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Old 03-30-2007, 03:37 AM   #16
windsonian
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Quote:
Originally Posted by giant016
I understand what you're saying, but if gears can increase torque, than according to the equation: HP=TORQUE * RPM / 5252, the HP will increase when the torque does. Unless maybe the gears are making the peak torque at a lower RPM.

Side question, what is the term for gears that increase torque but make you lose top speed? I know the ratio is higher (3.23 vs 4.10 for example), but don't think anybody calls them higher gears.
HP = torque x RPM .... you just answered your own question.

Gearing the car increases the torque and lowers the RPM ... net change to HP is canceled.

for example, if your car is geared 5:1 from the crank to the rear axles, you have 5 times the torque there, but 1/5 the RPM. Same power (minus losses)
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Old 03-30-2007, 03:42 AM   #17
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Quote:
Originally Posted by windsonian
HP = torque x RPM .... you just answered your own question.

Gearing the car increases the torque and lowers the RPM ... net change to HP is canceled.

for example, if your car is geared 5:1 from the crank to the rear axles, you have 5 times the torque there, but 1/5 the RPM. Same power (minus losses)
Something about this seems....wrong.
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Old 03-30-2007, 06:58 AM   #18
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Quote:
Originally Posted by giant016
.......Side question, what is the term for gears that increase torque but make you lose top speed? I know the ratio is higher (3.23 vs 4.10 for example), but don't think anybody calls them higher gears.


Think of how far the car goes for each engine revolution. The slower the wheel turns from increased torque mulipication, the shorter the distance covered so the "shorter" the gearing. Conversely the longer the car travels on the road per engine revolution the "longer" ("taller") the gearing.
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Old 03-30-2007, 03:14 PM   #19
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Originally Posted by ChrisV
Nope. Torque is multiplied through the gears to the wheels, while hp is not.

Try this little experiment: start your car in first gear from idle. Now try it again in 4th gear. Why does it accelerate quicker in first gear? Why is the top speed in first gear so low?


Because 1st gear is a small gear, giving it fast acceleration but not allowing for a high top speed (in that gear) and 4th gear is a large gear, not allowing for acceleration but allowing for a high top speed...?



The way I learned was by comparing it to bike gears. The small gears on a bicycle will will allow you to pedal fast because the chain is going around a small circle, and then of course you reach the point where the bike can not physically travel any faster in that gear (when the pedals are spinning faster than you can pedal)... you have to upshift to a bigger gear to go faster.


And then of course, in a bigger gear, the bike will not pedal as fast, but each pedal is more powerful and propels the bike to speed more.



I know I am over-simplifying, but this same concept applies to car gears, right, Chris?




Someone the other day said something which I am not sure if it's correct or not. It was something to the effect of,

"Torque is the actual amount of work your engine can do and HP is how fast it can do that work."

I guess what he was saying was, a big diesel truck engine can do a LOT of work, but it takes it a long time to reach its peak working ability because of low hp... and likewise, an average sports car wouldn't be able to do nearly as much work but would be able to do its maximum work much faster, making it suitable for sports driving.



Thanks Chris
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Old 03-30-2007, 07:07 PM   #20
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I made a stupid a$$ post a few back and not one person called me on it. It was fun making that stuff up though. I am going to try one more time, because I really think children can be taught if the teacher is smart enough. I will never mention it again after this.

Ok kiddies. Man has never invented a device which can measure Hp. . . . . . . .
It just doesn’t exist. There is no mechanical, electrical, or hydraulic way to measure Hp, unless you are a measuring a horse, of course. There are no springs, gears, magic wands, nothing that will produce a signal that represents Hp of ”rotary motion.” We can measure the penis on an amoeba, and how fast a quark moves, but we can’t measure Hp.

Well, how do we get that reading then? DUH!!!

We make up some stuff and calculate it.

Engineers can calculate hp, torque, volumetric efficiency, flame wave traveling rate, and a whole host of other things, before an engine is even built. They use calculations. (Math stuff) Most of those calculations are based on years of empirical data.

