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Old 04-04-2007, 02:45 PM   #46
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Quote:
Originally Posted by PontiacFan27
My apologies. 16x the distance.

Anyway, you're right. I totally ****ed up the math on that one. I'll reiterate.

A 10' wheel would move 31.4 feet per rotation, whereas a 15" car wheel would move 3.9' per rotation. Which is 8x the distance.
Now the math is correct, but it's based on incorrect facts. How many cars drive down the road on their wheels? Answer. Not too damn many. Most of them in my experience have tires mounted which increases the diameter to somewhere in the 28ish inch range. Pay attention to the details and resubmit.
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Old 04-04-2007, 03:27 PM   #47
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Quote:
Originally Posted by PontiacFan27
I think the guy who wrote that article is forgetting about the size of the wheel acting as a torque multiplier. A wheel that massive wouldn't need nearly as much power to move as fast. Lets say that water wheel was 10' in diameter. Thats 120 inches. Meaning it would move 8x farther in one rotation than a 15" car wheel. To elaborate further, it would move 78.5 feet in one rotation compared to 4.9 feet of the same 15" car wheel.

So, what your saying is, if i smack a mule with a hammer, I can get his attention.
But if I use a longer arm, I can get more attention.

What does that have to do with whether Hp readings are accurate or not?
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Old 04-04-2007, 10:32 PM   #48
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Quote:
Originally Posted by vwhobo
Now the math is correct, but it's based on incorrect facts. How many cars drive down the road on their wheels? Answer. Not too damn many. Most of them in my experience have tires mounted which increases the diameter to somewhere in the 28ish inch range. Pay attention to the details and resubmit.

Do you have to nitpick about everything? Fine, let's say that its 10' with the tire and 15" with the tire.


Quote:
Originally Posted by jcutsh
So, what your saying is, if i smack a mule with a hammer, I can get his attention.
But if I use a longer arm, I can get more attention.

What does that have to do with whether Hp readings are accurate or not?

I'm saying its not unreasonable to believe that the wheel would allow the car it's attached to to move that fast making very little horsepower. That's without transmission gearing taken into account, too.
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Old 04-04-2007, 11:13 PM   #49
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Quote:
Originally Posted by PontiacFan27
Do you have to nitpick about everything? Fine, let's say that its 10' with the tire and 15" with the tire.

.......

What about true tyre rolling radius and deflection?
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Old 04-04-2007, 11:44 PM   #50
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Quote:
Originally Posted by PontiacFan27
I'm saying its not unreasonable to believe that the wheel would allow the car it's attached to to move that fast making very little horsepower. That's without transmission gearing taken into account, too.

Pf, This thread has been about whether the word/term Horse Power was real or imaginary. My point has been no two dyno's produce the same readings, which makes the term Hp rather unscientific. All of the examples have been engines on an engine test stand. There is no car involved anywhere in this thread.

You keep wanting to talk about wheels and tires and transmissions and mama's fried chicken, but the rest of us are talking about the word/meaning and accuracy of Hp. Does the the word Hp have a true meaning?

In the OP "What" stated he had been told Hp was an imaginary number. The rest of the thread was all about why.
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Old 04-05-2007, 01:35 AM   #51
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Quote:
Originally Posted by jcutsh
Pf, This thread has been about whether the word/term Horse Power was real or imaginary. My point has been no two dyno's produce the same readings, which makes the term Hp rather unscientific. All of the examples have been engines on an engine test stand. There is no car involved anywhere in this thread.

You keep wanting to talk about wheels and tires and transmissions and mama's fried chicken, but the rest of us are talking about the word/meaning and accuracy of Hp. Does the the word Hp have a true meaning?

In the OP "What" stated he had been told Hp was an imaginary number. The rest of the thread was all about why.
I was told "i" was an imaginary number too, but it sure comes in handy
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Old 04-05-2007, 02:24 AM   #52
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Quote:
Originally Posted by windsonian
I was told "i" was an imaginary number too, but it sure comes in handy

Thanls Windy,
It only took 51 posts, before someone finally said something that makes sense.
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Old 04-05-2007, 06:44 PM   #53
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So the debate is really about what the unit "horsepower" is based on.
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Old 04-05-2007, 07:16 PM   #54
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Originally Posted by Bronxie
So the debate is really about what the unit "horsepower" is based on.

Welcome back Bronxie.

I have spent a lot of time, making the argument that Hp readings are not accurate. Time I could have spent doing something I enjoy, like sticking my hand into boiling water, or smacking my foot with a hammer. No one here has offered any proof of the accuracy of the Hp value. In fact judging by the comments, many of you donít even know what the discussion was about.

I have spent my life it the field of Instrumentation, I have measured everything from giant tanks of oil and water to micro lever movement of less than 5 millions of an inch. Heck I have even attached sensors to sunflowers to track their degree of movement during the day. All had to be equipped with electronic readouts for human interface. Most of that work was for the EPA, and required everything to be traceable back to the National Bureau of Standards.

The National Bureau of Standards, for those who donít know set standards for everything we measure. They are the organization who determines how long the inch, yard, meter centimeter and all our other measurements are. They control every aspect of volume, weights, and measurements. They are used by the scientific community all over the world.

