Torque can permit you to work without any gearbox like on some large cargo boats.

Gearboxes don't like too much torque.

Again the fight of torque vs RPM..

No torque = no hp, no rpm. The actual physical property that accelerates the crankshaft is torque. Torque is a force, a vector quantity. Lift, drag and thrust are other examples of force. Power is not a force. Power is the rate at which work is performed; a scalar quantity.

I can bet than Stian should know the disction beetween a moment and a power.

From a point of view he's right. We don't care about torque. In cars, we just need power, whatever it is issued from any (torque,RPM) couple.

Confusion comes that torque is usually used in common language to exprime power at low revs.

Not possible. The acceleration of a wheel-driven vehicle is resultant to the thrust available at the drive wheels, obviously. The relationship between engine torque and hp relative to engine rpm is cast in stone. It is a simple matter to calculate drive wheel thrust from either power or torque. Both will produce the identical answer. If they do not, you are doing your sums wrong.

I care about torque. Without torque there is no rpm and no power.

The remark of Stian was not intended to tell the torque has no importance but the main characteristic of an engine is its power.

He could have made the same remark for top RPM.

But i think we loose our time. Most of folks, here, know the difference beetween force and power.


Main goals for competition are power curve surface during usable range, usable range, fast gear box.

Power curve surface is linear function of Torque curve surface. Then..

An engine is primary made to generate power (torque AND RPMs) , not pure torque.

That justifys to speak Watts for engines. Basically pilots and other drivers need Watts et each instant. They don't care about pure torque.

Basically, only engeneers and mecanics should be interested into get the details of Nm of RPMs to adjust balancing, designing, gearboxes.

Imagine two engines, both producing 100 horsepower, and identical shape torque curves (perfetly horizontal "curve" if you will, for simplicity): Engine A has 100 Nm, Engine B has 1000Nm. Both engines give exactly the same accelereration.
My last posting to this thread.

EDIT: To be back on topic: I've seen this "V10s will rule at Monaco" assuption everywhere. The V10s may give more punch lower down the rev range, but would it be an advantage at say, Monaco? Do they have to set the ratios significantly wider apart than on other tracks?

1 NM = .7375 ft-lb

100 Nm = 73.75 ft-lb

1000 Nm = 737.5 ft-lb
______________________

Engine A - 100 Hp - 73.75 ft-lb @ 7150 rpm

Engine B - 100 Hp - 737.50 ft-lb @ 713 rpm
______________________

In October of 1931, Caterpillar introduced the D9900. While the D9900 produced a whopping 89 hp @ 700 rpm and weighed in at 5,175 lbs (2352 kg), it would revolutionize the industry. That is why the original D9900 can be found in the Smithsonian today. This was also the first diesel engine to be equipped with air-intake filters. The original D9900 is still in working condition, it was last run in the 1970's for emissions testing (it passed).

So engine "B" is pretty much a 5,175 lb bulldozer motor vs a motorcycle engine.....I'm going to go out on a limb and say the bike is going to have better acceleration!

John

You call that 'going out on a limb'? You sneaked in power/weight ratio with those 2 comparisions. Please, don't try to confuse these guys with more math.

I think the average car driver would benefit more from information about Hp on diferent rev.
The only reason torque is listed in the informatio sheat you get at the car dealer is because there is some wanabee experts that think torque and low end power is the same.
To me a broad powerband is more important than information about pek hp and pek Nm.

I think GSX-R is among those that understand that

I guess the max torque value on specs should come from an old period.

Still today the max torque value permits to calculate that i know as "reserve of torque" ratio : [(max torque) / (torque at top power) -1] of an engine.

Reserve of torque on many engines as agriculture tractors can permit to estimate how an engine could react (in terms of loss of rpm) to an increase of the effort requested (slope of harder ground).
Until you're higher that max torque, you have a "reserve of torque".

Many many formulas have been imagined to describe engine skills. Noone replaces curves.

