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Old 04-01-2007, 09:19 PM   #31
giant016
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Quote:
Originally Posted by jcutsh
It has been a few year, since I have been involved at this, but at a seminar at Holly carbs, I attended, we were told, "there are 14 different formulas, manufactures use for to determine their HP ratings. That was in the 70's. I'll bet there are more now. Until everyone uses the same method HP is useless.
If I'm not mistaken there's a new standard that all the manufacturers are supposed to be using. I believe the C6 Z06 was the first to go by it, and it ended up picking up 5hp.
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Old 04-01-2007, 09:40 PM   #32
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Quote:
Originally Posted by giant016
If I'm not mistaken there's a new standard that all the manufacturers are supposed to be using. I believe the C6 Z06 was the first to go by it, and it ended up picking up 5hp.

That's interesting. A new standard.
Certified by whom?
A new device or a new formula?
A new Gm standard, or one the whole world will follow.
Please tell us more.
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Old 04-02-2007, 12:16 AM   #33
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The new SAE standard. Honda used it for the new Civic as well.
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Old 04-02-2007, 02:12 AM   #34
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Quote:
Originally Posted by What
Something about this seems....wrong.
nope, sorry ... basic mechanics.
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Old 04-02-2007, 02:15 AM   #35
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Quote:
Originally Posted by PontiacFan27
The new SAE standard. Honda used it for the new Civic as well.

And at the same time this happened.

Surprise! Those horsepower numbers presented in advertising and brochures aren't always accurate. Though manufacturers are supposed to base their horsepower ratings on SAE net standards, they are not completely beholden to it. They often fudge the numbers. Ford and Mazda both recently got in trouble with the Mustang Cobra and the MX-5 Miata, respectively, when they delivered a car that had less horsepower than what they advertised. Ford ended up doing considerable warranty work to bring the numbers up where they belonged, and Mazda re-rated their car and offered to buy back any offended customers' cars. General Motors regularly underrates their engines, most notably the GM LS1 5.7L engine as installed in the F-body (Camaro and Firebird) cars. Mechanically almost identical to the engines installed in the Y-body car (Corvette), the engine mysteriously "lost" 40 advertised horsepower in the F-body chassis. Although this technically is as fraudulent as selling a car with less than the advertised horsepower, no one seems to complain when they get a car with more horsepower than what appears on the spec sheet.

So SAE has a standard , What about the German based ISO standard? Japan and Korea are working on their own, because they don’t trust the other two. We will soon see the new Asian standard.

Until a world wide standard emerges, the word Hp is pretty much useless.
I am through with this thread.
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Old 04-02-2007, 02:32 AM   #36
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Quote:
Originally Posted by jcutsh
Until a world wide standard emerges, the word Hp is pretty much useless.
Unless you're talking about brown sauce. Never much got into it myself... always preferred BBQ.
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Old 04-03-2007, 03:08 PM   #37
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What is hp based on? What is it representing?


I think the basis for hp needs to be agreed upon before it can be calculated.


Even if you based it on torque x rpm / 5252, that's still calculable and you will get universal results, but what is it currently based on?
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Old 04-03-2007, 04:14 PM   #38
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jcutsh just spent the last 3 pages saying it's not based on anything. Not anything consistent anyway.
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Old 04-03-2007, 06:15 PM   #39
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He also missed out on the whole point of the thread, which was, ON THE STREET, which is more important, a car with a high hp figure and low torque figure, or a car with a high torque figure and a lower hp figure? Whether hp is imaginary or not, the effects it has, where it's made, etc, ARE important in both racing and street use, for different reasons. So we talk about them AND we talk about gearing, because in a street car, gearing is what delivers the torque to the ground, so how a car reacts will be based as much on gearing and torque to the ground as what is happening at the crank.

A car with low torque figures and high hp can be geared to multiply the torque to the ground to ACT the same as a car with higher torque figures but lower hp. The difference will be that the car with the higher hp figure will be able to pull longer. Or, it will be slightly slower accelerating, but a bit faster overall if the cars are otherwise the same.

See, John, we need to discuss gearing and how that affects the force that actually moves the car, when discussing street cars and which is more important. And yes, that imaginary, calculated figure is also important, due to what it represents.

Here's a bit from Bruce Augenstein:

Quote:
OK. If torque is so all-fired important, why do we care about horsepower?
Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.

For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-).

On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:

6 HP.

Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.