If I buy a quality scale, I can purchase with that scale a set of test weights. Those weights are traceable back to the NBS. Their accuracy is calibrated to extremely high tolerances. I can use those weights to calibrate my scale, dead on.

I am sure in your tool box you have a set of callipers, with a set of standard length dowels which allow you to check/set the accuracy of your measuring device. Each of those weights/dowels are the same, No matter where in the world, no matter how hot, or how cold.. They will weigh the same or be the same length every time. If I check a bearing surface it will read the same as if some guy in South America read it. It's called standardization.

We can measure the power of an electric motor? The formula is simple, P=I≤R. We can do that anywhere in the world. However, there are some standards we must adhere too. In order to compare our results to a guy in Japan, the accuracy of the Ohmmeter and the Amp meter used must have been calibrated by a lab, to standards set in place by the NBS. Now we have a repeatable result agreed upon by the whole world.

Can we measure the power of a horse, Yes we can. Is it accurate? Yes it is. The reason being, the weights and clock used, are both traceable back to the NBS. No matter where in the world you test that horse the results will be the same.

Can we measure the power of an internal combustion engine? Well, we can sort of. Can we fly that engine around the world testing it in different locations, on different equipment, and get the same accurate scientific results every time? NO. No repeatability.

There are several ways a dyno can be used to measure engine power. Wally and I are familiar with the original water brake, then came the hydraulic brake. All of these system basically apply a force or load which the engine must overcome. We then measure that force and calculate the power and convert it to our measurement, and call it torque. Then we get cute, calculate the torque reading and call it Hp.

The SAE, and ISO have for years since 1970, been trying to come up with an accurate scientific method to measure Hp. It emerges as a topic almost ever single annual meeting. The automotive industry just doesnít want it and fights it tooth and nail. Horse Power sells cars.

They did manage to get everyone to sign on so that they would use Net Hp. In 1990, they again passed an addition which allowed atmospheric calibration on all dynoís. (Joke) I havenít kept up to much after that.

Net-Hp is a attempt by the SAE to bring standards to the world of dyno testing. It states an engine must have all ancillary items in place including the exhaust system to be installed in the car. These same devices be installed on the engine during engine dyno testing.

There is still room to fudge even with this system. Allow me to expand.

I own car company ABC. My competition is company XYZ. XYZ has a new car this year and its engine is rated at 400 Hp. I am building a top of the line auto with all the electrical equipment in the world installed, so it will need a large battery and a giant 120 amp alternator. I install the engine on the stand with alternator, steering pump, pulleys, air conditioner, and exhaust system, and fire it up. That engine will only produce 395 Hp. Now I try everything. I reprogram the computer, and the emissions go out, canít do that. What about new injectors, cost to much. But wait. That big alternator takes 17 Hp to turn, Iíll just replace it with a 60 amp alternator for the test. Ah, now I have 410 Hp. Letís go to press and sell those cars. I know I am going to sell cars with 395 Hp, and I have to put that big alternator in my cars, but it is just so easy to fool that dyno, and the public..

Now I am not against dynoís. They are an excellent tool around the garage. Should I compare my engine against yours with one? HELL NO. A dyno is a tool which will help you tell how much improvement, any changes you have made to your engine achieved. If I add a turbo to my car that dyno will tell me where and approximately how much I have changed the power curve. It will then allow me to set the computer for maximum output. Just how much output is in question. There is no little dowel or weight to attach to a dyno to calibrate it's output. Should Hp be used to sell cars? I donít think so. Not until every dyno is traceable back to the NBS.
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Old 04-05-2007, 11:48 PM   #55
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Quote:
Originally Posted by jcutsh
Welcome back Bronxie.

......

We can measure the power of an electric motor? The formula is simple, P=I²R. We can do that anywhere in the world. However, there are some standards we must adhere too. In order to compare our results to a guy in Japan, the accuracy of the Ohmmeter and the Amp meter used must have been calibrated by a lab, to standards set in place by the NBS. Now we have a repeatable result agreed upon by the whole world.

......

And it's this example Google mechanics can't come to terms with. Every page they open tells them that torque is king and power is made from it. But it's the other way around. Torque cannot exist without power, but power sure exists without torque.... simply looking at the light bulbs in the supermarket will reveal a power consumption rating and it doesn't have any twisting motion. That electric duct heater which provides comfort in your office, does not have any torque association. Go light a camp fire and watch power in action . Grab a battery and bridge the poles with a piece of wire and observe the power.

With an electric motor we can manipulate the torque, but steady state the power consumption. With a generator we can similarly manipulate power output. Even the car alternator has it's output manipulated, not by torque, but by voltage and current regulation... E x I =Watts

The piston action in the car engine is linear, not rotational and it's the brake mean effective pressure that dictates the force, thus torque. That force is generated by combustion gases, expanding because of liberated heat over time, thus power. Linear means no torque.

If you manage to get the incipient knock under control, you can monitor the cylinder pressures and get a pretty good idea of power production within the engine. You can monitor EGT and CHT and apply simple formulas to gain a resultant net engine power. You can also monitor the fuel consumption and AFR, CO gas, etc, apply specific heat constants and calculate the gross power.

