[XutvJet]

At this point, I'm not sure what you are debating. Force, power, potato, patoto. It's all the same. Twist results into forward momentum. HP is derived from torque and is a measure to do work over time. That's what most people only need to understand.

A turbo motor that generates 400wtq from 1500rpms to 5000rpms and 400whp at 6500rpm is going to be stronger accelerating than a naturally aspirated motor making 400wtq from 3000 to 5000rpms and 450whp at 7000rpms. There is simply more power under the curve with the turbo motor.

I completely understand what torque is and it's relationship to HP. I also fully understand the importance of ideal shift points and how to calculate them as I was an avid drag racer years ago and have well over 500 1/4 mile passes under my belt with a handful of cars. I lived this stuff and want to know what works for all my cars. 1000 ft/lbs of torque doesn't necessarily make for a fast car. If all out torque was the answer, we'd all have turbo diesels.

[albertw]

Originally Posted by XutvJet

At this point, I'm not sure what you are debating.

I don't see a debate here. dradernh somewhat indirectly asked a question and I started the ball rolling with a brief answer. A number of other people added more information, and some of them included statements that are objectively wrong. A few people tried gently to correct those errors, to make things less confusing for anyone thinking about these issues for the first time.

If someone convinced me that one of my statements was incorrect, I would be grateful for having my knowledge base improved rather than whiny.

This is nothing like the debate over whether an LSD increases or decreases the fun of driving our cars. That's a matter of opinion. The question of how to determine optimum shift points is a matter of getting the facts and the physics correct. It is true that long experience can give you useful rules of thumb, but truly understanding the issues is more satisfying. (Now, that's an opinion you can debate if you wish.)

[albertw]

Originally Posted by aerobod

Torque is dimensionally equivalent to energy (Nm are equivalent to J in the SI system)

There might be some deeper meaning here, but to me it is just a coincidence. Torque and energy are different concepts that happen to have the same units. At one time there was a push to call one foot pounds and the other pound feet, to emphasize the difference. I'm not sure where that went.

[aerobod]

Originally Posted by albertw

There might be some deeper meaning here, but to me it is just a coincidence. Torque and energy are different concepts that happen to have the same units. At one time there was a push to call one foot pounds and the other pound feet, to emphasize the difference. I'm not sure where that went.

Torque is directly related to angular measurement of work done, which is defined in the SI system as applying a force of one Newton over a distance of one metre. In the case of a torque, this displacement is per radian, which is a circumferential distance of one metre when the radius arm is one metre. Work done is due to energy expended, measured in Joules - one Joule is one Nm. One revolution is 2π (pi) metres at a radius of one metre, so a torque of 1Nm applied for one revolution is 2π J, or 6.283J.

So the relationship is not coincidental, it is at the heart of the definition of angular and linear work/energy, which is directly related to power as the rate of energy / work per second in Watts.

In terms of engines, a torque of 500Nm (369 lbft) at 300 radians per second (2,865 RPM) produces 150,000 Watts (201 BHP), or 400Nm at 600 radians per second (5,760 RPM) produces 240,000 Watts (322 BHP). Much easier to relate torque and power in SI units than in imperial units!

[albertw]

Originally Posted by aerobod

Torque is directly related to angular measurement of work done, which is defined in the SI system as applying a force of one Newton over a distance of one metre. In the case of a torque, this displacement is per radian, which is a circumferential distance of one metre when the radius arm is one metre. Work done is due to energy expended, measured in Joules - one Joule is one Nm. One revolution is 2π (pi) metres at a radius of one metre, so a torque of 1Nm applied for one revolution is 2π J, or 6.283J.

So the relationship is not coincidental, it is at the heart of the definition of angular and linear work/energy, which is directly related to power as the rate of energy / work per second in Watts.

OK, coincidence it not the right word. Perhaps it is better to describe it as the result of a mathematical convenience.

It is convenient to redefine force in a rotating system as torque - the tangential component of a force times the distance between the point at which the force acts and the axis of rotation. As a result of this definition, when dimensionless radians are used to quantify the amount of rotation the distance over which the force has acted falls out of the multiplication of the number of radians times the torque (because each radian of rotation means the force has acted along an arc length equal to the radius of the system). Thus work (the amount of energy transferred from the agent applying the force to the object being moved) equals force times distance in both rotating and linear motion.