We can measure torque, and rpm. A few transducers here, a few strain gages there, maybe a differential pressure transducer, and waa-laaah. Now we have an electrical signal we can send to a meter and give a true torque reading. Rpm is no problem either.

Back in the days when dyno’s first came about, some math genuis said, “Wouldn’t it be nice if we could add a Hp gage to our dyno, and fool the whole damn world into thinking it’s important. All we have to do is use the torque and rpm signals, run them through an amplifier, and hook it to a gage, draw a few numbers on the scale and we have Hp.”

Now before they could do all this a few problems had to be worked out. They needed a simple formula. Then they needed to come up with an amp that could do a little multiplication/division type calculation stuff. No problem, here is the formula.

Horsepower = torque x rpm / 5252

Now this is pretty simple, you can work that out on your pocket calculator and it is certainly close enough for sales ads and magazines and those among us of the lower quality mind. This is much simpler then the three page spreadsheet formula the engineers used to produce their hp numbers. Now you know why different dyno’s produce different Hp results. It’s that damn little amplifier.


Now let’s talk about those sneaky manufacturers. When they list their numbers, where did they come from? Did they use a dyno? Did the engineers calc them? What rpm did they use for torque/hp? There is lots of room to fudge a little here. Remember torque is a true reading. Ford doesn’t believe in the 5252 number relationship. They use their own formula based on radians, which is why their numbers are usually inflated. They paid some guy in engineering $15,000 for that one. It only adds to the confusion.

For those of you with some math skills, let me add this. This is really important. It explains Wally’s excellent points. Read it several times if you have to. If you plot torque and hp on the same graft, they will cross over one another. Here is why.

Below 5252 rpm any engine's torque number will always be higher than its horsepower number.
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. (Any engine)


If we could test an engine the way that steam-engine guy Watts measured horses, I think we would have to throw away all of our Horse power tables. Hp is good for only one thing, making changes to a single engine and determining if those changes produced a desired result.

These are engine spec’s. They have nothing to do with gears, wheels, ash tray’s or Chinese Margarita’s.. Why would anyone even bring those things up in a discussion about Hp.

As the years rolled by, the common man used Hp more and more until it became a standard pushed by the car makers. Gentlemen, we are not common men. We are automotive enthusiasts. We should not allow Hp to be used for anything more then it is. Just a calculated number.

Does an engine that produces 400 Hp really have the power of 400 horses? I have raised horses most of my life. It always amazes me how damn strong they are. I doubt that little engine could even come close to moving the weight 400 horses can.


Wally, I bet you thought I had lost my friggin mind with that last post. Didn’t ya? lol

You other guys can forget my last post. It was all crap.
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Old 03-30-2007, 08:03 PM   #21
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I thought 1 horsepower was equal to pulling 1 pound 32,000 feet, 32,000 pounds 1 foot, or anything in between. So an engine with 100hp could go pull a 1 pound block 3,200,000 feet (606 miles). Wait, but then a human could have 100hp by pulling a 1 pound block 600 miles...I've confused myself lol.
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Old 03-30-2007, 09:55 PM   #22
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Quote:
Originally Posted by chris_knows
I thought 1 horsepower was equal to pulling 1 pound 32,000 feet, 32,000 pounds 1 foot, or anything in between. So an engine with 100hp could go pull a 1 pound block 3,200,000 feet (606 miles). Wait, but then a human could have 100hp by pulling a 1 pound block 600 miles...I've confused myself lol.


Think you're off a bit. It's equivalent to moving 33,000 lbs 1ft in one minute.


Or 330 lbs 100 ft in one minute... or 33 lbs 1000 feet in one minute.

That's what www.howstuffworks.com says anyway.
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Old 03-30-2007, 10:07 PM   #23
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Quote:
Originally Posted by Bronxie
Think you're off a bit. It's equivalent to moving 33,000 lbs 1ft in one minute.


