CraZydudE

Can anyone tell me what is a torque, and what it does?

TSeniorX

As strictly a "lay person" when it comes to cars I can't tell you anything other than - it's good to have. But believe me, there are some real experts on this board who will be able to cite chapter and verse and provide so much technical detail you may wish you never asked the question!

e_lectro

What is torque? Answer

jihan3

Torque is a measure of rotational force.. a foot-pound of torque is a pound's worth of force a foot away from the axis of rotation (in a direction perpendicular to the axis of rotation). Doing a search on google will probably give you a much better explanation, complete with pictures.

CraZydudE

thx for the replies everyone. 1 more question, is it better to have higher torque lbs ft or lower torque lbs ft?

fdl

torque = turning force. So yes the more the better!

TSeniorX

All kidding in my first post aside CraZydudE, isn't it nice to just throw out a question that's important to you and have the experts come to your aid? So, how does all of this register on your Newton-metre?

Brad

That sounds just like the tummy turmoil I had exactly one week ago. In that case, more torque isn't better. 'Round and 'round and 'round. Yup, that's what I had!

Brad's Tip for the Day: A beer is actually good for torquey tummy turmoil!

Does torque have something to do with pulling power? Is there a trade-off between torque and accelleration?

larchmont

Hey, I don't think he was asking about physics!

Try this link:

http://www.autospeed.co.nz/cms/article.html?&A=0744

(Not that I understand it, but there it is.)

TWong1200

I say it simply, "the twisting strength."

kenbiddulph

In terms that we can all understand and appreciate, its the amount of brute force that spins the wheels. Its that kick in the pants feeling you get from driving a V8.

TSXautoXer

Please correct me if I am wrong:

More torque = easier to fight inertia = faster acceleration?

More HP = more pulling power = higher top speed?

finalheaven

I believed in this long time ago. Until one of my friends told me it wasn't exactly like that. He explained but i completely forgot what he said.

larchmont

Funny, we all have kind of a concept of it but aren't sure we really know.

My sense of torque is what I think TSXautoXer meant by "faster acceleration." I think of it as: how quickly and powerfully the acceleration begins kicking in when you plug for it.

I think of horsepower differently from what he said -- not just top speed, but the amount of power that exists. Torque, I think of as how readily you get the power delivered.

A lot of our members I'm sure know these things EXACTLY. But they're not kicking in because their weekend torque is low.

LiamG

It might be easier to understand if you think about applying torque yourself. That's what you do when you apply a wrench to a nut. If you can't get the nut loose, you need more torque. You can get that in one of two ways: (1) get a stronger friend to apply more force to the end of the same wrench or (2) get a wrench with a longer handle. In ether case it's the force applied times the lenght of the handle that counts; that's the torque applied. Now the power that you generate is the torque you apply times the rpms that you turn the wrench (and nut) around at. (There is also a constant you multipy by that depends on the units for rotational speed, force, and length you use as well as the units for power you want. Typical units of power include horse power, watts, and BTU/hr. The units that are commonly used depend on the application you are talking about as well as the country you are in.)

larchmont

Great stuff.

But I still say, TOO MUCH PHYSICS AND NOT ENOUGH "CAR." How about telling us exactly what it means about cars, which is what I think he meant in the first place?

LeeLee

Torque and Power are very different concepts. Given that, comparing the two directly and saying which one is better for what kind of vehicle performance is rather silly.

Torque is a measurement of force. It's a "how much" type of measurement. i.e. How much can you dead lift? How many hot dogs can you fit in your mouth at one time?

Power is a measurement of the rate at which work is done. It's a "how fast" type of measurement. i.e. How much weight can you lift in one hour? How many hot dogs can you eat in five minutes?

During accelerating, a car builds energy in the form of speed. How quickly a car can gain speed is a "how fast" type of measurement. So "how fast" a engine can deliver energy directly translates into "how fast" the car can accelerate. "How much" torque is rather pointless in this regard.

