Buger

Oh My!!!

Every self respecting automotive forum has to have several horsepower/torque threads right? This has been discussed numerous times here of course but perhaps it's time for another thread on the topic since the subject seems to keep popping up in other threads.

Buger

One link that does a good job of explaining things is:

http://www.vettenet.org/torquehp.html

I originally posted the link here over half a year ago but perhaps now is a good time to post it again.

Below is from that site:

Torque and Horsepower - A Primer
From Bruce Augenstein, rba@augenstein.ultranet.com
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There's been a certain amount of discussion, in this and other files, about the concepts of horsepower and torque, how they relate to each other, and how they apply in terms of automobile performance. I have observed that, although nearly everyone participating has a passion for automobiles, there is a huge variance in knowledge. It's clear that a bunch of folks have strong opinions (about this topic, and other things), but that has generally led to more heat than light, if you get my drift :-). I've posted a subset of this note in another string, but felt it deserved to be dealt with as a separate topic. This is meant to be a primer on the subject, which may lead to serious discussion that fleshes out this and other subtopics that will inevitably need to be addressed.
OK. Here's the deal, in moderately plain english.

Force, Work and Time
If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on.
In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time.

Awhile back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower.

Everybody else said OK. :-)

For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms which define a *twisting* force, such as foot pounds of torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum.

Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.

Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidently, we have done 6.2832 foot pounds of work.

OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement:

.................. Torque * RPM
Horsepower = ------------
........................ 5252

This is not a debatable item. It's the way it's done. Period.
The Case For Torque
Now, what does all this mean in carland?
First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.

You don't believe all this?

Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-)

The Case For Horsepower
OK. If torque is so all-fired important, why do we care about horsepower?
Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.

For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-).

On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:

6 HP.

Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.

At The Dragstrip
OK. Back to carland, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you :-).
A very good example would be to compare the current LT1 Corvette with the last of the L98 Vettes, built in 1991. Figures as follows:

Engine Peak HP @ RPM Peak Torque @ RPM
------ ------------- -----------------
L98 250 @ 4000 340 @ 3200
LT1 300 @ 5000 340 @ 3600

The cars are geared identically, and car weights are within a few pounds, so it's a good comparison.
First, each car will push you back in the seat (the fun factor) with the same authority - at least at or near peak torque in each gear. One will tend to *feel* about as fast as the other to the driver, but the LT1 will actually be significantly faster than the L98, even though it won't pull any harder. If we mess about with the formula, we can begin to discover exactly *why* the LT1 is faster. Here's another slice at that formula:

........... Horsepower * 5252
Torque = -----------------
..................... RPM

If we plug some numbers in, we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @ 4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed, and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and anybody who owns one would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point.
On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm, and is happy right up to its mid 5s redline.

So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occuring a little earlier in the rev range, but that is debatable, since the LT1 has a wider, flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid range and up, however, the LT1 would begin to pull away. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT1, by definition, has an advantage.

Another example would be the LT1 against the ZR-1. Same deal, only in reverse. The ZR-1 actually pulls a little harder than the LT1, although its torque advantage is softened somewhat by its extra weight. The real advantage, however, is that the ZR-1 has another 1500 rpm in hand at the point where the LT1 has to shift.

There are numerous examples of this phenomenon. The Integra GS-R, for instance, is faster than the garden variety Integra, not because it pulls particularly harder (it doesn't), but because it pulls *longer*. It doesn't feel particularly faster, but it is.

A final example of this requires your imagination. Figure that we can tweak an LT1 engine so that it still makes peak torque of 340 foot pounds at 3600 rpm, but, instead of the curve dropping off to 315 pound feet at 5000, we extend the torque curve so much that it doesn't fall off to 315 pound feet until 15000 rpm. OK, so we'd need to have virtually all the moving parts made out of unobtanium :-), and some sort of turbocharging on demand that would make enough high-rpm boost to keep the curve from falling, but hey, bear with me.

If you raced a stock LT1 with this car, they would launch together, but, somewhere around the 60 foot point, the stocker would begin to fade, and would have to grab second gear shortly thereafter. Not long after that, you'd see in your mirror that the stocker has grabbed third, and not too long after that, it would get fourth, but you'd wouldn't be able to see that due to the distance between you as you crossed the line, *still in first gear*, and pulling like crazy.

