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  #16 (permalink)  
Old 09-04-2013, 05:07 PM
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Horsepower is irrelevant, nothing but a generated number used to sell cars.
Looks like someone is suffering from right man syndrome....

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  #17 (permalink)  
Old 09-04-2013, 05:45 PM
How fast is fast enough?
 
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I'd hand you a shovel but it looks like your digging yourself into a hole very well on your own.
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Old 09-04-2013, 08:41 PM
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I don't know if this will help anyone or not, but in case someone is trying to figure things out, Simply put, torque is how much you can do, horsepower is how fast you can do it. So actually NEITHER is ever irrelevant. Depending on what you are trying to accomplish, one may be of more importance than the other, but they both always play a part in the end result. As far as what will be the faster car, that will require a lot more information to be presented, a fast car requires more than a motor, it is a package.


Kelly
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Old 09-04-2013, 11:51 PM
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I have to agree with AP72. It may be a hard concept to overcome at first because we're all probably used to using our performance cars as street/strip vehicles where having a power band that starts around idle-1500 rpm is most beneficial. In a racing application torque deficiencies can be overcome with mechanical gearing. Any considerations for "driveability" are out the window.

It's true that using gearing to overcome a lack of torque is common on the street, but we also have to factor in being able to accelerate from stop light in a reasonable fashion and at a reasonable rpm, as well as maintain a cruising speed at a (relatively) low rpm. That's still not considering vacuum, belt-driven accessories or mileage concerns.

Obviously this is a bit oversimplified reasoning, but I'm sure you guys get the idea.
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  #20 (permalink)  
Old 09-05-2013, 07:10 AM
How fast is fast enough?
 
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Quote:
Originally Posted by Valkyrie5.7 View Post
I have to agree with AP72. It may be a hard concept to overcome at first because we're all probably used to using our performance cars as street/strip vehicles where having a power band that starts around idle-1500 rpm is most beneficial. In a racing application torque deficiencies can be overcome with mechanical gearing. Any considerations for "driveability" are out the window.

It's true that using gearing to overcome a lack of torque is common on the street, but we also have to factor in being able to accelerate from stop light in a reasonable fashion and at a reasonable rpm, as well as maintain a cruising speed at a (relatively) low rpm. That's still not considering vacuum, belt-driven accessories or mileage concerns.

Obviously this is a bit oversimplified reasoning, but I'm sure you guys get the idea.
You forgot about raising the stall, but basically it really is that simple.

If you make your power at 9,000 rpm then you gear and stall it to run around there, and as always torque is irrelevant.
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  #21 (permalink)  
Old 09-05-2013, 01:42 PM
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Originally Posted by ap72 View Post
You forgot about raising the stall, but basically it really is that simple.

If you make your power at 9,000 rpm then you gear and stall it to run around there, and as always torque is irrelevant.
Very true. Please excuse my three-pedal-centric brain.
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Old 09-05-2013, 01:53 PM
How fast is fast enough?
 
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np, I drive a stick most often too.

The stall can be just as or even more important than gearing though, and many people don't realize that.
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Old 09-05-2013, 08:40 PM
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Originally Posted by ap72 View Post
np, I drive a stick most often too.

The stall can be just as or even more important than gearing though, and many people don't realize that.
You're 100% right, but I know that you know all this stuff already. It is worth repeating though. It's not just the fact that it allows the transmission stall at a given RPM, torque converters also act as a torque multiplier as well.
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Old 09-06-2013, 12:52 PM
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Probably wasting my time arguing here but it's my time to waste so here goes.

What happens when you increase torque at any given rpm? A: hp is also increased at that same rpm.

Seems like an assumption is made that you must give up torque to get hp, which isn't quite correct. It's more like you move torque up (or down) the rpm band to get the desired characteristics from the motor.

One of many reasons why torque is not irrelevant.
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  #25 (permalink)  
Old 09-06-2013, 01:23 PM
How fast is fast enough?
 
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Originally Posted by Rhansen View Post
Probably wasting my time arguing here but it's my time to waste so here goes.

What happens when you increase torque at any given rpm? A: hp is also increased at that same rpm.

Seems like an assumption is made that you must give up torque to get hp, which isn't quite correct. It's more like you move torque up (or down) the rpm band to get the desired characteristics from the motor.

One of many reasons why torque is irrelevant.
the assumption isn't made that you have to trade one for the other but that an engine making 200ftlbs and 400hp will run faster than one making 400ftlbs and 200hp. The torque value goes up, but it doesn't matter because its irrelevant.
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Old 09-06-2013, 01:57 PM
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You are leaving rpm out of your example (lets hope that's not irrelevant too). For a motor to make 400 hp and 200 lb-ft it has to rev to ~10500 rpm, assuming these number occur at the same rpm.
The 400 lb-ft and 200 hp motor will reach those numbers at ~2600 rpm.
Two very different motors, almost like comparing a diesel to a gas engine.

BTW what are the units for hp? IIRC it is torque/time
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Old 09-06-2013, 02:03 PM
How fast is fast enough?
 
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Rpm is irrelevant too.

Average power applied to the track for the run. That's it.

It's not nearly as complicated as you think it is.

And yes you can use it to compare a gas engine to a diesel to a steam engine to whatever else.

The the standard unit for power is horsepower, not torque/time.
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Old 09-06-2013, 02:09 PM
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Maybe you could back that up with some math?

The standard unit for power is actually the Watt not horsepower. And they are both expressed as torque/time.
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  #29 (permalink)  
Old 09-06-2013, 03:26 PM
How fast is fast enough?
 
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The auto and mechanical standard is the hp, they even rate electrical motors in hp, not watts. As for math... It's a defined term, there is no math.

You could say that torque is the first or even second derivative of power (depending on how you define torque) but you'll only find that simple calculus expression in a physics text book. If you know the rpm and hp then you can find the torque, but if you know only the power and not the rpm it really won't affect anything because as always the torque is irrelevant.
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  #30 (permalink)  
Old 09-06-2013, 04:14 PM
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and hp or watts are still torque over time.

if you know the torque and the rpm you can find the hp, what is your point? (I know, torque is irrelevant)

since hp varies with rpm, it sure would be nice to know the rpm...

AND if you increase the torque at any given rpm, the hp is also increased, which makes a torque vs hp argument an exercise in futility BUT I am not arguing that - just saying torque is not irrelevant. (or RPM )

E.T.A. I get that you can have torque w/o movement, but that isn't really relevant here.
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