He's really not even worth talking to anymore, he gets the dunce cap of the year award from me.
He's really not even worth talking to anymore, he gets the dunce cap of the year award from me.
Witt
forum member
The dyno calculates horsepower based on roller speed.
The torque you see plotted on a dyno is estimated engine torque at the flywheel. Actual wheel torque is about 4-5 times more than what's on a dyno.
The respective peaks are irrelevant. The respective values at a given rpm are a mathematical fact. Take a better look:
Wow no.
How Does The Dyno Work?
Although due to the miracles of technology it only takes milliseconds for the computer to calculate your horsepower and torque it is not as simple as it may look. It is all just basic laws of physics applied with one another to calculate the measurements. This is a very basic explanation of what goes on inside the computer when you are making a dyno pull, there are a few more details but these are the main points. Lets get started...
First The Computer Must Calculate The Force Force = Mass x Acceleration
"The force required to accelerate an object is proportional to the mass of the object and the acceleration given it."
NEWTON'S SECOND LAW OF MOTION
The torque is the rotational Force the computer is calculating here. The first variable, Mass, is the rotational mass of the two 2700 lb. drums. This is programmed in the computer by Dynojet and due to fact that it is a inertia-type dyno it is a standard variable that can not be changed. The second variable is the acceleration, this is simply how fast you turn over the drums. Just multiply the two together and you have the Force.
Second The Computer Has To Calculate The Work Work = Force x Distance
It is very easy to now find the Work. The computer simply takes the force is has just calculated and multiplies it be the distance you have gone. The distance is nothing more than the circumference of the drum multiplied by how many times it has rotated.
Third The Computer Can Calculate The Power Power = Work / Time
Now the computer takes that Work and divides it by the time taken and you then have your Power or Horsepower as we call it.
See my previous post which shows how UNeducated you are about dynos.
ok. mr wikipedia, do you have any real intelligent/original thoughts?
Still ducking all the facts I see.
PS - not wiki, but how dynos work is common knowledge (to those who aren't idiots)
http://www.speedengineeringanddyno.com/dynoinfo.htm
Grabber
Coyote Snob Member
HP is a Calculation OF Torque. Torque is the physical measurement.
http://www.revsearch.com/dynamometer/torque_vs_horsepower.html
[SIZE=+3]Torque vs Horsepower[/SIZE]
[SIZE=+1]The word horsepower was introduced by James Watt, the inventor of the steam engine in about 1775. Watt learned that "a strong horse could lift 150 pounds a height of 220 feet in 1 minute." One horsepower is also commonly expressed as 550 pounds one foot in one second or 33,000 pounds one foot in one minute. These are just different ways of saying the same thing. Notice these definitions includes force (pounds), distance (feet), and time, (minute, second). A horse could hold weight in a static position but this would not be considered horsepower, it would be similar to what we call torque. Adding time and distance to a static force (or to torque) results in horsepower. RPM, revolutions (distance) per minute (time), is today's equivalent of time and distance. Back to horses, imagine a horse raising coal out of a coal mine. A horse exerting one horsepower could raise 550 pounds of coal one foot every second.[/SIZE]
[SIZE=+1]Here is an example of another way horsepower could be directly measured. Say you have a horse hitched to a plow. In the hitch is a spring scale (like a fish scale). The horse pulls the plow one foot every second and you see 550 pounds on the scale. That horse would be generating one horsepower.[/SIZE]
