Relation between torque and effect. Why not linear?
 

Morning, guys!

Doc Fluffer here. Not posting much these days, but here is a question for you technically inclined.

As far as I remember from school there is a linear and direct relation between work/torque and effect. The former measured in Nm or J and the latter measured in W or horsepower. Time (s) being the third denominator. I hope I remembered that correctly.

That would imply a direct and linear relationship between torque and horsepower in a car engine.

Now, what are the factors in an engine the affect the disruption of this linear relationship? Typically a big diesel truck engine makes a huge torque with a relatively moderate bhp output, while a small race engine develops a lot of horsepower but, conversely, a modest torque.

Is it the volume of the engine? Gear ratings? Density/weight of different engine components? Other things?

Also, where in an engine is torque measured?

I have tried to grasp this particular questions since I was a teenager. Alas, so far, no cigar. Anyone able to explain this so I understand it will get a wild card for free fluffing a whole year.

Thanks! :)

Torque causes movement over a distance which is work. Power is the time derivative of Work. Torque is like a force (here it is a force x distance so Newton-Meters or Pound-Feet). Work is that Torque being applied to a load, integrated over the whole distance (degrees or revolutions) that load travels. Think of pushing a rock up a hill.

Power is how fast the Work is done. It is dW/dt (time derivative). dW/ds (distance derivative) is Torque.

Basically, what you want to know is that:

Torque x engine speed (rpm) = Power

Torque x # of revolutions total = Work

Torque is measured on a dynomometer by putting a load on the engine (usually a water brake) and seeing how hard it can turn. Since they cannot stall the engine without stressing it too much, they apply a moderate load and measure how fast that work is done to get power.

When you multiply torque by the rpm it is achieved at, the graphs look like they do.

As with basic calculus, the derivative of x^2 is 2x and the derivative of 2x is 2 so a constant torque would yield a linear power slope...

basic calculus and physics.

By the way, in the USA, Horsepower = (lb-ft x rpm)/5252

Brilliant! Thanks a lot, Flieger!

I will have to read your post a few times and see if I really grasp the essentials. Being a tech ignorant its very frustrating trying to comprehend interesting matters when it just won´t compute upstairs.

Typically a big diesel truck engine makes a huge torque with a relatively moderate bhp output, while a small race engine develops a lot of horsepower but, conversely, a modest torque.

Is it the volume of the engine? Gear ratings? Density/weight of different engine components? Other things?




Yes, torque is proportional to displacement, about 80 ft/lbs per liter N/A tops. Horsepower is just an abstraction, it is not measured, it is calculated by multiplying by rpm. That is how a 2.4 ltr F1 engine can have 800 hp. When you multiply by 18,000, things happen. Peak torque in an engine occurs at the VE peak, when the engine inhales the highest percentage of its displacement. Raise the VE, the peak torque rpm goes up, the calculated horsepower goes up

Thanks!

Given that torque x rpm = power, why does the latter tend to drop off in a graph at the end of the curve? It would seem an engine has a peak power (and torque) at a certain rpm and higher revolutions per minute will not gain any more, rather the opposite. Why is that?

Because the torque is dropping faster past the peak. Try looking at some hp and torque charts. Hp=torqueX rpm/constant(5250). Hp almost always peaks above the peak torque rpm and the lines cross at 5250. The torque curve is a proxy for VE, it starts out low and climbs to the peak (say 90%), then drops off, sometime dramatically, after the peak torque rpm. If you can keep the slope of the torque drop low, you will make more power. Engines with fixed valve timing must balance low speed performance with high rpm breathing. Engines with ideal valve timing for high rpm breathing are lousy performers at low speed. Variable valve timing was invented to improve the compromise. You can pretty much tell an engine's power band by focusing on when the intake valve closes.