Now, more of both is always better, but when you want to compare engine performance, crank power is always a far more meaningful measurement. Don't believe me? Compare the 155lb-ft 90HP VW TDI engine's performance to the 111lb-ft 160HP Honda B16A2. A VW Golf so equipped takes 12+ seconds to reach 60mph, 5 more seconds than the previous generation Civic Si.

Another benefit of looking at crank power is that power is not affected by gearing. You can effectively compare two car's power to weight ratios without much consideration given to the two car's gearing. However, comparing crank torque is a completely meaningless exercise since torque is multiplied by the gearing. So while one engine may have less crank torque than another, the transmission it is attached to may result in more *WHEEL TORQUE*. This is evidence of the fact that given any two engines, matched with optimal gearing ratios for a given vehicle speed, the higher powered engine will always deliver higher wheel torque, and thus superior acceleration!!! So every time some VW geek comes to you and brag about his 155lb-ft of TDI crank torque, tell him you laugh at his false idol and show him the far superior wheel torque of your Civic Si.

Now lets throw in some "but"s.

Engine torque and power is not a single number, but rather a curve that starts from idle upto fuel cut-off or mechanical limits of the engine, which ever decides to kick-in first. The ability of an engine to accelerate a car depends not on its peak HP, but rather the area under the HP curve. The bigger area this is, the faster the car will accelerate.

Honda engines by their small displacement and high reving nature have a more steeply sloped HP curve. This means given the same peak HP, a Honda engine will have less area under its HP curve than say a BMW engine at lower RPMs. This means at lower RPMs, such as the RPM at a dead launch, a Honda will not accelerate as quickly as a BMW of the same peak HP rating. This explains the inferior light-to-light performance of high reving Hondas.

However, at high RPMs, Honda engines breathe far better and maintain their power output up to redline, resulting in more area under the HP curve at these higher RPMs. This is why when you flog the sh*t out of a Honda engine at high RPMs, it delivers performance found in no other engine.

As you can see, a vehicle's performance can be completely predicted given its engine's HP curve. However, HP curves are not readily available and who the heck has time to integrate two HP curves to compare their areas? What is readily available are peak HP, peak torque numbers, and the RPM at which they occur. Therefore some general rules of thumbs can be used to predict the likely performance of an engine.

Given two engines with the same peak HP rating, the one with the higher torque number likely means that its HP curve is not as steep, thus it will perform better at low RPMs. This is the source of people's love for large engines with their high torque numbers: they love a car that launches hard from slow speeds. All else being equal, a higher torque number means the car is more "drivable" at low speeds.

What does this all mean? It depends on what you are looking for and the type of driving you do. If you want an easy-cruiser that gives you that satisfying push in the stomach every time you leave a green light, then find an engine with high torque numbers. On the other hand, if you enjoy most of your driving at speed, and enjoys the exhileration of taking an engine up to its performance peak at least a few times a day, then find an engine with high HP numbers.

Me? I want both, but if I had to choose, I'd pick the higher HP, because all the torque in the world can't keep a car from being a dog at anything above 15mph.

finalheaven

Now that is a good explanation for real world cars. Having both if of course better i assume. But yes hp over torque.

lshenretty

All that gives us is the teaser. I guess next week they'll talk about what I want to know - what happens when you raise one and hold the other constant? - what impact does that have on how a car accelerates at various speeds?

But thanks for the link.

Edit: Nevermind. Just read LeeLee's white paper on the subject.

LeeLee, don't ever go back. We need you here. Good stuff. Thanks.

LeeLee

Power is a function of torque and RPM. You can't change an engine's HP curve without changing its torque curve as well.

Toque and Power are not independent quantities that you can isolate and adjust to your taste. From the torque curve you can derive the power curve. And the power curve *ALONE* tells you exactly what type of behavior your car will have at all RPMs.

Small displacement high reving engine with a flat torque curve such as the one in the S2000 will have a steep HP curve, which will give you adequate low-RPM performance, strong mid-range performance, and exhilerating top end performance. Such a car is best driven on the boil, using a slick 6-speed manual to keep the engine in the high RPMs and maximizing the area under the HP curve.