[SIZE=+1]We see horsepower can be directly measured. However there is a problem directly measuring horsepower of modern day internal combustion engines because they produce rotary motion not linear motion, and unless the engine is geared down, the speed at which they do work (time and distance or RPM) is too great for practical direct measurement of horsepower. It seems logical then that the solution was to directly measure torque (rotational force eventually expressed in pounds at one foot radius) and RPM (time and distance, i.e. distance in circumference at the one foot radius) and from these calculate horsepower. Torque and RPM are easily measured directly. Early dynamometers used a brake device to load the engine. A torque arm was attached to this brake's stator. The brake's rotor was coupled to the engine's crankshaft. A spring scale or other measuring device connected the torque arm to the stationary fixture holding the engine and brake. During a test the brake's application loaded the engine. Torque and engine rpm were observed and recorded. Click here for a description of how this happens on our dyno. [SIZE=+1]On modern day dynamometers horsepower is a calculated value. It's important to remember the dyno measures torque and rpm and then from these calculates horsepower. On the dyno it takes more water flow to the water brake to increase the load on the engine being tested. As the test engine's torque rises more water flow is needed. As the test engine's torque drops less water flow is needed. The dyno's water brake does not respond to Horsepower. Major adjustments to water flow are needed as an engine crosses its torque peak but none are needed as it crosses its horsepower peak. In other words the water flow to the brake during a dyno test follows the engines torque curve and not its horsepower curve. Torque is what twists the tire, prop, or pump. Horsepower helps us understand an amount or quantity of torque. (Torque + time and distance) [/SIZE]
[SIZE=+1]Now if we are measuring torque and RPM how can we calculate horsepower? Where does the equation HP=TORQUE X RPM / 5252 come from? We will use Watts observation of one horsepower as 150 pounds, 220 feet in one minute. First we need express 150 pounds of force as foot pounds torque.
(The * symbol means multiply in the explanations below.)[/SIZE]
[SIZE=+1]Constant (X) = 150 ft.lbs. * 35.014 RPM / 1hp[/SIZE]
[SIZE=+1]35.014 * 150 / 1 = 5252.1[/SIZE]
[SIZE=+1]5252 is the constant.[/SIZE]
[SIZE=+1]So then hp = torque * RPM / 5252[/SIZE]
[SIZE=+1]Here is another way; Remember we know 150 foot pounds and 35.014 RPM = one horsepower [/SIZE]
[SIZE=+1]1hp is to 150 ft.lbs. * 35.014 RPM as X hp is to observed ft.lbs.torque * observed RPM [/SIZE]
[SIZE=+1]Example; We dyno test and observe 400 ft.lbs. torque at 5000 RPM[/SIZE]
[SIZE=+1]1 hp is to 150 ft.lbs. * 35.014 RPM as X hp is to 400 ft.lbs. * 5000 RPM[/SIZE]
[SIZE=+1]When we cross multiply X hp * (150 ft.lbs. * 35.014 RPM) = 1hp * (400 ft.lbs. * 5000 RPM)[/SIZE]
[SIZE=+1]X hp * (5252 ft.lbs. RPM) = 1 hp * (2,000,000 ft.lbs. RPM)[/SIZE]
[SIZE=+1]Divide both sides by 5252 ft.lbs. RPM[/SIZE]
[SIZE=+1]X hp = 1 hp * 380.80[/SIZE]
[SIZE=+1]X hp = 380.80 hp[/SIZE]
[SIZE=+3]Horsepower = torque X rpm / 5252[/SIZE]
[SIZE=+1]Here's an interesting bit of trivia; below 5252 rpm any engine's torque number will always be higher than its horsepower number, and above 5252 rpm any engine's horsepower number will always be higher than its torque number. At 5252 rpm the horsepower and torque numbers will be exactly the same.[/SIZE]
[SIZE=+1]I've been told it also involves something called "radians". (See a definition of radians in the comments link below) I am not an engineer so my explanation may not be technically correct with out using "radians".[/SIZE]
[/SIZE]
http://www.revsearch.com/dynamometer/torque_vs_horsepower.html
[SIZE=+3]Torque vs Horsepower[/SIZE]
[SIZE=+1]The word horsepower was introduced by James Watt, the inventor of the steam engine in about 1775. Watt learned that "a strong horse could lift 150 pounds a height of 220 feet in 1 minute." One horsepower is also commonly expressed as 550 pounds one foot in one second or 33,000 pounds one foot in one minute. These are just different ways of saying the same thing. Notice these definitions includes force (pounds), distance (feet), and time, (minute, second). A horse could hold weight in a static position but this would not be considered horsepower, it would be similar to what we call torque. Adding time and distance to a static force (or to torque) results in horsepower. RPM, revolutions (distance) per minute (time), is today's equivalent of time and distance. Back to horses, imagine a horse raising coal out of a coal mine. A horse exerting one horsepower could raise 550 pounds of coal one foot every second.[/SIZE]