I've got a computer simulation that models an LT1 Vette in a quarter mile pass, and it predicts a 13.38 second ET, at 104.5 mph. That's pretty close (actually a tiny bit conservative) to what a stock LT1 can do at 100% air density at a high traction drag strip, being powershifted. However, our modified car, while belting the driver in the back no harder than the stocker (at peak torque) does an 11.96, at 135.1 mph, all in first gear, of course. It doesn't pull any harder, but it sure as hell pulls longer :-). It's also making *900* hp, at 15,000 rpm.

Of course, folks who are knowledgeable about drag racing are now openly snickering, because they've read the preceeding paragraph, and it occurs to them that any self respecting car that can get to 135 mph in a quarter mile will just naturally be doing this in less than ten seconds. Of course that's true, but I remind these same folks that any self-respecting engine that propels a Vette into the nines is also making a whole bunch more than 340 foot pounds of torque.

That does bring up another point, though. Essentially, a more "real" Corvette running 135 mph in a quarter mile (maybe a mega big block) might be making 700-800 foot pounds of torque, and thus it would pull a whole bunch harder than my paper tiger would. It would need slicks and other modifications in order to turn that torque into forward motion, but it would also get from here to way over there a bunch quicker.

On the other hand, as long as we're making quarter mile passes with fantasy engines, if we put a 10.35:1 final-drive gear (3.45 is stock) in our fantasy LT1, with slicks and other chassis mods, we'd be in the nines just as easily as the big block would, and thus save face :-). The mechanical advantage of such a nonsensical rear gear would allow our combination to pull just as hard as the big block, plus we'd get to do all that gear banging and such that real racers do, and finish in fourth gear, as God intends. :-)

The only modification to the preceeding paragraph would be the polar moments of inertia (flywheel effect) argument brought about by such a stiff rear gear, and that argument is outside of the scope of this already massive document. Another time, maybe, if you can stand it :-).

At The Bonneville Salt Flats
Looking at top speed, horsepower wins again, in the sense that making more torque at high rpm means you can use a stiffer gear for any given car speed, and thus have more effective torque *at the drive wheels*.
Finally, operating at the power peak means you are doing the absolute best you can at any given car speed, measuring torque at the drive wheels. I know I said that acceleration follows the torque curve in any given gear, but if you factor in gearing vs car speed, the power peak is *it*. An example, yet again, of the LT1 Vette will illustrate this. If you take it up to its torque peak (3600 rpm) in a gear, it will generate some level of torque (340 foot pounds times whatever overall gearing) at the drive wheels, which is the best it will do in that gear (meaning, that's where it is pulling hardest in that gear).

However, if you re-gear the car so it is operating at the power peak (5000 rpm) *at the same car speed*, it will deliver more torque to the drive wheels, because you'll need to gear it up by nearly 39% (5000/3600), while engine torque has only dropped by a little over 7% (315/340). You'll net a 29% gain in drive wheel torque at the power peak vs the torque peak, at a given car speed.

Any other rpm (other than the power peak) at a given car speed will net you a lower torque value at the drive wheels. This would be true of any car on the planet, so, theoretical "best" top speed will always occur when a given vehicle is operating at its power peak.

"Modernizing" The 18th Century
OK. For the final-final point (Really. I Promise.), what if we ditched that water wheel, and bolted an LT1 in its place? Now, no LT1 is going to be making over 2600 foot pounds of torque (except possibly for a single, glorious instant, running on nitromethane), but, assuming we needed 12 rpm for an input to the mill, we could run the LT1 at 5000 rpm (where it's making 315 foot pounds of torque), and gear it down to a 12 rpm output. Result? We'd have over *131,000* foot pounds of torque to play with. We could probably twist the whole flour mill around the input shaft, if we needed to :-).

The Only Thing You Really Need to Know
Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :-)

[edited equations for readability]

Fëakhelek

Nuff said. Although there are still people that think the earth is flat and the space photos are faked. . .

ZoomZoom

As usual another well thought out easy to understand explanation by Buger.

However I suggest that this thread be moved to "The Tech Garage".

cueball

Great write up buger. That made things cristal clear to me. Before I was a little unsure about that subject due to the amount of differents things being said about it. Thanks for clearing everything up.

globi

Somehow I got somewhat involved in another forum regarding that always repeating Power & Torque topic.
Anyway I believe you could explain this much shorter:Also, I started to wonder why some people get so confused about this and thought this could be an explanation:Actually others might have come up with similar conclusions in other threads, but I didn't have the patience to read them and I didn't really see any short and precise ones.