Clearly you understand this. When you pointed out that torque and energy have the same units, I wanted to make it clear that that does not mean they are the same thing, because this was confusing to me when I first started thinking about these issues.

Torque is a convenient way of describing the twisting force that a wrench applies to a nut or a connecting rod applies to a crankshaft, but no energy is transferred until the nut or crank turns. The amount of energy transferred still boils down to force times the distance over which the force acts, just expressed in terms that are more convenient to use.

[aerobod]

Originally Posted by albertw

OK, coincidence it not the right word. Perhaps it is better to describe it as the result of a mathematical convenience.

It is convenient to redefine force in a rotating system as torque - the tangential component of a force times the distance between the point at which the force acts and the axis of rotation. As a result of this definition, when dimensionless radians are used to quantify the amount of rotation the distance over which the force has acted falls out of the multiplication of the number of radians times the torque (because each radian of rotation means the force has acted along an arc length equal to the radius of the system). Thus work (the amount of energy transferred from the agent applying the force to the object being moved) equals force times distance in both rotating and linear motion.

Clearly you understand this. When you pointed out that torque and energy have the same units, I wanted to make it clear that that does not mean they are the same thing, because this was confusing to me when I first started thinking about these issues.

Torque is a convenient way of describing the twisting force that a wrench applies to a nut or a connecting rod applies to a crankshaft, but no energy is transferred until the nut or crank turns. The amount of energy transferred is still boils down to force times the distance over which the force acts, just expressed in terms that are more convenient to use.

I see what you mean, what you are talking about is the difference between static and dynamic torque - static torque is where no work is done such as when a wrench is used to reach a final torque value, dynamic torque is when work is done such as through the rotation of a crankshaft that is used to accelerate an engine.

With a static torque there is an equal and opposite resistive torque that prevents work being done, analogous to a force being applied to a static object in a straight line before friction is overcome. It is really the expression of static force at a reference distance in Nm at zero radians that can be confusing, as dynamic torque is still measured in the same units, Newton metre radians, but with radians being dimensionless, only Nm is expressed in the units of measure.

[albertw]

Originally Posted by aerobod

I see what you mean, what you are talking about is the difference between static and dynamic torque - static torque is where no work is done such as when a wrench is used to reach a final torque value, dynamic torque is when work is done such as through the rotation of a crankshaft that is used to accelerate an engine.

With a static torque there is an equal and opposite resistive torque that prevents work being done, analogous to a force being applied to a static object in a straight line before friction is overcome. It is really the expression of static force at a reference distance in Nm at zero radians that can be confusing, as dynamic torque is still measured in the same units, Newton metre radians, but with radians being dimensionless, only Nm is expressed in the units of measure.

Thanks for the reassurance, aerobod. (I'm largely self-taught on these issues, starting from the basic equations of motion in my Physics 101 textbook from 50 years ago.)

I've never used the term dynamic torque, but a quick google search indicates to me that it is conceptually similar to static torque, except that the torque is applied to a body that is already rotating. An additional complication is that the torque at the crankshaft varies substantially as the pistons move up and down, so the torque measured there is typically an average value of the torque over many engine revolutions. By the time the torque gets to the tires the fluctuations are largely damped out, so the torque at the rear wheels is essentially identical to static torque. (For example, to calculate the force the tires exert on the road you treat it as if it was a static torque.) Conceptually, to me it bears no resemblance to energy.

Is this right? Wrong? Incomplete?

[XutvJet]

It's getting really nerdy in here.....

[aerobod]

Originally Posted by albertw

Thanks for the reassurance, aerobod. (I'm largely self-taught on these issues, starting from the basic equations of motion in my Physics 101 textbook from 50 years ago.)

I've never used the term dynamic torque, but a quick google search indicates to me that it is conceptually similar to static torque, except that the torque is applied to a body that is already rotating. An additional complication is that the torque at the crankshaft varies substantially as the pistons move up and down, so the torque measured there is typically an average value of the torque over many engine revolutions. By the time the torque gets to the tires the fluctuations are largely damped out, so the torque at the rear wheels is essentially identical to static torque. (For example, to calculate the force the tires exert on the road you treat it as if it was a static torque.) Conceptually, to me it bears no resemblance to energy.