With a car the process of velocity and acceleration starts with a linear piston motion and ends in a linear car motion. In between are rotational bits 'n bobs. Linear motion does not equate to torque, but power.....simple.

How do we measure torque? Well we measure it by tractive effort or strain, depending on the measuring device. This is not a direct torque measurement, repeat this is not a direct torque measurement and the actual measurement must have constants and variables applied to gain a "derived" torque figure. We could just as easily skip that and apply constants and variables to deliver a power figure.

On an electric motor we can easily Directly measure power with a watt meter, no matter what it's size, but measuring torque requires interpretive maths i.e. Derived
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Old 04-06-2007, 02:56 PM   #56
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Quote:
Originally Posted by What
Which is more important for maximum "sports" performance? Which would you rather have in your sports car...240 hp engine with 160 lb-ft torque or a 160 hp engine with 240 lb-ft torque? Which will accelerate the fastest?

This was the question. The arguments about which is or isn't the real measurement or which we CAN measure, or how, is irrelevant. Which of the two scenarios is more important to you and why. John missed it right from the start and started arguing irrelevancies.

In the automotive world, in a street car, which of these combinations, as discussed in their traditional roles in the automotive world, is more important and why? Anything else is simply mental masturbation.

No need for other specifics, as it's easy to tell general powerband trends by looking at the figures, knowing how "torque" and "hp" are traditionally related in the automotive world (not electric motors and light bulbs).

On the street, the latter would be more tractable and feel quicker, especially from a stop or out of slower corners, the latter would be more peaky and would be faster. There is no mention of variable valve timing and the like to make the former have a flat 150+ lb ft over a wide rpm range, just a simple relationship. The first might be an S2000 engine, the second a GM V6. the latter would do a better job of hauling mass, while the former would be better for hauling ass.
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Old 04-07-2007, 12:38 AM   #57
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Quote:
Originally Posted by ChrisV
....
No need for other specifics, as it's easy to tell general powerband trends by looking at the figures, knowing how "torque" and "hp" are traditionally related in the automotive world (not electric motors and light bulbs).

.......


The thing is that torque calcs are used extensively in electrical motor selection and construction. A torque figure is just a convenient way of representing the power at a certain speed .... an intermediate mathematical step to a solution. Ultimately they come down to power related issues (e.g. current, voltage)

I would feel pretty confident saying that torque has moved from of minor importance pre nineties to flavour of the month because of the internet. I can still recall some mega brainiac revealing the acceleration curve follows the torque curve... well duh. Then another Einstein come out with the area under the curve revelation... well golly gee fascinating elementary mathematics worthy of a Nobel prize. A ground breaking revelation that, given a common x and y axis, a torque curve will intersect a power curve at the exact same x intercept as the common divisor... well glory be to God, what a conundrum, why don't they teach you that at school.... hang on they do in year 8.

And the last few years torque has taken on celebrity status as a single entity that the rest of popular physics relies on, just ask any car enthuisiast who wouldn't know a parallel wedge from left handed screwdriver.

Torque is a scalar value that has no need for magnitude: a torque engine has massive stump pulling power, while a power engine has no guts, but can rev to 18000 rpm. Thus the comments like "a V8 has more torque than a four pot screamer", because we all know that a longer stroke V8 means we have more leverage and more leverage means more torque, thus a V8 is a torque engine. This must be true because the internet forums tells me so. Just like a diesal has more torque because it has a longer stroke right?
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Old 04-07-2007, 02:15 AM   #58
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Quote:
Originally Posted by What
This has probably been argued before over the net...but those discussions don't count because I didn't take part in them...therefore they are only theoretical discussions that should have taken place given the vast amount of people that "exist" away from me...whatever. We know the truth.

But anyway, I am a firm believer that horsepower is what matters most for best acceleration. But these old "know-it-alls" at the track who speak not from books, but from experience argue that torque is most important and power is just an imaginary number. I give them numerous facts to support my horsepower belief, they give me these f*ckin' recalled instances. Old people... These are amateur racers, I am "What"...who do you side with?


Seriously, what do you believe and why: torque or horsepower?

Funny how the rest of What's Op was ignored. Is that a theory question at the end of his post?

Even more amazing, He hasn't taken part in the discussion.
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Old 04-07-2007, 09:13 AM   #59
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Quote:
Originally Posted by ChrisV
......................
On the street, the latter would be more tractable and feel quicker, especially from a stop or out of slower corners, the latter would be more peaky and would be faster. There is no mention of variable valve timing and the like to make the former have a flat 150+ lb ft over a wide rpm range, just a simple relationship. The first might be an S2000 engine, the second a GM V6. the latter would do a better job of hauling mass, while the former would be better for hauling ass.
i like how you explain that!!!
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Old 04-07-2007, 03:24 PM   #60
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So high torque engines w/ relatively low hp can physically do a lot of work but can not do it very quickly...?


I suppose that's why getting a car off the line or from a dead stop is where torque will have a large impact, ie, "city driving".


Everyone talks about how torque @ low rpms is easier for driving around town.
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