Cummins vs. Powerstroke
Diesel Bomber
Joined: Mar 2007
Posts: 2,015
Likes: 102
From: Nanaimo, BC Canada,
Matt,
As much as I too respect your opinion;
Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. In this case, you'd have expended one horsepower-minute of energy.
Horsepower is the imperial (British) unit of power, now replaced by the watt - the new SI unit. One horsepower is the work done at the rate of 550 foot-pounds per second and it is equivalent to 745.7 watts. Horsepower was first used by James Watt, who employed it to compare the power of steam engines with that of horses.
What does that mean? Well, it means that a motor has zero, notta, zlich HP until it has exerted a force (torque) over a specific period of time. So, it all comes back to how efficient is the motor at producing torque (or force or work, if you perfer). If there are many internal losses, such as fighing gravity in what is labelled as a free body diagram, then the efficiency is lost beyond what could be a achieved in zero friction and you are working harder to get the same as what something is that is more efficient.
At the end of the day I think you are close and I think that you and I are talking about the same thing.
As much as I too respect your opinion;
Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. In this case, you'd have expended one horsepower-minute of energy.
Horsepower is the imperial (British) unit of power, now replaced by the watt - the new SI unit. One horsepower is the work done at the rate of 550 foot-pounds per second and it is equivalent to 745.7 watts. Horsepower was first used by James Watt, who employed it to compare the power of steam engines with that of horses.
What does that mean? Well, it means that a motor has zero, notta, zlich HP until it has exerted a force (torque) over a specific period of time. So, it all comes back to how efficient is the motor at producing torque (or force or work, if you perfer). If there are many internal losses, such as fighing gravity in what is labelled as a free body diagram, then the efficiency is lost beyond what could be a achieved in zero friction and you are working harder to get the same as what something is that is more efficient.
At the end of the day I think you are close and I think that you and I are talking about the same thing.
Diesel Bomber
Joined: Mar 2007
Posts: 2,564
Likes: 285
From: Olympic Peninsula
And there's the misunderstanding of what torque is with regards to an engine.
What an engine can do is determined by horsepower, torque ratings are nothing more than a mathematical equation based on horsepower at any given rpm (to give us an idea of how the engine runs ie; high or low rpm power range). For example, a 400 horse 900 torque powered vehicle will do the same work as a 400 horse 400 torque vehicle, given that everything else is equal. Granted, the higher torque engine will most likely be running at a lower rpm, but the fact remains both engines have the same power and capability with regards to work performed.
As far as gravity pulling down on the piston, wouldn't that also harm you when it goes back up? I'm pretty sure gravity has zero to do with the inline vs V argument, especially at anything over 1 rpm.
I respectfully disagree with your beliefs on torque as you have applied them to an engine.
What an engine can do is determined by horsepower, torque ratings are nothing more than a mathematical equation based on horsepower at any given rpm (to give us an idea of how the engine runs ie; high or low rpm power range). For example, a 400 horse 900 torque powered vehicle will do the same work as a 400 horse 400 torque vehicle, given that everything else is equal. Granted, the higher torque engine will most likely be running at a lower rpm, but the fact remains both engines have the same power and capability with regards to work performed.
As far as gravity pulling down on the piston, wouldn't that also harm you when it goes back up? I'm pretty sure gravity has zero to do with the inline vs V argument, especially at anything over 1 rpm.
I respectfully disagree with your beliefs on torque as you have applied them to an engine.
You're right with your argument, just *** backwards with your math. Torque is the force....horsepower is the calculated number. This is physics/engineering/mechanics 101. Re-read your informational source.
Using your logic, which is correct, a 1,000HP Renault 2.5L Formula 1 engine can do the same amount of 'work' as a 1,000HP KTA-1150 Cummins. Eventually....in theory and on paper, it will, however, in 'real life' it will require the correct gearing, liberal speed limits, a very patient and talented driver, and probably triple'd up earplugs with muffs over those. Also, I wouldn't guarantee how long this said 'work' could actually be performed with one of those little grenades.
My above example is quite radical, but has similarities in the diesel world--a 2 cycle 8V92 versus a 3406 Caterpillar. The Detroit makes the same horsepower, although at a higher RPM point than the Cat, due to the reduced torque value. That's why you can lug the **** out of a Cat and have to drive a 2 cycle Detroit like you're mad at it.
This is also a factual representation of how an engine's design directly affects torque output, however there are many more---stroke vs. bore, rod length vs. stroke, rotating weight, valvetrain timing, etc...... I really hope this makes sense.
Remember, when dealing with engines or other rotating objects, the formula is HP = TQ x RPM/5252. It is impossible for an engine to make more HP than TQ below 5,252RPM, it is impossible for an engine's horsepower and torque to numbers to not be equal at 5,252RPM, and it's impossible for an engine to make more TQ than HP above 5,252 RPM. This is due to the mathematics required to calculate the horsepower using the actual measurement of torque, the working force, to perform said math.