Thanks, Paul. That is very informative and interesting reading. I wish I could learn more about the basics of engine "physiology". Can´t seem to find any appropriate literature however. Its either too basic or far too comprehensive.

hp = torque * rpm * constant

because rpm and torque are multiplied the net effect depends on the relative slope of the 2 curves.

rpm always has a + slope(ie goes up from left to right), torque slopes vary depending on whats going on inside the engine, they will be very + at points where the engine is working harmoniously inside, less + as things get out of sync and also go - when inertia catches up to gas flow volumes

what's happening in side all the cylinders collectively determines torque #s. The most torque comes from having the most massive fuel/air charge compress and burn most efficiently/completely in the right time window, this generally is easiest to accomplish at lower rpm. The diesel runs at low rpm and has minimal intake restriction and high compression ratio compared to a gas engine hence it's high torque.

when there is a wide rpm range it is harder to optimize torque at all points so w/o using variable geometry engines(to keep it simple) torque is optimized at a single point in the rpm range. If the point is down low you have a torquey engine, think truck or family sedan, if the point is up high you have a sportier engine used in a sports car, higher yet and you have a race car

w/i an individual cylinder there are many factors that determine the mass of the fuel/air mixture to be burned. The biggest is the available time during which the intake valve is open, the pressure differential between the intake manifold and the cylinder and the resonances/flow patterns that are occurring. At high rpm there is simply less time for the cyl. to fill so the torque curve tends to flatten then drop as rpm increases but the resonances in the intake and exhaust can be used to increase the mass of fuel/air charge at very specific and limited rpm points. If a variable geometry is used(vari ram & vari cam) the mass of fual/air charge ingested(volumetric efficiency) can be raised over a much wider rpm band

When both slopes are + hp goes up fastest, when one is positive and the other less so, hp increases at a slower rate, when one is more positive then the other( even if the other is -) hp can still go up but more slowly, when one is more - than the other is + hp goes down

small torques are amplified by gearing, gearing includes the transmission gear sets, cwp and tire dynamic loaded radius


depends on the measuring tool
a chassis dyno measures at the rear wheels or hubs in some cases
an engine dyno measures at the flywheel

Wow, thanks, Bill!

Just found your post above. I think I will put my Norman Mailer book aside tonight. This is all good reading.

Thanks a lot, everyone!

BTW - Power is the time derivative of Energy, not Work...

also Marcus, it is easy to get an intuitive understanding of torque

- find a shaft that is spinning and grab it - how hard it is to stop the shaft (or slow it down) relates to the torque

I must disagree. Power is how fast work is being done.

However, the change in an object's kinetic energy is equal to the total work done on it (assuming no frictional losses), so work and energy are very close.

work and energy have exactly the same units, and are closely related concepts
power is the rate at which work is done and includes an additional time element in the denominator which is not found in the other 2 quantities.

dimensional analysis shows what are equivalents and what are not
dimensionally
work - ML^2T^-2
energy - ML^2T^-2
power - ML^2T^-3

Thanks again, everyone. I have read all your posts repeatedly. I grasp the general laws of physics applied here but I am still curious as to what are the specifications in an engine that tends to give it relatively higher torque vs effect given a certain rpm.

As Randy mentioned, torque is what makes it difficult to stop a cylinder from rotating - is momentum a proper term in English? If so, what characterizes an engine with relatively higher degree om momentum? I instinctively suppose the general size of the engine, but specifically what parts? Or is that a mute line of questions?

Still confused but on a higher level. Thanks!

What do you mean torque vs. effect? By effect do you mean power?

An engine with little torque can make loads of power if it spins fast- like a sportbike or an F1 car.

Torque comes about by two means. Inertia torque and gas torque. Gas torque is the actual force due to the combustion pressure. Inertia torque is the torque that remains after the combustion has stopped and is due to the momentum of the system. A heavy or large diameter flywheel has a lot of inertia and therefore lots of angular momentum. The reciprocating pistons and the rods travelling in general plane motion also have momentum and cause a force on the crankshaft because impulse = change in momentum. Impulse is force times time. The force varies with the orientation of the crankshaft throw and the changing leverage.

At high rpm, the inertia torque dominates the gas torque and this is where a properly balanced crankshaft really shines in smoother running. At low rpms, gas torque dominates and the firing order is more important.

Because of these effects, Yamaha used a cross-plane crankshaft in its YZF-R1 sportbike with its inline 4. The firing order is crazy uneven so it fives up some top end horsepower. At mid-throttle openings, the power is smoother, though, because the gas and inertia torques are more balanced. This does not overwhelm the rear tire and allows smoother drives off corners and wears tires less. Ducatis with a big L2 have a big bang firing order which makes huge torque and then goes quiet for a revolution to allow the tire to catch up. Sort of like pumping the brake pedal to stop lock-up. They are notoriously hard to ride but have crazy top-end horsepower.