Because specs are often presented as tables, it could be a better idea to specify for cars the power at 2,000 rpm, for S.I and for example. For turbo C.I, max torque is a more interesting value in specs.

For not stationnary installation, nothing's best than power curve. Tables lie !

Regards
GS

Jeeze, I'm sorry......but I kinda had to......engine "B" would have to be a really big motor!

In any case, it's somewhat of a problem to generate an actual representative torque curve when you are only given two data points to start with.

John

PS......I wonder how much the chassis would have to weigh?

No offense but you are the one who is mistaken. It is perfectly accurate and technically precise to state that an "an engine has low-rpm torque." At any time, the force turning the drive wheels is torque. Power is not a force at all. Power is the rate at which work is performed.

If you prefer, you can say an engine has "good low-end power" but you are really only saying the same thing with an additional and unnecessary layer of abstraction. There are very good reasons engine manufacturers have rated engines in both power and torque for the past 100+ years. They are just beyond your view, that's all.

Honda S2000 2.0

177 kW at 8,300 RPM (204 Nm)
208 Nm at 7,500 RPM

Typical example where torque value really helps a lot to estimate low-end power

On the contrary, the torque@rpm spec points directly to the usual criticism of the S2000: its lack of low-end torque. Until the VTEC comes in this engine is a dud, and if you want to get anywhere you have to wind the piss out of the thing and shift a lot. It was actually designed in to large extent... to some folks jazzing the throttle and slamming gears is part of the "sports car experience." However, later models were retuned and regeared for better all-around performance and driveability.

You can call this quality a "lack of low-speed power" if you like, since the relationship between torque and power is mathematically set in stone, but the actual force that accelerates the car is torque. Power is not really a force at all. Power is the rate at which work is performed.

Meanwhile, there is no way to identify this trait of the S2000 from the max power @rpm spec. You could ask the automaker to supply a second power spec at some lower rpm... okay, what rpm? How about the rpm of peak torque? So what do we do then? Call it "power @rpm of max torque"? That's a little circular, don't you think? Why don't we just mean what we say and use max torque @rpm?

May be the S2000 produces 207 Nm at 1,000 RPM and can be considered as a torquy engine . At this point You don't know.
Basically, you can't guess just using this discrete information.

I think this is a case of the torque and, as a result, power curves being more important than the peak numbers.

Whilst engine A will have a thrust advantage at the top end, due to gearing, there must be large portions where it will have much less.

So tell me them why only car's and motorbikes has this data!
It's because the consumers think they nead to know.

B&W Man, Mak, RRM Bergen Diesel, Pielstick, Wärtsilä NSD(New Sulzer Diese) and so on don't provide torque data with there engines. They provide a powercurve.
It tels more about the caracteristics than peek power and peek torque the dealers hand you.

Sure, we would love to have a dyno chart for every engine. But peak hp @rpm and peak torque @rpm are the next best thing, and provide the bulk of the important info in much less space, only two lines.

These two data points provide a wealth of information: with them you can construct a fair approximation of the dyno chart, for example. From peak hp @rpm we can easily calculate torque at that rpm, and from peak torque @rpm we can easily obtain hp at that rpm. Now we have four data points and two trend lines. In the English hp/lb ft system the power and torque numbers will always be identical at 5252 rpm; there's a fifth data point.

Have you ever noticed that in F1, peak hp @rpm numbers are often leaked into the press, but the peak torque @rpm figures are much more closely gaurded? The hp numbers indicate the result of the engine program, but the torque numbers can reveal volumes about the engine development strategy itself. The torque curve is the engine's EKG.

Sure, you could assume that... if you don't know anything about engines. Here the power peak is at 8300 rpm with the torque peak only 800 rpm under that. That is more or less classic motorcycle engine tuning.

And if you examine the actual output chart for this engine, you will find a great big bump in both the hp and torque curves right near 6000 rpm, where the VTEC crosses over. Below that rpm, this engine is a dog. While the original S2000 had great performance on paper, it is a simple matter to blow off one of these cars on the road. Just catch him loafing in the wrong gear and cruise on by.