[SIZE=+1]Here is an example of another way horsepower could be directly measured. Say you have a horse hitched to a plow. In the hitch is a spring scale (like a fish scale). The horse pulls the plow one foot every second and you see 550 pounds on the scale. That horse would be generating one horsepower.[/SIZE]
[SIZE=+1]We see horsepower can be directly measured. However there is a problem directly measuring horsepower of modern day internal combustion engines because they produce rotary motion not linear motion, and unless the engine is geared down, the speed at which they do work (time and distance or RPM) is too great for practical direct measurement of horsepower. It seems logical then that the solution was to directly measure torque (rotational force eventually expressed in pounds at one foot radius) and RPM (time and distance, i.e. distance in circumference at the one foot radius) and from these calculate horsepower. Torque and RPM are easily measured directly. Early dynamometers used a brake device to load the engine. A torque arm was attached to this brake's stator. The brake's rotor was coupled to the engine's crankshaft. A spring scale or other measuring device connected the torque arm to the stationary fixture holding the engine and brake. During a test the brake's application loaded the engine. Torque and engine rpm were observed and recorded. Click here for a description of how this happens on our dyno. [SIZE=+1]On modern day dynamometers horsepower is a calculated value. It's important to remember the dyno measures torque and rpm and then from these calculates horsepower. On the dyno it takes more water flow to the water brake to increase the load on the engine being tested. As the test engine's torque rises more water flow is needed. As the test engine's torque drops less water flow is needed. The dyno's water brake does not respond to Horsepower. Major adjustments to water flow are needed as an engine crosses its torque peak but none are needed as it crosses its horsepower peak. In other words the water flow to the brake during a dyno test follows the engines torque curve and not its horsepower curve. Torque is what twists the tire, prop, or pump. Horsepower helps us understand an amount or quantity of torque. (Torque + time and distance) [/SIZE]
[SIZE=+1]Now if we are measuring torque and RPM how can we calculate horsepower? Where does the equation HP=TORQUE X RPM / 5252 come from? We will use Watts observation of one horsepower as 150 pounds, 220 feet in one minute. First we need express 150 pounds of force as foot pounds torque.
(The * symbol means multiply in the explanations below.)[/SIZE]
- [SIZE=+1]Pretend the force of 150 pounds is "applied" tangentially to a one foot radius circle. This would be 150 foot pounds torque. [/SIZE]
- [SIZE=+1]The circumference of a one foot radius circle is 6.283186 feet. ft. (Pi * diameter; 3.141593 * 2 feet) [/SIZE]
- [SIZE=+1]The distance of 220 feet, divided by 6.283185 feet, gives us a RPM of 35.014. [/SIZE]
[SIZE=+1]Constant (X) = 150 ft.lbs. * 35.014 RPM / 1hp[/SIZE]
[SIZE=+1]35.014 * 150 / 1 = 5252.1[/SIZE]
[SIZE=+1]5252 is the constant.[/SIZE]
[SIZE=+1]So then hp = torque * RPM / 5252[/SIZE]
[SIZE=+1]Here is another way; Remember we know 150 foot pounds and 35.014 RPM = one horsepower [/SIZE]
[SIZE=+1]1hp is to 150 ft.lbs. * 35.014 RPM as X hp is to observed ft.lbs.torque * observed RPM [/SIZE]
[SIZE=+1]Example; We dyno test and observe 400 ft.lbs. torque at 5000 RPM[/SIZE]
[SIZE=+1]1 hp is to 150 ft.lbs. * 35.014 RPM as X hp is to 400 ft.lbs. * 5000 RPM[/SIZE]
[SIZE=+1]When we cross multiply X hp * (150 ft.lbs. * 35.014 RPM) = 1hp * (400 ft.lbs. * 5000 RPM)[/SIZE]
[SIZE=+1]X hp * (5252 ft.lbs. RPM) = 1 hp * (2,000,000 ft.lbs. RPM)[/SIZE]
[SIZE=+1]Divide both sides by 5252 ft.lbs. RPM[/SIZE]
[SIZE=+1]X hp = 1 hp * 380.80[/SIZE]
[SIZE=+1]X hp = 380.80 hp[/SIZE]
[SIZE=+3]Horsepower = torque X rpm / 5252[/SIZE]
[SIZE=+1]Here's an interesting bit of trivia; below 5252 rpm any engine's torque number will always be higher than its horsepower number, and above 5252 rpm any engine's horsepower number will always be higher than its torque number. At 5252 rpm the horsepower and torque numbers will be exactly the same.[/SIZE]
[SIZE=+1]I've been told it also involves something called "radians". (See a definition of radians in the comments link below) I am not an engineer so my explanation may not be technically correct with out using "radians".[/SIZE]
[/SIZE]
You're the one ducking facts, I've posted all of the proof I need to.