Or 330 lbs 100 ft in one minute... or 33 lbs 1000 feet in one minute.

That's what www.howstuffworks.com says anyway.
Ohh...Thanks. I read it on howstuffworks a couple of years ago, and must have forgotten the "per minute" part lol.
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Old 03-30-2007, 10:18 PM   #24
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Quote:
Originally Posted by Bronxie
Think you're off a bit. It's equivalent to moving 33,000 lbs 1ft in one minute.


Or 330 lbs 100 ft in one minute... or 33 lbs 1000 feet in one minute.

That's what www.howstuffworks.com says anyway.

Let me clear this up Fellows. You are talking linear motion. We can measure that. Just drag a weight across a surface with a scale attached.

Hp for an engine is "rotary" motion. Can't measure that.

Reading is your friend.
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Old 03-30-2007, 11:10 PM   #25
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Quote:
Originally Posted by jcutsh
Let me clear this up Fellows. You are talking linear motion. We can measure that. Just drag a weight across a surface with a scale attached.

Hp for an engine is "rotary" motion. Can't measure that.

Reading is your friend.
So it's inaccurate if that rotary motion is converted to linear motion?
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Old 03-31-2007, 12:11 AM   #26
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Don'r worry John, I already figured you were suffering dementia.
The old taxable horsepower was a better indicator in my books, but pretty poor for bragging rights.

What's wrong with radians? When I size a flywheel I use radians.

Power figures are much more convenient for the various calculations. When we used to test the big diesels we'd hook a generator up to it and load it with a tub. The electrical current gave a pretty good indication of the power output...... no one even talked about torque in those days, but then again the wheel was yet to be invented.
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Old 03-31-2007, 01:14 AM   #27
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First, a clarification: torque is no more real than power. The DOHC puts out 133 ft-lb of ground-pounding torque, but I've seen some older Neons that are leaking torque and you have to avoid driving behind them because the torque, once leaked, is slippery. Don't bother picking it up and adding it to your engine as it degrades quickly and will take you out of Stock class. Consider torque and power as concepts used to describe how things interact to produce movement and how "energy" (another concept) is transferred. -Ed Lansinger

this guy makes some easy to undertsand points....read more at http://www.allpar.com/eek/hp-vs-torque.html this is not advertising but a redirect to help answer a question just so ya know
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Old 03-31-2007, 01:32 AM   #28
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They're both equally important. It really depends on the curve. A high peak of either isn't beneficial if the other is too low, or if the curve is low in general.
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Old 03-31-2007, 03:48 PM   #29
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Quote:
Originally Posted by chris_knows
So it's inaccurate if that rotary motion is converted to linear motion?
How can you prove or disprove that? One you can measure, the other you can't. Science is based on math, backed up by solid scientific experiments. No experiments, the math sucks and is discarded.

There is no approved scientific method to measure rotary Hp. There is nothing listed in the "Engineering Standards and Methods", except a little formula, listed as "may be applied."

Sure we can use a little math. But we can't prove the math is accurate. Since we don't have a set standard, it leaves manufacturers with the choice of selecting any number they choose and advertise it as their HP.

You could say that my red car is faster than your green car, because it has less wind resistance. That would be a rather stupid statement, but it can be tested with real science.

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.

Saying my car has 25 more Hp is stupid also. The is no approved standardized scientific device or method to prove that. Now if you say my car has 35 more ft/lbs of torque, you have a winner. Because there is a torque measuring device everyone in the whole wide big old world agrees with.

If you dyno a car on 4 different dyno's you will get 4 diff Hp readings. You will probably get the same torque readings within 1% on all 4 dyno's. Why is that?

Wally:

Radians are a wonderful tool. Hard to do round engineering without them. I use them every time I get myself a piece of pie or pizza.
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Old 04-01-2007, 07:06 AM   #30
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Yeah, I guess you're right; there is no real way to prove that lol.
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