Actually, MAN does a pretty good job of presenting engine performance data......I like these guys!

Scroll down to the Performance Data!

http://www.mandiesel.com/R6-800_CRM_spec.htm

http://www.mandiesel.com/V8-900_CRM_spec.htm

http://www.mandiesel.com/V10-1100_CRM_spec.htm

http://www.mandiesel.com/V12-1360_CRM_spec.htm

http://www.mandiesel.com/V12-1550_CRM_spec.htm

John

Some engines could have their max torque at 4.500 RPM, let say 200 Nm for example and still 180 Nm at 2.000 rpm. Some other engines can get the same max torque@RPM and a ridiculous at low-end. We wannot always guess according our engine reading experience. New technology in volumetric efficiency, injection cartography, supercharging make this value more and more hard to extrapolate.

We can even suspect marketing sometimes to request to reduce the max torque@4.500 and makes appear the 180@2.000, not for some other manufacturers. Who knows ? So many problems with the interpretation nowadays that this value is often a trap. Altough i admit i read, it with frustration when RPM is above 3.000 rpm.

Marketing is marketing.

If Technology would always win over marketing, do you think we would use the operating system that is running on your pc ?

Difference in automotive and marine diesel is that there're so less marketing in the second. That's it.

Cars maker could easily put power/torque curves on their papers. It's not really "fashion" today.

Anyways, soon, you will just read mileage consumption information. Transmission will be continuously variable and will set the load engine / gear ratio based on the power needed and from the specific consumption charts stored into the memory of the computer. At this time max torque@rpm will be a memory. Power in case of dangerous situation will stay the ... prevailing value whatever the (torque,rpm) could be.

No, there is a big difference. A Marine engine runs at constant load -- doesn't even have an accelerator pedal, or need one. Automotive engines run unbder constantly varying load. What is the force that accelerates the crankshaft?

As for marketing...the purchasing decisions for commercial and industrial products usually involve millions of dollars, and people on salaries (often engineers) responsible for the purchasing decisions. They seek more comprehensive information than the retail consumer. This applies to engines as to everything else.

Have you ever been on a commercial cargo ship ? This can be run a different loads depending of the sea condition. Most cargo ships don't have any gearbox so power curve is also a criteria.


Force at ground is function of the power delivered by the engine not a function of the torque at the crankshaft !

What accelerate the more your wheels, an engine of 200 Nm@2,000 rpm or an engine of 100 Nm@5,000 rpm ? Torque or power ? What is the prevailing value for an engine ?

So if you want to be more concise, call it ... POWER !

Definitely torque is an obsession. You don't like RPMs..or the term power. I don't know


Thank you to repeat what i said about mass marketing for cars market.

People bash VTEC technology for lacking low end torque, for the wrong reason. How is 90% of max torque at 2k rpm equate to lacking torque? How is gaining <10% torque due to switching both cam profile and intake lenght equate to lacking low end torque? These people spread myth like it's a fact.

Power is a function of Torque and RPM. And thrust at the rear wheels is a function of torque and gearing.

As to the hypothetical...it depends on whether they are in teh same gear, or at the same speed.

If they are in the same gear 200Nm@ 2000RPM beats 100Nm@5000RPM, but if they are at the same speed then the latter wins.....because of gearing.

Forget the gear problem. This is a general case rule. Imagine you have ideally an infinity of gears and you can shift as quick as you want.

By the way, thrust at the wheel is a function of torque, rpm of the engine and ... speed

Thus you can reduce it at a function of just : power and speed. Gearing is "just" used to ajust the rpm of the engine according to the car speed to keep the power at a higher level.

When you can reduce an equation it's quite ridiculous to want to keep to use the discrete elements of it. That is why the prevailing characteristic of an engine will stay by the time its power, not torque. Because we use gearboxes and transmission and you will be able to exchange all the rpms you want into torque at wheel (at condition the engine can sustain the rpm you request for). That's it.