Some race riders can feel the Yamaha's lack of agility, however. It is due to the necessary heavier, stronger crankshaft which has more inertia, angular momentum, and therefore a greater gyroscopic stabilization effect on leaning the bike through a turn.

Great post! Thanks!

Is it generally fair to claim then, that if two engines spinning at the same rpm with identical torque will have the same power output (bhp) and raising the rpm will continue to produce the same output.

You see, my original confusion is related to the fact that I read a whole lot of torque and power specifications about different cars and I always wonder why two cars with the same power output can have very different max torque numbers and vice versa. Is that all depending on at what rpm you measure the output?

I am really sorry to bother you guys with these stupid questions. I am a slow learner (and driver).

Thanks!

hp = torque * rpm * constant

to keep it simple lets ignore the constant and units, we will compare 2 engine w/ exactly the same maximum torque, say 100
but engine 1 makes max torque =100@2000rpm and engine 2 makes max torque =100@4000

engine 1: power = 100 x 2000 = 200,000
engine 2: power = 100 x 4000 = 400,000

remember we are ignoring all units and the constant so the #'s are for comparison only
also remember that each engine has a torque curve at rpm above & below the indicated ones.

what will the percieved difference to a hypothetical driver?

engine 1 will have a lot of low end grunt it will pull strongly, gearing will only add to the pull, it will have a relatively low top speed unless the gearing is highly overdriven, this sort of engine doesn't need lots of gears 4 or 5 is fine

engine 2 will have relatively poor pull down low but w/ proper gearing can be made to pull through out the rev range as gearing is a multiplier of torque, the more gear choices the better ie 6spd is better than 4

It is better to have torque high in the rev range because then you can take advantage of it w/ gearing

Now you can make a fast diesel as Audi has done by having lots of torque at relatively low rpm but then using lots of overdrive gears, but by far the more usual race engine strategy is to make torque at higher rpm then gear it to suit.

Thanks Bill! I think I start to understand the concept.

This is not news to me, but worth repeating. The comprehensive knowledge and insight around here blows my mind. You guys are absolutely Impressive.

Dare I ask one more question. Along the line of Bills post above, what factors will decide at what rpm an engine develops max torque?

what factors will decide at what rpm an engine develops max torque?

Valve timing, intake length, valve curtin area/displacement, and port size. Experiments in the 1950's determined you could manipulate the torque peak (lower it) by increasing the length of the intake tract out to 33 inches, with the trade off of sharply lower high speed torque. Every intake length has an rpm (frequency) where a positive pulse returning to the intake valve will boost VE. This is the principle behind multiple length intakes.

If you want to understand torque, focus on the fact that torque is proportional to displacement. Regardless of the design or parts, torque output is limited to around 80 ft/lbs per liter. The only way to exceed this is to pressurize the intake.

Much of engine design history is distorted by artifical displacement limits and tax laws. We were racing 15 liter engines until the 3000 rpm limit was broken in 1912. Speeds rose so fast, displacement limits, first 5 liters, then 3 liters, then 2 liters, then 1.5 liters, all in the span of ten years to keep the drivers alive. The small displacement high reving engine for a road car is far from ideal. The ideal engine for a 4 person road car looks something like a 5 liter V-8 with variable cylinder deactivation, +35% EGR and a turbocharger. Two liter economy and 8 liter torque.

Thanks, Paul. Good pieces of information. I start to think I am on my way to comprehend the basics.

The 3.2 Euro Carrera put out 231 bhp. The rev limiter was set at about 6250 rpm. Now, the Club Sport edition was blueprinted and the rev limiter was raised to around 6800 rpm if I remember correctly. PAG claimed no power gain but allegedly these engines had an output around 240-245 bhp.
Anyway, as the peak power was reached significantly below the higher set rev limiter, why raise it at all? What am I missing?

What am I missing?

You are now on an other topic, gearing. This is a difficult issue and even the smartest people I know, aircraft engine designers and Phd astrophysicists among them, are willing to debate some things gearheads take as given. It think it may involve Zeno's paradox, so beware the simple explanation's.

