how that would work to me

Thanks alot

By Dave Elder (not verified) on 16 Sep 2016 #permalink

Actually Engine power and Torque both are related.
Works are different.

Nothing is better than a classic SAAB 900.

How about making love to a beautiful woman?

(change gender according to preference)

How about making love to a SAAB 900!

Torque is not the same as power, obviously:

Torque is τ=Fd
Power is P=W/t

They have different units, so they cannot be equal.

W=Fd
P=Fd/t
F=Pt/d

and F=τ/d

so τ/d=Pt/d

τ=Pt

Torque equals the product of power and time.

"How about making love to a SAAB 900!"

It's exhausting.

Uh, I hear.

PS on your Torque thing, there's a weird thing about mechanisms, most readily found in a hard core flight sim manual.

There's a term "p-sub-s", and you can have powerful enough engines to get you faster, but if the region of the power enevelope you are flying in is one with negative p-s, you will be unable to accelerate and will lose speed no matter what. But if you convert some potential energy to speed, you can get fast enough that even back flying the same envelope as before, you can still go faster.

Torque and energy are more complicated than the simple school-level mechanics you are seeing.

They are as complicated as you want to make them. I just had had to point out that they are not equal, and what their formal relationship is.

Perhaps you can find the Gibbs Free Energy of gasoline combustion for us, so we can calculate the theoretical power of the Mercedes engine above. Then we can find out its' efficiency based on the wheel horsepower!

It sounds like you are dying to show off some wicked math.

HI guys, power and torque are complement to each other, in simple statement torque cause to accelerate the car when she is standstill, after accelerating the car it is the power cause to pick up speed( work/time). More torque makes towing ability better.

By Captain Azizi (not verified) on 18 Oct 2016 #permalink

How does one calculate " 4.25 m/s^2" for acceleration, using the above data? I understand how to get the moment of inertia, 60 kg m^2. How do you apply the sidewall radius of the tire is about 20″, or 51 cm, and the other information supplied?

By Highpointer (not verified) on 17 Nov 2016 #permalink

How are horsepower and torque related? if you say torque results in acceleration what does horsepower help in and what does center of gravity do as well?