Cheers,
Dan
Last edited by Mr. Miyagi; Oct 7, 2009 at 12:50 AM.
Diesel Wrench
Joined: Mar 2007
Posts: 798
Likes: 58
From: Wyoming
My above example is quite radical, but has similarities in the diesel world--a 2 cycle 8V92 versus a 3406 Caterpillar. The Detroit makes the same horsepower, although at a higher RPM point than the Cat, due to the reduced torque value. That's why you can lug the **** out of a Cat and have to drive a 2 cycle Detroit like you're mad at it.
This example points out my understanding of horsepower vs torque. The two engines make the same total horsepower, but the Cat makes more horsepower at lower rpm's thus the higher torque rating due to the math formula. Both engines can do the same work right? They have different power curves, and different torque values but in the end, the horsepower is the same and they can do the same work.
Why does a dynojet or any other type of dyno measure horsepower only if there is not an rpm signal? It seems to me, that with regards to an engine, the only measurable force is horsepower and torque is derived from rpm vs horsepower. I haven't heard of any type of measuring device that calculates horsepower from the torque??? Drag racing is another good example, you can predict how fast something will be to a point just based on weight and horsepower, not the torque.
My understanding of torque numbers for an engine are as a clue as to whether the engine makes horsepower at low rpm's or high rpm's. Show me what I'm missing here
Diesel Bomber
Joined: Mar 2007
Posts: 2,564
Likes: 285
From: Olympic Peninsula
This example points out my understanding of horsepower vs torque. The two engines make the same total horsepower, but the Cat makes more horsepower at lower rpm's thus the higher torque rating due to the math formula. Both engines can do the same work right? They have different power curves, and different torque values but in the end, the horsepower is the same and they can do the same work.
Why does a dynojet or any other type of dyno measure horsepower only if there is not an rpm signal? It seems to me, that with regards to an engine, the only measurable force is horsepower and torque is derived from rpm vs horsepower. I haven't heard of any type of measuring device that calculates horsepower from the torque??? Drag racing is another good example, you can predict how fast something will be to a point just based on weight and horsepower, not the torque.
My understanding of torque numbers for an engine are as a clue as to whether the engine makes horsepower at low rpm's or high rpm's. Show me what I'm missing here
Why does a dynojet or any other type of dyno measure horsepower only if there is not an rpm signal? It seems to me, that with regards to an engine, the only measurable force is horsepower and torque is derived from rpm vs horsepower. I haven't heard of any type of measuring device that calculates horsepower from the torque??? Drag racing is another good example, you can predict how fast something will be to a point just based on weight and horsepower, not the torque.
My understanding of torque numbers for an engine are as a clue as to whether the engine makes horsepower at low rpm's or high rpm's. Show me what I'm missing here
Horsepower is a calculated number.....
Every dyno uses torque and RPM to factor horsepower.....every one....they have to....it is the only way the horsepower calculation is possible with a rotating object. I will save the inaccuracies of a dynojet-style dynamometer for later but for all intents and purposes, this is how they work.I gotta go to work...someone else chime in here......WYATT!!!!!!!
*EDIT*
Ok....this is all I've got right now so if this doesn't work, well, I'm out of ideas.....
A little bit of work (tq) done really, really fast (high rpm) equals X horsepower.
A whole lot of work (tq) done slowly (low rpm) equals X horsepower.
It's all in the math.......horsepower is 'amount of work done over a given time'.....make sense yet?
Cheers!
Last edited by Mr. Miyagi; Oct 7, 2009 at 09:11 AM.
Diesel Wrench
Joined: Mar 2007
Posts: 798
Likes: 58
From: Wyoming
Every dyno I have been around, including load type dynos will only give you horsepower numbers if you do not have an rpm signal. Torque if you do have rpm signal. Please explain how it's possible to measure torque, but not horsepower without an rpm signal? I'm trying to see your point, it just flies in the face of what I've seen first hand.
Diesel Bomber
Joined: Mar 2007
Posts: 2,564
Likes: 285
From: Olympic Peninsula
Every dyno I have been around, including load type dynos will only give you horsepower numbers if you do not have an rpm signal. Torque if you do have rpm signal. Please explain how it's possible to measure torque, but not horsepower without an rpm signal? I'm trying to see your point, it just flies in the face of what I've seen first hand.
Either that, or they are using another method of calculating horsepower, which flies in the face of how it is supposed to be calculated with rotating objects. Some use a linear calculation, which is incorrect, and most of the reason why a diesel pickup's (for example) numbers can vary so much when going from an inertia dyno to a load dyno.
There are 2 basic types of chassis dyno. One type is the inertia dyno. The inertia dyno measures the speed of a an object, spun by the wheels of a vehicle, to come up with horsepower and torque numbers.
The other type is the hydraulic, or 'load' dyno, which measures the horsepower and torque of a vehicle by applying varied levels of resistance (load) to the drive line. Both dynomometer types have their advantages and disadvantages.