A medium displacement engine with a bell-shaped torque curve will give you a less steep HP curve. Power is still best at high RPMs but now there is more power available at low to medium RPMs. This engine is "easier to drive" at low RPMs, and *may* benefit from a 6-speed. At higher RPMs, this engine noticeably runs out of breath and is not as exciting to drive. Such a car would be easier to live with as a daily driver yet still provide a high level of performance when pushed. The TSX's K24, and TL's J32 are fine examples.

A high displacement engine with a early torque peak that tapers off dramatically at high RPMs such as the VW's TDI, some turbo-charged engines, and most truck engines will give you an almost-flat HP curve. With the power curve being so flat, such a car needs multiple gears only for top speed purposes - 4 speeds is enough, 5 is okay, and 6 is a definite waste. The car launches hard from a dead stop but dies quickly as RPM builds. If you want to pass, down shifting doesn't do much other than add engine noise. These types of cars are most suitable for towing heavy loads.



These are the three general types of engines and their suitability-to-task. Most cars fall into these three categories.

LiamG

Well, matter how you cut it, power is always a constant times torque times rpm. The car's acceration in given gear is always proportional to torque. Double the torque and you'll double the acceleration. (Well, not quite true because of fricition and drag, but close.) Horsepower comes in because the torque you can put to the wheels is always proportional to the horsepower generated at that rpm divided by the rpm. A car that generates 200 HP at 5000 rpm will be able to accelerate twice as fast at 5000 rpm as a car that generates 100HP at 5000 rpm. (Assuming same car drag and the HP is measured at the wheels.)

larchmont

I'm still waiting.

I still think nobody has answered the original question -- not like how the original post meant it, and not like how I wonder about it either.

I imagine it's buried somewhere in LeeLee's stuff, but please -- could LeeLee, or anybody, try to state it in one single clear sentence? WHAT IS "TORQUE" AS IT RELATES TO A CAR, IN ONE SINGLE CLEAR SENTENCE?

I took a stab at it, but I don't have any confidence that I was right:

My sense of torque is what I think TSXautoXer meant by "faster acceleration." I think of it as: how quickly and powerfully the acceleration begins kicking in when you plug for it.

Is that about right?
If not, could someone try to give the correct, simple, one-sentence explanation? Thank you very much.

finalheaven

Bah all we need to know is the more hp and the more torque = better.

larchmont

No, I must know -- WTF IS TORQUE??????

No more physics, please -- and I was even real good at it, but that was a long time ago --
Just plain English, a simple declarative sentence that even a senile person can understand.....

fdl

I didnt think my answer could have been more simple.


Just like using a wrench to unscrew a bolt.

larchmont

No, FDL.

Sheesh, I didn't think this was so hard to get across, but I guess it is.

So far, all we've gotten is:

(1) Elaborate scientific explanations; and
(2) Nice, plain-English answers which unfortunately aren't about cars.

What I think the original post asked for, and what I'd still like to see, is:

A simple, short explanation of what "torque" is, as applied to a car.

I took a swing at it:

My sense of torque is what I think TSXautoXer meant by "faster acceleration." I think of it as: how quickly and powerfully the acceleration begins kicking in when you plug for it.

But I don't have much confidence about it.

Is that about right?

If not, could someone try to give the correct, simple, one-sentence explanation?

fdl

I guess I should have read the entire thread, I only read your last post about wanting a very simple explanation.

As far as it relating to a car, well I think you pretty much got it. Torque is the force that accelerates the car, its what you feel, its what throws you in the back of your seat.

larchmont

Thanks, FDL.

Actually I did remember from physics (long long ago!) what "torque" means in a scientific sense. But when it comes to cars, which is what we're talking about, the term has a meaning that is far removed from that scientific meaning. (Related, of course, but far removed.) The elaborate explanations that we got here, while terrific, didn't help us understand the meaning in relation to cars any better than knowing that torque means "twisting force," which I already knew but which doesn't help us understand what it means about cars.

LeeLee

That's a very very dangerous way of thinking about torque, because someone is going to claim "Since torque is what accelerates a car, the TDI's 155 lb-ft of torque means it will accelerate faster than a B16A2's 111 lb-ft of torque!" when nothing is further from the truth.