Remind driving feelings, why competition drivers ideally try to stay the most around max power rpm ? To get the max thrust.

Real case obvisouly takes in account the power curve, usable rpm range, car inertia, friction, drag, gearbox skills etc. But it seems someone would like to get into a basic physical discussion.

No, thrust at the drive wheels is a function of torque at the crankshaft. Thrust and torque are forces, vector quantities. Power is a scalar quantity.

The force you feel pushing you back in the seat is torque, not power. This is very easy to demonstrate with an accelerometer. Put your car in one of the middle gears, say second or third, floor the throttle and accelerate from a few mph up to the engine's redline. At the engine's rpm of peak torque, the vehicle's acceleration will be at its maximum. At redline the vehicle will be at/near top speed for that gear, and the engine will be at/near peak power, while the vehicle's acceleration will be at a minimum.

Here is a set of plots for a smallbore sports racer. Note:

1. From the first three charts, wheel thrust in each gear tracks engine torque.

2. In the third plot, note that at the vehicle's (aero limited) top speed, wheel thrust is at its minimum anywhere on the chart. (However, power at the rear wheels is identical in every gear.)

3. In the final chart for speed vs. acceleration, acceleration is greatest toward the bottom of each gear, while speed is greatest the top of each gear.

]

Basic incomplete assumptions.

This is torque at the wheel you feel, not torque ar the crankshaft. Because you have a transmission and the car is moving, torque at the wheel is function of the speed of the car and of the instant power of the engine (torque AND rpm if you prefer as i guess it for a reason i ignore)

I've just said you that power appears in the formulas to replace (Torque X RPM). Are you deaf ?

That is too shocking for you so then you prefer not to look to close at the formulas and discover for the first time that thrust is basically function of (power,speed).

Please let me know your formula of the force (newtons) that accelerates a car that could not be reduced to power and speed variables. It should be trivial. I'm very curious of it.

But maybe it's easier to insert nice coloured images. I don't know.

My 2 cents;
The mostest highest output in the solar system is the Sun. Its output, if I did the sums correctly, is 5.093X10^23 horsepower (not bad,eh?). Now, the Sun's rotation rate is approximately 2.671X10^-5 RPM. One can now calculate the Sun's torque , which is ~1X10^32lb-ft. So, is the Sun a torquer, or a top end power source? WPT

Do we have to debate this again. It doesn't matter.

You can calculate the thrust at the wheels by multiplying the torque value and finding the speed at which it is achievable by multiplying the rpm value corresponding to the torque value. If you do this mapping at each point from the torque curve you create the tractive effort curves and where they cross gives the optimum shift point.

Fat Boy was also right to point out that on a circuit and with finite ratios, this might leave you with a problem at certain turns if the apex speeds vary over a wide range.

I would always calculate the tractive effort curves from the torque curve as discussed and then integrate the resulting envelope to find the total power (force * velocity) under the curve - i.e. approach it from the point of view of maximising the G-G-V enevelope. If I was working for a team with a good budget I'd then use that as a starting point for a lap time simulation to optimise the ratios based on all sorts of other things, like circuit geometry, tyres, etc.

In the end - aren't we just discussing the difference between calculating things by force methods or by energy methods? Both are acceptable approachs surely?

Ben

More simple :

Force = Power / Speed

I wasn't trying to be offensive when I wrote this. I was just acknowledging the fact that you're going to say repeat 'Torque wins races' over and over without really explaining, in basic terms, what you mean. It's easy to come across wrong on a forum because there is no 'tone' of the speaker. I apologize if you found this offensive.

quote:
--------------------------------------------------------------------------------
Originally posted by Fat Boy


I did simulations to show that the actual acceleration of the car based on these engines was not going to be a based on the engine torque, but engine HP.

--------------------------------------------------------------------------------







Ahhh, Ben gets it.