RXhusker

Great to see one of Buger's posts revived :D

Back in ancient times Buger made posts of legend .. long before we even had our cars -- just pre-order emails and lots of dreams ...

kaiser soze

Bruce Augenstein, the author of the article on torque and power that was copied here, has no qualifications or credentials for writing such an article, and unfortunately his ignorance comes through clearly in his article. I actually studied physics as my minor in an accredited university, and I have a great deal of difficulty with that article. Simply put, it is garbage. Augenstein has been contacted on multiple occasions and given plenty of opportunity to retract his article, but he adamantly refuses. The following article is an effort by a legitimate author to mitigate the damage done by Augenstein.

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Plato and Socrates Discuss Torque, Power and Acceleration (Revised 4/30/2006)
- Thomas Barber

Plato: Dude, nice toga. Say, have you heard the news? Torque rules!

Socrates: Torque rules? What in the name of Zeus is that supposed to mean?

Plato: I’m not sure exactly, but it has a nice ring to it. I read it in an article that I found on the Internet. Torque is a “twisting force”, right?

Socrates: Torque is the measurable quantity that translates between straight-line force and rotational motion. To get the torque, you multiply the force by the “effective lever arm”, which is measured along a line that is square to the line of force. In familiar situations such as when you use a wrench to get leverage against a bolt or nut, as long as you apply the force squarely against the wrench handle, the effective lever arm is simply the distance between the center of the bolt and the point where you apply the force.

Plato: The fact that the force that I sense when I tighten my wagon wheel decreases in proportion to the length of the lever arm, tells me that the product of the force and the lever arm doesn’t change. The torque must therefore depend only on the amount of friction in the threads. Speaking of friction, I know that it takes work to overcome friction, so there must be a connection between torque and work.

Socrates: The work associated with any force acting on a moving object is found by multiplying the distance that the object has moved, by the part of that force that is directed in the same direction as the direction of motion. Another essential fact about work is that energy is work waiting to be performed. The work that you perform when you raise a bucket of water from a well, for example, increases the potential energy of the bucket, and you can use that potential energy to perform useful work. The work performed is equal to the weight of the bucket multiplied by the distance that you raise it, and is likewise determined by the torque that you apply to the crank multiplied by the amount of crank rotation needed to raise the bucket.

Plato: So, the work performed is the same as the energy expended, and they depend on force and distance. But how do I account for the effect of how quickly I raise the bucket?

Socrates: Power is the measure of how quickly you are performing work, and because of the equivalence between work and energy, power is also the rate at which energy is being expended or converted from one form to another form. As long as force is measured in the same direction as the velocity, power is equal to the force multiplied by the velocity. Power is also equal to torque multiplied by rotational speed. When you have torque in lb-ft and angular speed in rpm, you simply multiply them together and divide by 5252, to get power in horsepower.

Plato: Where do you get the 5252?

Socrates: One horsepower is equal to 33,000 foot-pounds of work per minute, but first you have to convert torque and angular speed to force and linear speed. When you turn the crank of the well, the distance that the bucket will move in one full rotation will be the same as the circumference of the spool, which is equal to the radius multiplied by twice pi, about 6.283. To cut to the chase, 33,000 divided by 6.283 is about 5252.

Plato: So, at 5252 rpm, torque and power are the same, right?

Socrates: No, because they don’t measure the same thing, and because the value 5252 is merely an artifact of the units of measure, and they are arbitrary. In most of the world, torque is expressed in Newton-meters (Nm), and power is expressed in Watts or kilowatts (kW), which we use for electrical power. The engine speed where torque in lb-ft and power in hp have the same numerical value happens to fall within the operating range of most engines, so it is convenient to use a single numerical scale for both torque in lb-ft and power in hp on dynamometer plots. When that is done, the two curves cross at 5252 rpm, but if other units of measure are used, the two curves might not even cross.

Plato: Well, everyone knows that torque is what causes acceleration, so I don’t get why power matters.

Socrates: There isn’t any consistent, objective basis for attributing causality of acceleration to either torque or power exclusive of the other. Torque and power each have a specific quantitative relationship to acceleration, and that is all that is actually meaningful to us. At any given instant in time, acceleration is equal to actual power, divided by mass and by the vehicle speed. Acceleration also has a simple relationship to wheel torque, but the proportionality between acceleration and engine torque depends on the gear ratio, which can be easily altered at almost any time.