Is this right? Wrong? Incomplete?

Much is correct, but the way to look at static torque vs dynamic torque is that static torque is just a specific case of dynamic torque where no work is done, but instead all shear stress applied is instead resisted by an equivalent shear strain.

If you think of tightening a bolt, initially a low torque is applied as the two surfaces being bolted together are not touching. As the bolt rotates work is done (expressed as Newton metre radians, i.e. energy in Joules). Initially all torque is used to overcome the thread friction (shear stress due to friction causes shear strain in the bolt) but then as the bolt starts clamping, strain is induced longitudinally in the bolt due to the increasing stress applied as the bolt clamps tighter. When the torque applied is 100% used to induce longitudinal strain in the bolt there is no longer dynamic torque, only static torque.

Another example is if you can think of a rope wrapped around a very long shaft which is supported by a bearing near each end and has a propellor on one end. Initially when the rope is pulled with a continuous linear force, the shaft will accelerate until the propellor reaches a stable speed due to the work it is doing to thrust air. If the propellor was hypothetically 100% efficient at creating thrust and there was no friction in the bearings, the energy in the airflow would equal the energy transferred via the shaft torque would equal the linear energy imparted by pulling on the string. The propellor is effectively converting shaft torque to rotational and longitudinal lift and drag on each blade.

In the above example, you could replace the linear rope drive for energy input with an electric motor that just applies energy directly as a dynamic torque.

[albertw]

Originally Posted by aerobod

static torque is just a specific case of dynamic torque where no work is done

Thanks again, aerobod. That statement is enough to assure me that my google search of dynamic torque gave the right answer.

[aerobod]

Originally Posted by albertw

Thanks again, aerobod. That statement is enough to assure me that my google search of dynamic torque gave the right answer.

Yes, clarifying though, a rotating engine is producing dynamic torque at the crankshaft and at the wheels when they are rotating, so work is being done and torque is equivalent to energy transferred. A bolt that is not rotating when a torque is applied is experiencing static torque.

[albertw]

Originally Posted by aerobod

Yes, clarifying though, a rotating engine is producing dynamic torque at the crankshaft and at the wheels when they are rotating, so work is being done and torque is equivalent to energy transferred. A bolt that is not rotating when a torque is applied is experiencing static torque.

Now it's my turn to quibble. It's not the amount of energy transferred until it is multiplied by the number of radians of rotation. You know this since you said it in an earlier post, so I think the issue is the wording, not the underlying understanding. Torque alone is not equivalent to energy transferred, based on what I understand equivalent to mean.

(To me, equivalent means basically the same, with maybe a constant needed to change one thing into the other. I suppose the number of radians of revolution might be considered a sort of constant if every comparison of energy transferred in this context uses the same number of radians. But if that's what you mean, then I'd say this is a good example of something made unnecessarily complicated to make it harder for non-experts to understand.)

[aerobod]

Originally Posted by albertw

Now it's my turn to quibble. It's not the amount of energy transferred until it is multiplied by the number of radians of rotation. You know this since you said it in an earlier post, so I think the issue is the wording, not the underlying understanding. Torque alone is not equivalent to energy transferred, based on what I understand equivalent to mean.

(To me, equivalent means basically the same, with maybe a constant needed to change one thing into the other. I suppose the number of radians of revolution might be considered a sort of constant if every comparison of energy transferred in this context uses the same number of radians. But if that's what you mean, then I'd say this is a good example of something a certain amountmade unnecessarily complicated to make it harder for non-experts to understand.)

OK, maybe this is where the misunderstanding is. ‘Equivalent to’ in my mind is not the same as ‘equal to’.

The thing is dynamic torque requires angular velocity to be present, if angular velocity is zero, then you have a static torque. This means that a certain non-zero number of radians of rotation has to take place. The dynamic torque value per radian in Newton metres is equivalent to the energy value in Joules. The torque is not the energy or work done, but the torque value is equivalent to the work done / energy.