Looking at crank torque is pointless!!!

Avoid comparing crank torque numbers like the plague!!!

Look at a HP curve instead!!! It's the one true salvation!!!

Santacruz

...not sure I agree that crank torque is completely pointless. In the case of towing or moving heavy objects torque is very relavent, no?

RogerPodacter

So how does the HP curve of the TSX stack up against other cars? Is the area under the curve good, average, poor?

LeeLee

In towing or moving heavy objects, good low end torque is necessary. In this case you want a torque curve that peaks early in low RPMs.

However, given two engines, one has 200 ft-lb of crank torque and the other 150 ft-lb. What conclusion can you draw? Absolutely nothing.

larchmont

Great, LeeLee -- I've been hoping you'd come in on this part of it!

So, why don't YOU give us the long-awaited answer:

In one simple sentence -- forget the physics and electronics, forget metaphors, analogies and all else -- what does torque mean, functionally and practically, as applied to cars (if not what I said, and which FDL said was just about right)?

Whatever you can say, I'd be thrilled.

If you or someone can't do something like that, the great great majority of us still won't get it any more than we do now.

(For whatever that may be worth!)

dnb

OK. So when accelerating from 0 to 10 mph, a car with copious low end torque will shove you back in your seat. A car with little low end torque will not.

DEVO

torque is never having to say you are sorry.

LeeLee

For the intended purpose of the TSX, which is a refined daily driver with excellent performance potential, the TSX's engine is excellent. Here is a comparison with some notable competitors:



Some warnings: this graph is meant to be a comparison of general HP curve shapes, and not absolute values. Although it confirms what we know about the three engines, differences in dyno equipment and environmental conditions make value comparisons rather worthless.

Anyway, here is my analysis:

Audi A4 1.8T - obviously a turbo-charged engine that waits for things to spool up at low RPMs, comes in strong mid-range, and then peter out dramatically at high RPMs. This graph shows why I find it so laughable for a turbo VW driver to claim a lack of low end power and torque for Honda engines.

BMW 325 - what a pretty graph. Smooth, linear, a solid line to the top. I like.

TSX - the surprise is the low end power curve that appears to be superior to even the BMW. There is no lack of low-end power here. Mid-range is also very strong, similar to that of the other cars. Top end has a bit of a hick-up around 5750 RPMs but continues to 7000RPMs with authority. It is the only engine not to taper off in power dramatically.

What we have with the TSX is a very nice engine, providing a constant delivery of power, with an HP curve that is at least as desirable as a BMW's I6.

LeeLee

As an engineer, this goes against my code of professional ethics and conduct, but I'll try

Wheel torque is the force that accelerates a car. All else being equal, a car with a higher peak torque number accelerates faster at low speeds.

There, I've said it. I feel dirty.:'(

Santacruz

so...torque is what gets the car moving and once the car is moving horsepower is what keeps it going?

LeeLee

NO! NO! NO!

See, this is what I am afraid of. As soon as I make a generalization on torque, people will base other generalizations off of it, with each generalization being further from reality.

Wheel torque is what gets the car moving and wheel torque is what keeps the car moving. However, to see how well things will accelerate with a torque curve, you need to factor in transmission gearing, wheel size, and etc. So even if you have a torque curve, you can't make any direct inferences to how well the vehicle will perform, especially across multiple gears.

Horse power cuts through the clutter and directly tells you everything. HP is good! It is pure! It is the one true salvation that will lead us to vehicular performance salvation. Cast aside your pagan beliefs in torque and follow the divine guidance of Horse Power!!!

Yes, torque is a good thing. Yes, more of it is better. And yes, you should ignore it and look at HP alone - it's far more productive that way.

Santacruz

AMEN MY BROTHER! I AM SAVED!! I have cast aside the unholy ways of torque and I am now baptized into the gosple according to HP. WHICH WAY TO THE CRUSADES!!!!!!!!!!

...I just need a little torque and I'll be on my way :devil: