Torque Explained

[neoviper]

This thread is calling for the attention of all Moderators, Wiseman, and any other knowledgeable members on this site.

The first thing you usually hear any newb say is " How can I make more power? ", " How much HP will I gain from xxx?", and plenty other questions related to HP. Most people (not all) draw all the attention to HP in dyno runs and don't pay much attention to the second number on that slip.

I for one am interestred in learning more about tourqe, how it's measure, how it's produced, proven methods as well as theories on increasing it.

This forum doesn't really have any threads that get into this, or explain it too well. I am hoping that this thread and all the input that goes into it will educate others such as myself in better understanding torque.

Have at it boys!

 

[dsm-onster]

There is no profit in arguing math.
"HORSEPOWER: In its purest definition is: 1 HP= 33,000 Foot-Pounds of WORK Per Minute. In measurement, it is TORQUE multiplied by RPM divided by 5252."

Please see JIM MILLER for more details and the literal definition of torque.

I could try to simplify horsepower and torque for just the DSM community but there is already an open thread for misleading statements.

This is right. Work = horsepower. Work, W = Fd, is an exchange of force for a given distance displaced. This is horsepower. We exert a maximum ft-lbs of torque on our head studs, but at the end of the staging the stud does not move; there is no distance displaced. Thus, no work is done at the point the stud resists the torque 100%. Torque on the dyno graph, though charted vs. rpm does not indicate how much work is being done by itself. It is the torque over time that determines how a car accelerates down the track. Thus we can calculate hp without knowing torque by simply determining your speed at the end of the track from a zero start.

Simply deriving the formula for Kinetic Energy, we can see this:

W = Fd .........F = ma
W = mad
W = m(v/t)(v/2)t
W = 1/2mv^2

d is distance displaced. d is not the moment arm for torque. Torque does not accelerate your car down the track, just like it does not move the head stud nut. Another rendering of hp is 1hp of work = 550ft-lbs per second. 550 ft lbs used in 1 second of time gets you down the track real slow. You'll coast and stop because after 1 second of 550 ft-lbs of torque you then have none. But this is more torque than a z06 delivers at peak! So it can be said in two ways:

1. It's the use of torque, or HP, that generates and determines acceleration.
2. You have to have that torque used over time to maintain acceleration.

Our cars have ZERO wheel horsepower when parked.

CTP, A gallon of water may or may not weigh 8.33 lbs . If all we looked at were torque on the dyno, then we would all migrate to diesel platforms to win at the track. It's true that you cannot have one without the other but that does not mean they "measure the same thing".

hp = torque * RPM / 5252. That IS it. "Horsepower is a number calculated from Torque and RPM." AND yes, "It's a measure of work. In the case of a car it's a measure of acceleration." You said slowgsr is "wrong" when you said just what he said:

torque* RPM / 5252 = "a measure of work"

500 ft-lbs of torque at 4000rpms = 381hp. 250ft-lbs at 8000rpms = 381 hp. Same work gets done.

I'll quote your link for those wanting to understand what's important to accelerate a car the most (which also goes along with the above math I've pointed out):

"Engine Torque is about as useless an attribute of a bike as can be. Two equal weight bikes, both make a maximum of 70 ft lbs of torque, which one accelerates faster? Why, the one with the most Horsepower! 70 ft lbs of torque at 5,000 rpms can't beat 70 ft lbs of torque at 10,000 rpms! Why? Because torque times rpms equals horsepower and it is horsepower that moves your bike down the road. You can gear a 10,000 rpm engine twice as low as a 5,000 rpm engine thus doubling the Rear Wheel Torque and therefor the force at the tire contact patch."

. . . ."Engine Horsepower is a measure of the engines ability to do work per unit time and work per time is the moving of a weight some distance in a given amount of time."​

Or going 1320 feet in a certain elapsed time.

Broadening your hp curve will give you a better 1/4 mile time. It will also raise your torque if you don't increase you rev limit. To me, it is a personal preference to tune using the torque curve or tune using the hp curve, because I agree with you: both "HP and torque are two different ways to measure the same thing". You can't increase your hp at a certain rpm without increasing your torque at that given rpm. So while tuning, you can shoot for highest torque at that rpm or highest hp at that rpm, and you'll achieve the same results. You're not really wrong. Just your words are . I see you understand how this works (not that my opinion conts fo very much), but the explination is just not correct. Slowgsr said just what you're saying.

Meaning, if you're going 60 mph, you'll want to be in the gear which lands closest to the peak hp for maximum acceleration.

Good job, Peeps .

Matt hit the nail on the head for starting down the path to creating a hp curve that suites your goals. Acceleration is directly related to HP not torque. Work or HP = mass X accelertion X distance. . . Regardless of the torque. Look at the end of the first paragraph I quoted from that website CTP graciously provided. Th old sayying, "torque wins races" is misleading. Higher torque at the wheels over a longer period of time wins races.



I believe Slowgsr's allusion to 5252rpms being related to VE comes from the fact that VE is directly proportional to torque. . . ???

The VE curve looks like the torque curve. I know that much. . .

 

[TunaTalon]

Matt,
That was a lot of words. But all accurate. Now that we have settled what torque is, it looks like dsm-onster is the man to explain why the "curve" is important in tuning. I think that dsm-onster is trying to say that two tunes both peaking at 381 hp can have different performance? How could that be if the peak horsepower is the same for both curves?

Why does the performance world have no word for the concept of "horsepower under the curve"? What would be a good name for that concept? How about "average horsepower to the top of second"? Yeah, that's too long. Where would the low RPM on the curve be, or the highest RPM of interest? Maybe the two shift points that pass through 60MPH?

Could there even be a single measure that indicates performance over a RPM range.

 

[dsm-onster]

It's hard to explain without just vomitting formula .

To illustrate power under the curve, two hypothetical dsms with same gear set, different peak hp, different tune:

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Which has the most area? grey + green, or purple + green.

Having more average work done for longer means better ET. ETs win races. Not trap speeds. Average work is the sum of the instantanious hp (all the hp numbers at particular rpm points between the shift points) along the curve divided by the intervals of measure (the rpm difference between the shifts). This is basic calculus babble. Not condescending. It's just stuff science majors are reqired to know. And doesn't supercede real world proof. The integration of the hp curve between the shift points gives the area.

There's no word because I think it's a conspiracy . I guess we can call it RPM-HP. It doesn't matter who revs to what, the area (length times width, x times y, rpm times hp) will show who's best between the shift points.

 

[TunaTalon]

It's hard to explain without just vomitting formula .


Having more average work done for longer means better ET. ETs win races. Not trap speeds. Average work is the sum of the instantanious hp (all the hp numbers at particular rpm points between the shift points) along the curve divided by the intervals of measure (the rpm difference between the shifts). This is calculus babble. The integration of the hp curve between the shift points gives the area.

There's no word because I think it's a conspiracy . I guess we can call it RPM-HP. It doesn't matter who revs to what, the area (length times width, x times y, rpm times hp) will show who's best between the shift points.

After posting I found this site giving the calculations for average HP and torque.
Impulse Engines : Performance : More Average Torque At least someone is thinking about it but personally I don't care about where the hp curve goes after it's time to shift anyway. (7000 for my Talon) and with a high stall torque converter the Talon doesn't spend much time at 1000 RPM.

For what it's worth my stroker project was designed for the red line:
Longer stroke moves the torque peak down.
264/264 cams raises torque at low/mid range.
8.8:1 pistons for more off boost torque.
EVO3 16G spends less time off boost.
High stall torque converter spends little time at low RPM.

My butt dyno says it all works but the AWD dyno says I have a low horsepower.

You're probably right about the conspiracy. After all of my plotting and planning I don't have a big number for bragging rights.

 

[dsm-onster]

I would have just gotten a set of 272s and mucked with the cam timing abit. 272s make power at 5.8K with a stroker like they make power at 7k with a stock stroke. It's all about air velocity . . . But otherwise, it looks to be a FAT power band. I bet it's fun, even for an automatic. I think DSM autos are very underrated, BTW.

Have you hit the track?