You do not have to know anything about the gearing or the thrust at the contact patch of the tire if you approach the situation from a perspective of energy conservation. That's the advantage of thinking in this manner.

Example:

Given:
A car with a mass of m is accelerated with a average power of P for time T. At the begining of this period of acceleration, the car was at rest.

Question:
What is the speed of the car at time, T?

Answer:
The first law of thermodynamics, energy is always conserved.

K= the kinetic energy of the car at any point in time.

K(sub T) + K(initial) = P*T
K(initial)= 0, because the car started from a rest
K(sub T) = P*T

Assume only linear kinetic energy to make things easy. (but rotational kinetic engergy could be added if that information were supplied)

therefore: KsubT=1/2*m*V^2

1/2 *m*V^2=P*T

V^2=(2*P*T)/m

V=sqrt((2*P*T)/m)


So, there we have it. It's not what you would do at the racetrack, but you can calculate the acceleration of a car without knowing anything about the drive thrust at the contact patch. Having said that, this is not how I approach the situation in practice. The knowledge of this approach does, however, affect my view of the issue.

Intersting point, that is completely valid. Why torque is important to engine builders is because it corresponds to the total efficiency of an engine, like I said a couple pages ago. Mac is right, though. Perspective is the root of our disagreement, not the actual engine or gearing selection.

I was thinking about this yesterday and came up with an analogy.

Let's say you have the option of buying 10 shares of Stock A that is priced at $10, or 100 shares of Stock B that is priced at $10. You know that Stock A will double over the next year, and you know that Stock B will only rise 20% over the next year.

The 'efficiency' of Stock A is pretty amazing. Doubling your money is great, but at the end, your profit is only $100.

The 'efficiency' of Stock B is not nearly as spectacular, but if you choose that route, your profit at the end of the year will be $200.

If the end goal is profit and these are your only 2 options, you're going to take the stock that has a smaller percentage yield, but a greater overall payout, Stock B.

If Stock B only had a 5% return, though, then the effect of the 100 shares (RPM) would not be enough to overcome the 'efficiency' of Stock A, and your answer would change, you'd buy Stock A to recieve the higher profit.

One answer (i.e. 'efficiency' or '# of shares') does not cover all contingencies. You need to evaluate each particular case to see which has the best outcome.

Aren't we saying the same thing here?

Well, that's part of the disagreement and you are exactly right. As I said earlier in this thread earlier (post 54) as I have been saying in this forum for several years now, you can calculate from power/energy or from torque/ thrust perspectives and if you do not get functionally identical results from either you are doing your sums wrong.

However, in post 26 Fat Boy stated this is not so. He wrote: "I did simulations to show that the actual acceleration of the car based on these engines was not going to be a based on the engine torque, but engine HP." That statement is untrue. Just as you say, a vehicle's acceleration easily can be accurately calculated using either power or torque.

The rest of the controversy involves the failure to understand what power and torque are in the first place. For example, in post 74 GSX-R wrote, "Force at ground is function of the power delivered by the engine not a function of the torque at the crankshaft !" That statement is false as well. Force or thrust at the pavement is indeed a function of torque at the crankshaft; in fact the two are always directly proportional.

One benefit of having a torque/thrust chart close to hand... with one glance you can instantly see in which corners to expect wheelspin problems.

Wow, I think I'm finally beginning to understand the 'Torque Camp'. This is good stuff. I'm glad we have such good minds here.

How about back to the original question of the earlier thread:
Should you shift to maximize HP or Torque for fastest times?

or put it in another way:
Should you look at the HP or Torque curve to calculate shift points?

4 posts in a row, and I still missed addressing a point. In this particular case, the defense was grasping at straws. They were simply looking at peak numbers and ignoring how the engines would work in practice.

OK, here's how this went. Car A had a higher peak torque. Car B had a lower peak torque, but because of about a 25% advantage in usable RPM, it did have a power advantage. The engines were of different displacement and that was where the torque discrepancy came from.