A car engine has to do more than exert force, it has to maintain force for long periods of time, and not just at one rpm, but be able to accellerate a mass over time and maintain it's velocity. That requires more than just the force of torque. It requires that imaginary, calculated figure.
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Old 04-03-2007, 06:23 PM   #40
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So horsepower does represent something...it just can't be calculated as of right now.
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Old 04-03-2007, 07:00 PM   #41
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Quote:
Originally Posted by ChrisV
He also missed out on the whole point of the thread, which was, ON THE STREET, which is more important, a car with a high hp figure and low torque figure, or a car with a high torque figure and a lower hp figure? Whether hp is imaginary or not, the effects it has, where it's made, etc, ARE important in both racing and street use, for different reasons. So we talk about them AND we talk about gearing, because in a street car, gearing is what delivers the torque to the ground, so how a car reacts will be based as much on gearing and torque to the ground as what is happening at the crank.

A car with low torque figures and high hp can be geared to multiply the torque to the ground to ACT the same as a car with higher torque figures but lower hp. The difference will be that the car with the higher hp figure will be able to pull longer. Or, it will be slightly slower accelerating, but a bit faster overall if the cars are otherwise the same.

See, John, we need to discuss gearing and how that affects the force that actually moves the car, when discussing street cars and which is more important. And yes, that imaginary, calculated figure is also important, due to what it represents.

Here's a bit from Bruce Augenstein:



A car engine has to do more than exert force, it has to maintain force for long periods of time, and not just at one rpm, but be able to accellerate a mass over time and maintain it's velocity. That requires more than just the force of torque. It requires that imaginary, calculated figure.

Advertised Hp doesn't have anything to do with a car.....
The engine is tested on an engine dyno, out of a vehicle, no car involved what so ever.


At no point did I ever mention a car. Nothing wrong with your statements, They just don't apply here.

I am sure you will agree that drive trains can swallow up as much as 30% of applied Hp. Why would advertisers use that figure.

Before we can talk about the street, we have to decide if Hp means anything at all.

How can you compare two pieces of data, when one has no fixed scientific reference?


Oh lost password one,
Ya we measure it. We just pick one of the several hundred methods, and apply.
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Old 04-04-2007, 01:53 AM   #42
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I would suggest you can't accurately measure torque of an engine in the first place. That gives rise to interpretation and thus the various methods of test. In the old days there was brake horsepower, where they measured the change in power by applying a brake. These days they have whizbang dynamometers that have a myriad on operator inputs.

So I question the validity of any comment along the lines of "you can measure torque, but not power". Dynos are just a convenient way of measuring engine power production (work over time) without having to get into a scientific lab situation.
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Old 04-04-2007, 01:52 PM   #43
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Quote:
Originally Posted by ChrisV
He also missed out on the whole point of the thread, which was, ON THE STREET, which is more important, a car with a high hp figure and low torque figure, or a car with a high torque figure and a lower hp figure? Whether hp is imaginary or not, the effects it has, where it's made, etc, ARE important in both racing and street use, for different reasons. So we talk about them AND we talk about gearing, because in a street car, gearing is what delivers the torque to the ground, so how a car reacts will be based as much on gearing and torque to the ground as what is happening at the crank.

A car with low torque figures and high hp can be geared to multiply the torque to the ground to ACT the same as a car with higher torque figures but lower hp. The difference will be that the car with the higher hp figure will be able to pull longer. Or, it will be slightly slower accelerating, but a bit faster overall if the cars are otherwise the same.

See, John, we need to discuss gearing and how that affects the force that actually moves the car, when discussing street cars and which is more important. And yes, that imaginary, calculated figure is also important, due to what it represents.

Here's a bit from Bruce Augenstein:



A car engine has to do more than exert force, it has to maintain force for long periods of time, and not just at one rpm, but be able to accellerate a mass over time and maintain it's velocity. That requires more than just the force of torque. It requires that imaginary, calculated figure.

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.
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Old 04-04-2007, 02:31 PM   #44
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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 now 8 x 4.9 = 78.5. Those are your numbers (also wrong), not mine. If you want to be taken seriously in a technical conversation, you need to pay enough attention to detail to get the simple things correct. You can't even do that. Think, type, submit... Or would you like to elaborate further?
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Old 04-04-2007, 02:33 PM   #45
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Quote:
Originally Posted by vwhobo
So now 8 x 4.9 = 78.5. Those are your numbers (also wrong), not mine. If you want to be taken seriously in a technical conversation, you need to pay enough attention to detail to get the simple things correct. You can't even do that. Think, type, submit... Or would you like to elaborate further?

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.
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