Perhaps I did add confusion in trying to strive for accuracy, as the dynamic torque measured on an engine has no meaning without angular rotation.

It is easy to look at energy transfer, force / thrust at the wheels, etc, working with Joules transferred when it is directly related to the torque and additionally, easily related to power when the angular rate in radians per second is multiplied by dynamic torque in Newton metres.

[albertw]

[QUOTE=aerobod;25139086]OK, maybe this is where the misunderstanding is. ‘Equivalent to’ in my mind is not the same as ‘equal to’.

The thing is dynamic torque requires angular acceleration to be present, if angular acceleration is zero, then you have a static torque. This means that a certain non-zero number of radians of rotation has to take place. The dynamic torque value per radian in Newton metres is equivalent to the energy value in Joules. The torque is not the energy or work done, but the torque value is equivalent to the work done / energy.

QUOTE]

We should probably take this to private messages. I'm pretty sure we agree on the reality of what happens since I agree with everything you say about what actually happens. Then you get to the conclusion and it makes no sense to me. Perhaps the easiest way to illustrate that is to point out that a logical consequence of your statements is that when a car is travelling at a steady speed (static torque by your definition) there can be no energy transferred from the engine to the environment because there is no angular acceleration. That follows directly from your earlier statement that "static torque is just a specific case of dynamic torque where no work is done".

I'd love to have a vehicle that expends no energy when at a steady speed.

[aerobod]

Originally Posted by albertw

[I'm pretty sure we agree on the reality of what happens since I agree with everything you say about what actually happens. Then you get to the conclusion and it makes no sense to me. Perhaps the easiest way to illustrate that is to point out that a logical consequence of your statements is that when a car is travelling at a steady speed (static torque by your definition) there can be no energy transferred from the engine to the environment because there is no angular acceleration. That follows directly from your earlier statement that "static torque is just a specific case of dynamic torque where no work is done".

I'd love to have a vehicle that expends no energy when at a steady speed.

Static torque is when there is no movement, not steady state movement. Any movement or acceleration of a vehicle from the engine will be due to dynamic torque produced by the engine. Unfortunately for some reason I wrote ‘angular acceleration’ when I meant ‘angular velocity’, otherwise everything else is correct. Bit tired tonight while time shifted a couple of time zones.

[albertw]

Originally Posted by aerobod

Static torque is when there is no movement, not steady state movement. Any movement or acceleration of a vehicle from the engine will be due to dynamic torque produced by the engine. Unfortunately for some reason I wrote ‘angular acceleration’ when I meant ‘angular velocity’, otherwise everything else is correct. Bit tired tonight while time shifted a couple of time zones.

That clears that up!

I think we agree on all aspects of this issue except your use of the word equivalent. You may think it adds information, but I think that in the context of offering assistance to someone trying to figure out the meaning of torque and horsepower curves, saying torque is equivalent to energy just adds confusion. Briefly (I'm not implying you don't understand this), here is the difference.

Conceptually, torque is a force applied at a distance from the rotational axis of an object. That's what it is whether it's static or dynamic torque.

Conceptually, energy in this context is what is transferred when a force is applied to an object and that object moves a distance as a result of the force. It's the same whether the motion is in a straight line or along the circumference of a circle.

To me the difference is so stark that I have trouble imagining why you would want to call them equivalent.

In a broader context, energy is an abstract concept that is so fundamental to all of physics that it is silly and somewhat offensive to say that it is equivalent to something that is not energy.

[babaikram]

It is a thread like this that makes me love 2addicts forum. Knowledge and passion roll into one makes for a good discussion. i have learnt a bit so far. Keep it going

[aerobod]

Originally Posted by albertw

That clears that up!

I think we agree on all aspects of this issue except your use of the word equivalent. You may think it adds information, but I think that in the context of offering assistance to someone trying to figure out the meaning of torque and horsepower curves, saying torque is equivalent to energy just adds confusion. Briefly (I'm not implying you don't understand this), here is the difference.

Conceptually, torque is a force applied at a distance from the rotational axis of an object. That's what it is whether it's static or dynamic torque.