Plato: That article that I read on the Internet, said that power is just an esoteric measurement of sorts. The author said that the only way that anyone on the planet measures power is by measuring torque and then calculating power from torque.

Socrates: It is not true that it is necessary to first measure torque in order to measure power, but if that were true, the compelling question would be why that would be thought relevant, especially since you must also measure the engine speed in order to derive power from engine torque. With inertial dynamometers, the rotational speed of the drum is repeatedly measured in order to determine its angular acceleration, and power is then determined from the acceleration and from the drum’s inertial moment. Brake dynamometers, on the other hand, vary the load so that the speed can be stabilized along short steps where the measurements are taken, in order to prevent the engine’s own inertial moment from influencing the results. If you were to apply the engine to the task of lifting a tank of water against the force of gravity and you had a way to quickly vary and control the amount of water in the tank, you would have in effect a brake dynamometer. Multiply the speed of the tank by its weight, and you have the power.

Plato: That article also talked a lot about how, in a given gear, acceleration tracks with the engine torque. The author said that since the relationship between power and acceleration isn’t consistent, power isn’t meaningful from a driver’s perspective, and torque is the only thing that the driver feels.

Socrates: It makes absolutely no sense to infer, from the fact that acceleration in a given gear tracks with engine torque, that torque is what the driver feels. Acceleration is what the driver feels, and the pertinent question is whether the acceleration at a given instant in time depends on more than just the engine torque. Engine torque effectively tells you how much fuel energy is converted to kinetic energy during each single rotation of the crank, and in order to know the rate at which the vehicular kinetic energy is increasing, you have to multiply by the engine speed. Power is the precise measure of how quickly the potential energy trapped in the fuel is being converted into vehicular kinetic energy, and the more quickly that energy conversion is taking place, the greater the acceleration.

Plato: But if acceleration is proportional to power, why doesn’t acceleration track with power as the engine speed increases in a given gear?

Socrates: Because the vehicle speed also changes, and for reasons that are related to the fact that kinetic energy depends on the square of the vehicle speed, you don’t get the same acceleration at higher vehicle speed that you do at lower vehicle speed, for the same power. No matter how unintuitive this may seem, the pertinent fact is that at any instant in time, acceleration is proportional to actual power. You can change the relationship between acceleration and engine torque simply by changing the gear ratio, but even though changing the gear ratio will generally change the power, the proportionality between acceleration and power depends only on the mass and the vehicle speed.

Plato: The waterwheel anecdote seemed potentially useful, but the way it was presented left me a little confused. The author prefaced that anecdote by saying that he was going to explain why we care about power. Consequently, I was looking for him to clearly establish the connection between power and acceleration, but I don’t think that he ever did manage to do that. He did calculate the power of the waterwheel, and it was surprisingly small. Perhaps I was supposed to infer a connection between the meager power and the reduced torque at the output after the gearing was applied.

Socrates: He more or less said that the substantial torque of the waterwheel would be greatly reduced if you applied gearing so that its output speed will match the greater rotational speed of truck wheels on the highway. I feel that it is important to shine a particular light on this torque conversion business, in order to give people who only appreciate torque, a better appreciation of power. Except for internal frictional losses, power is the same at both the input and the output of the transmission. As such, if the gearing increases the rotational speed, there must be a compensating decrease in torque, and vice versa. Torque at the output, for a given output speed, depends on the power. Note also that although a change to the diameter of the drive wheel will change the relationship between the longitudinal force and the wheel torque, you can still ascertain the change in acceleration by reading the power curve at the new engine speed.

Plato: I was also a little confused by the example that involved the two corvettes, which have identical engine torque peaks at the same engine speed, and identical gearing, yet differ in peak power. He talked about “pulling longer” vs. “pulling harder”.

Socrates: The only point that I was able to discern in that extended discussion is that the peak acceleration in a given gear coincides with the engine torque peak. This observation is as inconsequential as it is manifest, and it amounts to more obsessing over what happens “in a given gear”. As a necessary consequence of the specific conditions that he stipulated, both cars will exhibit the same peak wheel torque coinciding with their shared engine torque peak. Yet, the vehicle with greater peak power will pull away from the other vehicle before either of them reaches its power peak in 1st gear, and it will remain in the lead from then on. The more important fact to note about this, however, is that if you remove the constraint that the two cars have identical gearing, the car with greater peak power may well exhibit greater peak wheel torque and greater peak acceleration even if its peak engine torque is less than that of the other vehicle.