There is usually an acceleration benefit to exceeding the hp power peak rpm before shifting, even though power is dropping. It has to do with the torque delivered after the shift at the higher rpm.

I think the Club Sport also had different valves and springs and fewer parts at a higher price, so a good business as well.

Livi,
You are missing the idea of leverage (in this case gearing). The ability to multiply an engine's torque by greater leverage (that is being able to remain in a lower gear) can increase your forward thrust and thus acceleration.

Most engines only hit peak torque at one spot in the rpm band, but that doesn't necessarily make the rest of the rpm band useless. Safely broadening the rpm range can increase forward thrust.

Doug

OK. Thanks, everyone. I think I am hovering slightly closer to understanding the basics. I also understand that I am covering a very shallow area of this very complex story. Trying to simplify what is really much more comprehensive and difficult.

Revs are the meat that feeds gearing

here is a comparison of the relatively minor change in tire height and how gearing magnifies and feeds on it

the y axis is the actual thrust pushing the car forward, it is the net result of the engines torque multiplied by gearing
http://forums.pelicanparts.com/uploa...1233949448.jpg



here' another for my 993 w/ the powerband highlighted, you always shift because the engine runs out of revs, this one is comparing a street trans g50/20 and a pure race trans g50/30
http://forums.pelicanparts.com/uploa...1199227901.gif

These are not stupid questions!

Maybe some of these will be interesting. Flieger's explanation is pretty good though. I always like looking at equations in physics. Hopefully I don't add to the confusion.

Work = F*d*cos(theta)

Here force (F) acts on some object over a distance (d) and at some angle (theta), this angle between the displacement (an object's "trajectory"/"momentum direction") and the force vector(s) applied. If you are going north, then someone applies a force on your car going east, they have done NO work on you going north. The angle is 90 degrees. They only did work on you in the East direction! Now, if you ask how much work they did on you in the East direction, it is simply W = F*d because the angle between East and itself is 0 degrees, and cos(0)=1. [Please pardon me switching between radians and degrees here .]

Work is not energy, although the Work-Energy principle states that Work and Energy are exchangeable. Work is a change in Energy (E) in any chosen direction/reference frame. If you are driving along, your car has a certain amount of energy (kinetically). If you then press the brakes, the brakes are doing work on the car, reducing the amount of energy you have kinetically. The energy you removed from the car kinetically is changed into heat energy, and dissipated into the environment through the rotors of the brakes.

Power is a change in Energy over time. Watts for light bulbs is Joules (energy) per second. How much energy change over how much time. So, power is like Work/time.

Energy is defined in lots of ways, but kinetically,

K.E. (Kinetic Energy) = (1/2)*m*v^2

So, a car that weighs 1200kg going 50 m/s has .5*1200*50^2= 1,500,000 Joules of Energy

There is a rotational analogue to Kinetic Energy:

K.E.(rotation) = (1/2)*I*(omega)^2

Notice how the rotation equation looks almost exactly like the one above!

I is an inertial component, like mass is--its resistance to being moved--times the speed with which it rotates.

If you spin an engine very fast, you can see the energy of the assembly goes up very quickly, because it is being squared! One radian is 2pi. If you complete 2pi*18000revolutions in 60 seconds, the omega = d(theta)/dt = 1885 radians/sec. Square that number = 3,553,225 . You can see how spinning something faster greatly increases the energy of that thing!

Torque = F*d*sin(theta) [or r CROSS F sin(theta), which also tells you the direction of the torque vector ; I won't get into that here.]

Torque is a bit more complicated, but similar. You have to think of it as a rotational analogue of some other fundamental basis of classical mechanics. We already have the concept of momentum, P=m*v, or simply, momentum is just something's mass (m) times its velocity (v). Now, think of angular momentum, where some rotating thing has a certain component of weight (a force) and a certain component of velocity going in a circle. A special case of angular momentum is

L=I(omega).

I=.5MR^2 for a disk. Its moment of inertia in angular momentum is determined by 1/2 its mass times its radius squared. Omega is like velocity -- change in distance over change in time -- only now omega defines a change in angle around a circle per unit time. omega = d(Theta)/dt

If angular momentum is defined as L, then Torque is the change in L over a change in time: dL/dt -- the infinitesimal change of angular momentum related to an infinitesimal change in time.