Conceptually, energy in this context is what is transferred when a force is applied to an object and that object moves a distance as a result of the force. It's the same whether the motion is in a straight line or along the circumference of a circle.

To me the difference is so stark that I have trouble imagining why you would want to call them equivalent.

In a broader context, energy is an abstract concept that is so fundamental to all of physics that it is silly and somewhat offensive to say that it is equivalent to something that is not energy.

The thing is for us pedants (and you have to admit that we both fall into that category) is that equivalent and equal are not the same thing. When talking about the equivalent values as has been the case in relating Nm values of dynamic torque when an angular displacement happens and energy in Joules, there is equivalence in values. No mention or intention to imply torque=energy.

Returning to the beginning and the point of the thread was shift points and what happens from a torque perspective when moving from 4 to 5 and the relationship between torque and power and how it is easy to calculate torque and power in SI units due to the fact that a dynamic torque has equivalent values to work done / energy over a rotation of one radian, which as a rate then directly relates to power output. All I see after that is a pedantic interaction where the initial point was lost through not seeing the wood for the trees.

[albertw]

Originally Posted by aerobod

The thing is for us pedants (and you have to admit that we both fall into that category) is that equivalent and equal are not the same thing. When talking about the equivalent values as has been the case in relating Nm values of dynamic torque when an angular displacement happens and energy in Joules, there is equivalence in values. No mention or intention to imply torque=energy.

Returning to the beginning and the point of the thread was shift points and what happens from a torque perspective when moving from 4 to 5 and the relationship between torque and power and how it is easy to calculate torque and power in SI units due to the fact that a dynamic torque has equivalent values to work done / energy over a rotation of one radian, which as a rate then directly relates to power output. All I see after that is a pedantic interaction where the initial point was lost through not seeing the wood for the trees.

That's not how I see the discussion. I saw a person who had both the torque and horsepower curves in front of him and asked how to interpret them to choose the best shift points.

Explaining how to convert from one to the other is pretty well useless information for someone who has both plots already and isn't sure how each plot can be used to choose shift points. Noting that the conversion is easier in one set of units is even more useless. Adding that torque and energy have the same units as if that should make a difference to how to choose shift points is just obfuscation. (Well, it was useful in pointing out an error in one of the posts, I'll grant you that, but I wanted to make it clear that it contributed nothing to the original question.)

I was trying to minimize confusion by pointing out the extraneous information. I admit that my rant about how journalists contribute to the confusion surrounding this issue was extraneous information.

I also admit that much of what I posted was pedantic. My justification is that your posts are always interesting but often cryptic and I like to be sure I agree with you or understand fully why I don't.

[XutvJet]

After years of experience modding cars, dynoing them, drag racing them, calculating shift points and trying them out at the strip, it's pretty easy now to look at a dyno plot and estimate the ideal shift points.

I won't pretend that I understand the complete science regarding torque, but I understand power curves and gearing quite well. Where determining ideal shift points gets a bit more complex is with cars with minimal torque, peaky power bands, and poor gearing. For cars like this, the shift points can be quite different depending on gear. On well-sorted late model turbos and cars with fat and broad torque curves, determining ideal shift point is quite easy.

The shift point calculator is merely an estimator, but it will usually get you within a 1 to 2 mph of maximum 1/4 mile trap speed. I don't consider 1/4 mile elapsed time (ET) because that is very dependent on the launch and first 330' of a drag race. Trap speed is the indicator of both available power and how well you've determined your shift points. If traps speed falls between runs, then you know you're either shifting too late or too early.

The biggest mistake I see people make is shifting too early. They assume peak HP is where you shift. Or when they start "feeling" power fall off, then it's time to shift. That's not necessarily the case. I've had plenty of cars that felt like the were wheeshing in the upper rpm and it was time to shift, but doing so greatly impacted 1/4 mile trap speed, sometimes up to 3mph. That's HUGE. Gauging by seat of the pants isn't necessarily telling of the truth. I constantly read on this forum that the M235 N55 "has not power" above 6000rpms and that's where you should shift. That's completely wrong. Peak power happens around 6000-6200rpms, but over 90% of the power is still carried through 6600-6700rpms.