When you set gearing in a racecar, you do so based off of the speeds you are going to attain throughout the lap. Let's say, Car A and Car B have similar top speeds (which they did). If max RPM in top gear was the same for both, then the difference in useable RPM will affect the gearing choices. Optimum gearing for acceleration to a given speed for Car A was different than the optimum gearing for Car B. Car B runs much 'shorter' gearing.

To use the 'thrust' view, the great RPM potential of Car B let gearing provide a greater amount of torque to the drive wheels which provided a thrust advantage which produced greater acceleration. To use the energy conservation approach, Car B was more powerful, and therefore able to expend more energy over a given period which produced greater acceleration. The conclusion was the same.

The case I was working on never went to court (we won). I was glad, because explaining the whole torque/power thing to people who weren't smart enough to get out of jury duty was going to be one hell of a head-ache.

Yes.

I've just said Force at ground cannot just be calculated from the engine torque.

bis repetita :

F (Newtons) = Power (Watts) / Speed (m/s). Apply it, test it. Check the unities.


Tell me if you find a simplest one. So simple you don't even know it.

Formulas save saliva. What's yours ?

That remembers me (among many other subjects) a thread where you were convinced that naturally aspirated diesel has a better thermal efficiency than turbo-diesel...( http://forums.atlasf1.com/showthread.php?threadid=86236) until really instructed folk like J. Edlund (among others here on this forum) confirm that.. After ?.. nothing.. no answer.. silence.

It seems you're periodically deaf, especially when you're wrong or when you do not want or don't have the real physic knowledge to understand what others are trying to explain to you. At this moment you stop to talk with the person that doesn't agree your explanation and look for possible allied guys.

Finally, the single truth here should be that you're always right. Too bad.

Gixxer,

Let's just talk about this stuff without getting too wound up, huh?

I sincerely would like to do so.

Gixxr. Your equation for force as a function of power is correct, but so is the following:

If I have an rpm and torque value from a torque curve the following applies:

Traction force @ road = (torque * gear ratio * final drive ratio * driveline efficiency) / tyre loaded radius
Road speed = rpm * (conversion factor to rad/s) / (gear ratio * final drive ratio)

Power in this state will be the traction force calculated * road speed calculated. I have used a force method and mapped the torque curve to give a tractive effort curve. You have used an energy method. We are both right.

BTW I find the force method nice because (as given in Fundamentals of Vehicle Dynamics by Gillespie) you can easily calculate an "effective mass" term to account for the driveline inertia. If you then add this to the vehicle mass and divide this total mass by the tractive force calculated you get a better estimate of vehicle acceleration.

It's a matter of preference as to which method you use, both are correct.

Ben

I agree Ben.

My last messages, you surely guessed, were destinated to Mc Guire (that lately indirectly talked to me) who definitely refused to admit we can express the Force (so acceleration) function using power & speed and this, as the simplest form we can do. My assertion was : if we could have a perfect continuously variable transmission as gearbox, so the prevailing parameter of an engine for acceleration is power, and not its torque. That was also in a certain way what Stian tried to explain to Mc Guire without any success. (post #56)

Sure, I will be glad to show you. OF COURSE you can calculate force on the ground from engine torque. If there is 100 lb ft of torque at the crankshaft, an effective gear ratio of 1:1 and the loaded tire radius is one foot, there will be 100 lbs of force at the drive wheel. It is just that simple.

No, you are totally mistaken. As I said in this thread a week ago in post 54: "It is a simple matter to calculate drive wheel thrust from either power or torque. Both will produce the identical answer. If they do not, you are doing your sums wrong." I have since repeated that several times here. Also refer to the infamous 20-page thread, where I repeatedly said the same thing several years ago.

Sure, with an imaginary fantasy CVT the engine can run at constant max hp rpm, and we never have to worry about accelerating the crankshaft. But in real cars with real transmissions, torque is important. What is the force that accelerates the crankshaft?