So, "inertial torque" is a torque that is a product of the fact that a crankshaft has weight (mass x acceleration of gravity it experiences).

Now we see two distinctions:

-Torque is a change in angular momentum over time.

-Power is use of energy over time.

When you abruptly rev up the engine, the fuel applies a force at a distance from the crank, which is a torque. It adds angular momentum. Now, you could add a lot of angular momentum, just by applying a huge force. Imagine sticks of dynamite in the combustion chambers. They would apply a very quick, large force to the crankshaft (if they didn't blow the engine to pieces), and this would mean the dynamite exerted a large torque on the crank. But that doesn't mean the engine is spinning fast now; it means it is spinning "strongly" now.

A diesel is torquey because it applies large forces, using compressed fluid (air-fuel with turbocharger), dense fuel and high compression. Each explosion exerts a large force on the piston, but that doesn't mean it spins fast.

A torquey *AND* powerful diesel engine would be one that is volumetrically efficient at high engine speeds, meaning it can flow enough air to keep the engine running at a high speed, and still provide a forceful charge at that speed to generate a large torque.

Did that answer your questions?

Here I'll try to address it directly:
"Is it the volume of the engine?
No-it is about the volumetric efficiency of the engine. At its highest V.E. point, the engine will be able to make the best explosion--the highest force--the most torque. However, torque, as shown above, is a derivative of a linear function d/dt[L=I(omega)], while power is a derivative of a quadratic function, d/dt[KE=.5I(omega)^2]. Notice if you take d/dt[KE] you get L! d/dt[.5I(omega)^2 = I(omega) ]

Gear ratings?
Has nothing to do with measurements of power/torque.

Density/weight of different engine components?
Of course the weight definitely has a torque, because it exerts a force (mass*gravity) partially in the rotational mode. Heavy, lumbering engines are better at keeping trucks going when you let off the gas, compared to, say a superbike engine in a lorry.

Also, where in an engine is torque measured?"

Torque is measured like Flieger says. It's based on a calibrated friction disc ("torque plate"). If a dyno tester is rated to 1500 lb.-ft., it implies that there is a distance from the center where that is calculated. Torque= r X F , r is the distance from center and F is the force applied.

Now, I have to thank you for stimulating me to write this out ! I am so happy you forced me to recall Classical Mechanics and hopefully explain it ... :)

this got neglected I think... momentum is a proper term in English, it is the product of the mass and velocity of an object; p = mv

things tend to keep moving once they are moving & they tend to sit still until acted on by an outside force

livi, I think you would enjoy reading a book that is some sort of introduction to how IC engines work - I don't know of one, but maybe somebody can post a title...

There is also a nice book by, IIRC, Phillip Smith "The Design And Tuning Of Competition Engines." It is early post WWII and out of print. You could buy a used copy or get it from your library via ILL. a bit more advanced but not an engineering text by any means.

Ytnuklr points out why I always think of power as being the time derivative of energy...

Now, you can think about an engine as an air pump - if you pump more air, you get more oompah. So, how can you do that?

- bigger cylinders
- more cylinders
- spin everything faster
- supercharger
- turbocharger
- design the motor for better airflow - aerodynamics apply inside the engine, right?

No one mentioned the frictional forces inside the engine yet, but they can be troublesome. For any given displacement, there is a certain # cylinders that is a sweet spot (optimum) - very tiny V-8 motors have been built (most recently by a Japanese co.), and gigantic 1 cyl. engines have been built ("thumper") but they are more design exercises usually. Also, as technology advances, you can reduce the frictional losses inside an engine, so more cylinders could be used at smaller displ.s

Then there are pumping losses - one reason to use a dry sump...

Design criteria for motors also include ease/cost of manf. (and one would hope, of repair), fuel consumption, emissions, and packaging constraints. Porsche has generally lowered the profile of the 911 motors and the ht. of the rear shelf in a 996 is substantially lower than in the air cooled cars. Same thing for VW Buses/Vanagons.

So, I hope that helps. If not, I hope it at least obfuscates everything sufficiently that you have all forgotten the original question.