 

[CTP]

CTP, A gallon of water may or may not weigh 8.33 lbs . If all we looked at were torque on the dyno, then we would all migrate to diesel platforms to win at the track. It's true that you cannot have one without the other but that does not mean they "measure the same thing".

It's all the same when put on a dyno chart. Having both just makes things easy for you because a torque curve is easier to look at when tuning and a HP curve is easier to look at when figuring out how fast the car is going to go.

Broadening your hp curve will give you a better 1/4 mile time. It will also raise your torque if you don't increase you rev limit. To me, it is a personal preference to tune using the torque curve or tune using the hp curve, because I agree with you: both "HP and torque are two different ways to measure the same thing". You can't increase your hp at a certain rpm without increasing your torque at that given rpm. So while tuning, you can shoot for highest torque at that rpm or highest hp at that rpm, and you'll achieve the same results. You're not really wrong. Just your words are . I see you understand how this works (not that my opinion conts fo very much), but the explination is just not correct. Slowgsr said just what you're saying.

I think you missed my point. The torque curve is what people (at least the smart ones) look at while tuning because it's the best snap shot of what the motor is doing at any given RPM due to the fact that it isn't effected by RPM. A sag in engine output at 3,000 RPM isn't going to be very noticable on the HP curve because it occurs before the crossover point and therefore is understated on that curve. The opposite is true at higher RPM when very small changes in torque result in large changes in HP. Looking at the torque curve, it doesn't matter what RPM you're at, everything is the same. A drop of 10ft/lbs at 4,000rpm is the same loss of engine output as a drop of 10ft/lbs at 8,000rpm and both can be delt with accordingly. Granted, if you're on top of things you can just take the multiplier into account and look at the HP curve anyway, but who does that? It's just unnecessary work.

Once again, if you know how they relate, they're just two different ways of looking at the same thing. One is more convenient for some purposes and the other is more convenient for other purposes. In the end they show the same thing (engine output), just in different ways.

 

[dsm-onster]

. . .A sag in engine output at 3,000 RPM isn't going to be very noticable on the HP curve because it occurs before the crossover point and therefore is understated on that curve.

. . .One is more convenient for some purposes and the other is more convenient for other purposes. In the end they show the same thing (engine output), just in different ways.

This is a very good point. I see what you're saying. Thanx for explaining in the first place. Instead of just telling these guys they're wrong.

 

[TunaTalon]

Earlier in this thread I said that "there is no profit in arguing math". Ah yes, but arguing about how data is presented has served me well.

In post 28 dsm-onster presented a chart to show clearly and easily that a wider torque curve will work better in the real world than a higher, but narrow peak. If he had posted a piece of a spread sheet showing the same data as a long list of numbers no one would have understood. (well maybe CTP)

In post 31 CTP said:

"A sag in engine output at 3,000 RPM isn't going to be very noticable on the HP curve because it occurs before the crossover point and therefore is understated on that curve. The opposite is true at higher RPM when very small changes in torque result in large changes in HP."

Notice that CTP's not saying that the data is different, or that the calculation changes, just that the way the data is plotted affects how it is visualized.

I love it when the math works out the same as the real world experience that it describes. But the Horsepower/torque curves from an AWD dyno is not even close to my real world experience with my stroker Talon. With a manual transmission there is a hard link from RPM, to Speed, to Time and the chart pretty much matches experience. However, I don't have RPM in my seat-of-the-pants axis. I pretty much experience acceleration as force on my er back (what did you think I was going to say?) over time.

With a high stall torque converter there is only a casual link between RPM and speed. On the dyno sheet of my Talon the range from 1K RPM to 4K RPM is the same size as from 4K to 7K. In the real world that first 3K comes on almost as fast as the throttle goes down but the second 3K takes some few seconds. With RPM as the X axis my Talon looks like it will barely get out of it's own way at low RPM. If the same data were plotted with seconds on the X axis it would match my seat-of-the-pants dyno.

The math may never change but how we present horsepower and torque will affect the way we think about tuning.

If you are still reading you may enjoy: http://www.precisionautoresearch.com/Race Intelligence Booklet\Racing Intelligence.pdf