Plato: Toward the end of the article he said that the power peak is the best engine speed for any given vehicle speed.

Socrates: That was probably the high point of his article, although it seems a curious substitute for a simple acknowledgement of the simple fact that acceleration is proportional to power. He then summarized with that sad business about it being better to make torque at high rpm than at low rpm because you can then take advantage of gearing. What is to be gained by jumping through hoops to avoid a simple acknowledgement of the simple fact that acceleration is proportional to power?

Plato: What about the engine performance characteristics that people associate with enhanced engine torque?

Socrates: Effects such as stronger acceleration from a full stop and less frequent shifting are the result of enhanced engine performance at low and moderate engine speeds. But, I prefer not to equate torque with performance at low engine speed, because that is misleading and contributes to other misunderstandings, including the misunderstandings that lead misguided people to assert that power is meaningless and that engine torque is what causes acceleration. The shape of the engine torque curve reveals the variation in the amount of air drawn into the cylinder on the intake stroke at different engine speeds, which is influenced by a variety of factors such as valve timing, cylinder shape, and the shape of the intake and exhaust manifolds. Piston stroke also influences the shape of the torque curve, because piston stroke is related to factors such as cylinder shape, which have primary influence on the way that engine torque varies with engine speed. Some people believe that the explanation for why longer stroke means greater low-end torque is because of the increased length of the effective lever arm, but this is a fundamental misunderstanding, and there are three good ways to show why this isn’t correct. First, for a given displacement, if you increase the stroke, you decrease the piston surface area at the same time, which nullifies the effect of the increased lever arm, since the force depends on the surface area of the piston face. Second, torque determines the amount of work performed over a given amount of crank rotation, so if the relationship between stroke and torque were that simple, you could get free energy just by making the cylinder long and slender. Third, if the relationship between stroke and torque were that simple, the improvement in torque would not favor any particular part of the operating range. This last problem in particular is so obvious, that in order for anyone to believe that the increased lever arm is the explanation for why low-end torque is related to stroke, they would have to have some truly inexplicable notion about the role of torque at high engine speed. Performance at high engine speed depends on engine torque just the same as performance at low engine speed. If you want to improve the peak power, you design the engine so that volumetric intake and torque will be improved at higher engine speed. When the engine design instead strives to enhance torque at comparatively low engine speed, the meaningful beneficiaries such as strong acceleration from a full stop, are represented equally well by available power at those engine speeds as they are by available torque. All in all, those meaningful performance qualities should be associated with de-emphasis of peak power, and not with torque per se, notwithstanding that there is a strong correlation between low-speed torque and those specific qualities.

Plato: What is your final thought about the “Torque rules!” proclamation?

Socrates: When people say things like “Torque rules!” are they talking about the available torque over a practical range of engine speeds, or about the peak torque? People often quote the peak engine torque as though it is expected to reveal those meaningful performance qualities that benefit when peak power is deemphasized, yet the relationship between the peak torque and the available torque over a practical range of low and moderate engine speed isn’t consistent. The torque peak per se just isn’t important enough to make a fuss over. It makes perfect sense to advocate the advantages of actual performance over a practical range of low and moderate engine speed. But doing that in a way that attributes that sort of performance specifically to torque requires that power be interpreted in the special sense of its peak value while torque is interpreted differently. The proclamation “Torque rules!” is really about emotionalism, and as such, it is not surprising that it doesn’t make much sense.

Plato: I sometimes wonder if part of the reason that many people associate engine torque with low engine speed is due to misapplying the affinity between low rotational speed and torque, which occurs at the output of the transmission, to the engine directly. By the way, did I tell you that I like your new toga?

Socrates: I had my colors done last week, and I think that this new chartreuse will be a big hit at the Dionysus.

Plato: Dude, when was the last time you had those legs waxed?

Skythe

Thanks for the refresher course, I tried making a thread that dissolved the whole irrational love of horsepower but I was foiled...some people just didn't get the message. I hope this opens up peoples eyes and minds to what really matters and how relative horsepower is.

Skythe

Sticky!
Sticky!
Sticky!
Stick!y
Ky Jelly!!
Sticky!
Sticky!
Sticky!

W1CK3Dninja

i can explain horsepower and torque about the rx8.........it has none.

Razz1

So if the first thing you look at it torque, then why in the Hell did big Daddy Rat Fink pick the RX8 to buy?

yiksing

"It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing"

Can someone explain this to me, I never quite grasp this part even after reading numerous times?