How wrong you are. Notice the differences in the curves above, that same difference would be plotted if the graphs were wheel torque instead of thrust


again it is worth repeating

100ft-lb of torque at 1000 is not the same as 100ft-lb @4000 because gearing can change the latter into acceleration very easily. You would need 400ft-lb @1000rpm to match it. It is far easier, lighter and economical to generate the 100ft-lb @4000rpm and the drive train to go w/ it than to generate 400ft-lb @1000rpm and the drive train to go w/ it


you can get bogged down all day w/ the underlying math, but that doesn't get to the heart of what was asked.

torque is just the twisting force which the crankshaft delivers to the clutch, from there gears/tires do the rest

also to repeat torque can be measured in several ways
1) engine torque is measured on an engine dynomometer, this gives what is called brake torque because the engine is run against a load that brakes the engine, the load is usually hydraulic but it can also be electromagnetic
2) wheel torque is measured at the wheels on big rollers again the rollers are hydraulically or electromagnetically braked to load the engine sometimes the rollers are not braked in that case there known mass is used to determine how long it takes to spin them to a specified rpm this is called an inertial dynomometer and is the least useful tho most common type found. It is least useful because you can't hold the engine at a given steady state rpm as w/ other types
3) hub torque is measured by attaching the dynomometer brake to the wheel hubs, I like this best for us amateurs because it eliminates the tire friction w/ the dyno roller as a variable and is far easier to use as you don't need to pull the engine to do a test run(and incidentally you can see the measured difference in torque in each gear)

This is correct.

Forgetting how a motor actually operates and using a typical (rpm) x (HP&TQ) graph, the following would hold true.

If you piloted TQ in a straight line by rpm (say fixed at 100 ft lbs from zero to red line), HP would be a straight line increasing by rpm.

Then, if you piloted HP at a straight line (say fixed at 100hp form zero rpm to red line), TQ would be in a straight decreasing line. It would be highest at zero rpm and lowest at red line.


Now, if you plot TQ on a curve like with a typical motor, as long as TQ is increasing HP is increasing

Also, as long as TQ is decreasing but at at a 'rate' that is less than rpm's are increasing, HP will climb. Example, if TQ is decreasing at 10% and rpms are increasing at 15%, HP will be climbing.

At the point where TQ falls off at a rate equal to the rate RPM's are increasing, that is typically where HP flatens and peaks. Example, if rpms are increasing at 15% and TQ is decreasing at 15%, the HP line will be flat.

When RPM increase at a rate faster than the rate TQ is falling off, the HP curve will start to fall. Example, if rpm are increasing at 15% and TQ is decreasing at less than 15%, HP will be falling off.

----

The point where a motor is at its most efficient point of operation and making the most power with each stroke, is where TQ peaks.

The point where a motor is at its most total power is at its HP peak. This is where increases in RPM can no longer make up for the rate TQ or efficiency is falling off.

Also, as long as the rate RPM's are increasing is more than the rate TQ is falling off, the motor's HP curve will continue to climb.

----

Further:

It takes twice the TQ at half the RPM to make the same HP.

It takes half the TQ at twice the RPM to make the same HP.

Move the TQ curve to the right 10% and HP will increase 10%.

Obviously, gear ratios affect the thrust you feel in a car. Duh. Gear ratios and tires are range multipliers/reducers, sure, for the operating range of the engine. But we're talking about engines by themselves. I'm not wrong on that. If this were the case you would say things like, "my engine has 1000 hp...as long as you use X and Y gear ratios." I think you are talking about acceleration, which has other considerations like tires, gear ratios, etc.

I think the gold mine in this thread is this, slightly reworded but expressed by 911st:

The point where a motor is at its most [volumetrically] efficient point of operation and exerting the largest force upon the pistons, is where TQ peaks.

The HP peak is where increases in RPM can no longer make up for the rate TQ or efficiency decreasing.

That's as simple as it gets, and no simpler, I think. Einstein would be proud.

Well said Scott. I can get wordy. Thanks.

Acceleration is at its highest at HP peak.

Increase your averagee HP and you have a faster car.

You can do this by increasing your total HP.

Or, you can also do this by having closer gears so you spend more time at a higher power levels.