Grabber
Coyote Snob Member
I think some of the site sponsors like Lethal, BBR, etc. need to share their input on this.
Out of the 4 cars I've had on Dyno's, between Bob Kurgan , Tim @ Norm's, Mike Post, and various other tuners such as Lund, I've always been told that HP is a Calculation and a Result of Torque.
Let's see if some of these guys can chime in and put this to bed already.
Out of the 4 cars I've had on Dyno's, between Bob Kurgan , Tim @ Norm's, Mike Post, and various other tuners such as Lund, I've always been told that HP is a Calculation and a Result of Torque.
Let's see if some of these guys can chime in and put this to bed already.
HP is calculated off of torque. As torque is the base unit of measurement. But if you have a solid HP number, you can also backwards calculate torque.
But Torque is the input to HP. But depending on the dyno you can also just calculate hp through varying means, such as weight of the object spinning the rollers vs. roller speed / rate of acceleration.
A lot of newer dynos use this method for a more accurate torque measure, due to torque multiplication. So in this aspect, it sometimes makes more sense to calculate HP without Torque, then calculate torque from HP and RPM.
It's odd I know, but it's another way of doing it, which is what Witt was trying to convey.
Witt
forum member
Horsepower is nothing more than torque times angular velocity. A dyno measures both and calculates engine torque if an rpm signal is given.
Those who are quoting the internet really do not understand physics or what you are quoting.
So no matter which way it is figured, the respective hp/tq figures at a given rpm are derived, mathematically, from the measured constant?
If this is true (which it is), how could it be inaccurate?
Also, you have yet to address the aforementioned graph which you argue shows 305 hp at the peak tq rpm of 4175, which I helpfully added a few x- and y-axes for your viewing pleasure.
I understand it quite well. I understand it so well, in fact, that I realize that a hp/tq graph is mathematically accurate, at least with respect to hp/tq at the same rpm.
Agree or disagree?
Witt
forum member
No, horsepower is directly measured. Torque is calculated based off another given input, tach signal. Its important to understand that the torque numbers you receive on your dyno printout are not wheel torque which I think is why a lot of people have trouble understanding how a dyno actually works. Its estimated engine flywheel torque reduced by driveline parasitic losses.
Horsepower yes but your torque calcualtion is only as accurate as the tach signal given.
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i skipped alot of the other stuff, but at 4175, isn't about 275 rwhp what i'm seeing?
Most bolton 5.0s are seeing that yes.
Pace seems to think they make about 339 in this case.
I think what pacettr is saying is that the dyno graph shows ~339 HP at peak torque and that your assumption that it is making 305 HP is not substantiated by the graph. I don't believe he's arguing that the dyno graph is an accurate measurement of the power that Nick's car is making. I believe his argument is correct.
Yet you think hp = 305 at 4175 rpm...
I believe you're mistaken.
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I am arguing with pace that peak hp and peak torque are not within 1% of each other. No matter what numbers the dyno is recording.
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