Many HP calculation formulas can be found here:
Formulas for quick calculation of horsepower and power
Formulas for quick calculation of horsepower and power
Diesel Bomber
Joined: Mar 2007
Posts: 2,015
Likes: 102
From: Nanaimo, BC Canada,
I don't know about dyno's I've never really cared much except to watch them. Going back to what Mr. Miyagi said,
A little bit of work (tq) done really, really fast (high rpm) equals X horsepower.
A whole lot of work (tq) done slowly (low rpm) equals X horsepower
This is the same as what I said earlier HP is a work over a specified time period.
So you'll have a MASS, an ACCERLATION to make a Force (F=m*a). Then Torque is the Force (F) multiplied by a distance (d) or moment arm as it is called. So, T = F*d. Then HP = that Force (F) * that distance (d) dividide by the number of minutes it is functioning (this is referred to as the period).
So, 33,000 pound feet of Torque every 60 seconds = 1 HP. Put another way, 33,000 pounds of force multiplied by a moment arm of 12" (1 foot) = 33,000 pound feet of TQ. Do that work over a defined period of 1 minute and you get 1 HP.
I'm sorry but physics doesn't lie.
A little bit of work (tq) done really, really fast (high rpm) equals X horsepower.
A whole lot of work (tq) done slowly (low rpm) equals X horsepower
This is the same as what I said earlier HP is a work over a specified time period.
So you'll have a MASS, an ACCERLATION to make a Force (F=m*a). Then Torque is the Force (F) multiplied by a distance (d) or moment arm as it is called. So, T = F*d. Then HP = that Force (F) * that distance (d) dividide by the number of minutes it is functioning (this is referred to as the period).
So, 33,000 pound feet of Torque every 60 seconds = 1 HP. Put another way, 33,000 pounds of force multiplied by a moment arm of 12" (1 foot) = 33,000 pound feet of TQ. Do that work over a defined period of 1 minute and you get 1 HP.
I'm sorry but physics doesn't lie.
Diesel Wrench
Joined: Mar 2007
Posts: 798
Likes: 58
From: Wyoming
I feel like I totally understand the equations between torque and horsepower, maybe I don't, but I am familiar with the math side of things. What I fail to see is how you can measure torque only with an engine. A dyno uses a weight that you spin, you can calculate how much horsepower it takes to spin that weight up to speed, not torque. Even load type dynos can't give you a torque number without knowing the rpm of the engine, because they are measuring horsepower and then calculating torque with the formula. All of this tells me that an engines torque number is simply a picture of where the engine makes horsepower (which is measurable).
Show me something that measures engine torque and then calculates horsepower by engine rpm and that will show a measurement of torque. Maybe there is something out there that does that, but I am not aware of anything like that at all. Every hp/tq measuring tool I know of measures horsepower, and calculates torque, not the other way around.
I think the term torque as applied to an engine is misleading, in that it is not apples to apples twisting force like an electric motor operates, but even those are rated in horsepower.
In summary, my thoughts are that horsepower tells you what an engine can do (not talking longevity, just work that it can do), and calculating torque gives you a picture of how that engine will do that work.
Show me something that measures engine torque and then calculates horsepower by engine rpm and that will show a measurement of torque. Maybe there is something out there that does that, but I am not aware of anything like that at all. Every hp/tq measuring tool I know of measures horsepower, and calculates torque, not the other way around.
I think the term torque as applied to an engine is misleading, in that it is not apples to apples twisting force like an electric motor operates, but even those are rated in horsepower.
In summary, my thoughts are that horsepower tells you what an engine can do (not talking longevity, just work that it can do), and calculating torque gives you a picture of how that engine will do that work.
Diesel Bomber
Joined: Mar 2007
Posts: 2,015
Likes: 102
From: Nanaimo, BC Canada,
There in lies the part that is misleading.
RPM or Revolutions per Minute = minute as described above is the period and the R is how many times it goes around in that period.
The HP is dependant on the Torque value and the RPM. This is either just 5252 (a number calculated by doing some math) or by the math:
POWER = (TORQUE ÷ RADIUS) x (RPM x RADIUS x 2 x pi)
Which equates to:
HP = TORQUE ÷ RADIUS x RPM x RADIUS x 2 x pi ÷ 33,000
You simply can't make HP without Torque. Sorry but you just can't.
RPM or Revolutions per Minute = minute as described above is the period and the R is how many times it goes around in that period.
The HP is dependant on the Torque value and the RPM. This is either just 5252 (a number calculated by doing some math) or by the math:
POWER = (TORQUE ÷ RADIUS) x (RPM x RADIUS x 2 x pi)
Which equates to:
HP = TORQUE ÷ RADIUS x RPM x RADIUS x 2 x pi ÷ 33,000
You simply can't make HP without Torque. Sorry but you just can't.