For example, say you shift into second at 50mph near red line and that puts you at say 4500rpm where you are making 200hp. If you put in a shorter second gear that lets you come in at say 5200rpm where you are making say 230hp, your average HP will be higher and you will be faster.

Please forget the handed down sayings about gears, they will only get in the way.

What gears do is have a direct effect on what point on the HP curve you operate and thus your averagee HP'.

The car that operates at the highest averagee HP is going to get there the fastest.

One more way to measure torque.....strain (twist) in a shaft can be measured without contact with the shaft...(magneto elasitcally)

ABB's Torductor S is used in F1 and engine / transmission development by OEM's to measure torque (and in F1 tune EFI) in real time.

This will find its way to production cars in the next few years (driven by the need to minimise emissions)

ABB Torductor PDF

How it works...for the technically minded US Patent 6532832

http://forums.pelicanparts.com/uploa...1273186841.jpg

Here is one for you.

The more TQ you can make, and at a higher RPM, the more HP you make. (Lets call this TQ-1)

The more HP you make and the gear ratio you operate at determine your rear wheel TQ. (say TQ-2)


TQ-1 and TQ-2 are both Torque. But they are not the same Torque.

For example, a diesel car could have twice the TQ-1 as a gas car (but at about half the rpm) and they could be operating at the same torque level measured at the rear wheels (TQ-2). Thus, different motor torque values can equal the same wheel TQ.

Please try to forget all the hand me down sayings about Torque you have heard. Things like a transmission is a Torque multiplier, we want to come in at TQ peak when we shift, and it is TQ that accelerates a car.

All these are based in truth if applied correctly and to a different degree, however they will only get in the way for most when trying to understand if TQ or HP or Power is what makes us fast.

The highest average HP a car can maintain at the lowest car weight will make for the fastest car acceleration.

Just my two cents.

911st, you just made a case that TQ is useless; only a by-product. Or, am I missing something?

And, yes, I'm the bunny with a pancake on its head when is comes to the theories presented in this thread.

you got off to a good start, but just a restatement of what was previously stated


wrong wrong wrong

torque & rpm are the only things that are important, torque at high rpm makes for high hp and faster acceleration

again going back to my previous comparison
400ft-lb @ 1000 rpm is the same hp as 100 ft-lb @ 4000rm but the first will make a great truck engine and the second a better car engine

hp is derived from the product of torque & rpm and is sort of useful in describing the nature of an engine, but make no mistake about it torque is what pushes a car down the road

current transmissions are torque multipliers, it is just a matter of how much the torque is multiplied, each gear is different

yes, there is a difference between flywheel torque and wheel torque, the difference is simply the amount of multiplication done by the gear sets, cwp & tires

Torque is the starting point and with out it there is nothing.

However, it needs its multiplier, RPM, to make HP so it can reach its potential.

The more TQ and the more RPM, the more power.

Big Torque dose not necessarily mean big power or acceleration.


For example we could take three power plants.

A gas V8 that makes 500 lbs at 5200rpm TQ and 500hp.

A Diesel truck motor that makes 700 lbs at 1600 rpm and 400hp.

A steam engine that makes 2000 lbs of torque at 100rpm or 38hp.

Put each in a truck weighing 5500lbs with the perfect 6 speed transmission for the motor and it will most likely be the motor with the most HP that is the fastest and the one with the most TQ that is the slowest.

However, make big TQ at big RPM and you have really big HP.

No, torque and rpm are what is important for performance, hp is derived

hp = (torque x rpm) x constant
torque is in lb-ft
rpm is self explanatory
constant is 2pi/33000

Bill,

You left out or missed my statement that followed my suggestiong that people try to forget the hand me down sayings so that they do not get hung up on TQ.

Yes, TQ and RPM make power.

I did restate the same thing many different ways hoping someone might hear somthing in a way that sticks.

I think we are saying the same thing, but that my wrighting sucks.

I think maybe HP is 'the result'.

I am thinking the 'constent' is nothing really except agreeing on the size of the horse.

Let's try one more for the uneducated: What is the definition of the "power band?"
IIRC, when setting up a trans for a particular track, you want to keep the revs within the PB as you make your way thru the gears and around the track. So, if not going below max TQ when upshifting, what is the goal?

And why?