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  #31 (permalink)  
Old 09-06-2013, 06:47 PM
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This is directly from the wikipedia article on torque:

"Mathematically, the equation may be rearranged to compute torque for a given power output. Note that the power injected by the torque depends only on the instantaneous angular speed not on whether the angular speed increases, decreases, or remains constant while the torque is being applied (this is equivalent to the linear case where the power injected by a force depends only on the instantaneous speed not on the resulting acceleration, if any)."

Now the practical argument that's being made here is that say you have two cars of identical weight and design. How about a twin set of 65 Novas?

-Car #1 has 275hp and 400ft lbs of torque thanks to a torquey V8.
-Car #2 makes 300hp and 290ft lbs courtesy of, lets say, a small-displacement DOHC V6.

Let's assume that the V8 probably has a power band that ends somewhere around 4k rpm. The hypothetical V6 has one that makes peak power towards 7k rpm. The argument being made is that even if it doesn't occur off the line, the V6 car will eventually overtake the V8 car because it has more horsepower in an identical platform. The torque in this instance has no bearing on the outcome of the race, only on the beginning.

Now let's introduce mechanical torque multiplication into the above hypothetical situation.

- Car #1 with it's 275 hp V8 is equipped with a th400 and a stock torque converter going through a 2.41:1 gear ratio.
- Car #2 with it's 300hp V6 has a 2.97 t-56 manual transmission with a 4.33:1 gear ratio and the driver is launching at 4k rpm.

This time, even with all of it's rated torque, Car #1 would be left in the dust right from the start. Car #2 has a transmission with a lower parasitic loss, a better gear spread and a more advantageous ring and pinion ratio.

It *is* possible that a car with less horsepower can beat a car with more horsepower, but it's usually attributed to vehicle weight, chassis design, tire design, poor gearing or even just a bad driver. When we eliminate the "what if" factors, it's easy to see that torque is generally irrelevant.

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  #32 (permalink)  
Old 09-11-2013, 12:32 PM
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Really I don't see why matters I'm a torque guy. At the end of the day semis and locomotives bring everything u need to live and they move with double the torque then horsepower
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  #33 (permalink)  
Old 09-11-2013, 12:47 PM
How fast is fast enough?
 
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Quote:
Originally Posted by strokermax View Post
Really I don't see why matters I'm a torque guy. At the end of the day semis and locomotives bring everything u need to live and they move with double the torque then horsepower
and the torque is irrelevant in this scenario too. Which is really hard for some people to understand yet blatantly obvious to others.

If hp and torque was represented in different units I think fewer people would be confused, but people see torque as something that is as significant as hp as they are usually represented with numbers of the same magnitude but the torque is irrelevant. This is shown by your expression "double the torque than horsepower," as if you could in some way directly compare the two (you can't).

It all comes down to applied power.
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Old 09-11-2013, 02:28 PM
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you see in my physics and engineering courses i was taught differently. this is why i say it is not irrelevant. i agree a high revving high hp engine will be faster, but in order to make the hp you need to move the torque higher up in the RPM's to have that high hp its the way i was taught and no matter what the math works out. Most OTR diesels have big displacement low rpm engines and they have to in order to be as efficient and reliable as they are. a high revving high hp diesel would need super low gearing to be useful and the increased rpm would only kill reliability and economy. most locomotives are a bit different since they are diesel electric so there is more to it than gearing and a hp rating. and no matter what all these numbers are just data we can sit here and convert and measure all these units of power and force into different units and achieve the same goal
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  #35 (permalink)  
Old 09-11-2013, 05:12 PM
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I'm talking just basic numbers in every day life a 454 makes more torque then a 302 and most of the time it makes more horsepower too.

Nothing feels like torque putting u back in the seat
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  #36 (permalink)  
Old 09-11-2013, 07:05 PM
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I'm all for big, low rpm engines. I have a 455 Olds in my 1965 C-10. On the street in day-to-day life I would rather have an engine that makes it's power in the lower rpm band. Obviously low rpm engines seem to hold together better and they're easier to live with on the daily because you can run a less radical gear set to drive them. The bigger the engine, the more power it can make at a given rpm compared to a smaller motor. I believe what's being addressed is this statement:

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Originally Posted by ap72 View Post
If you're racing torque is ALWAYS irrelevant, what you're after is power.
When we consider racing, stop-and-go driveability is not a concern, which is where the idea of a "torquey" engine comes from. Even in daily life, the use of the transmission and rear differential itself negates the idea of torque being the important figure. If torque was so important, we would just use a big, low rpm engine to directly drive a wheel, with no gearing in place. Mechanical torque multiplication is what will put the power your engine makes to use.

Now as far as a big diesel goes, Those trucks use quite a bit of mechanical torque multiplication to make the most of their power as well. Here's a link that shows that ratios a transmission in a semi truck would use to keep it in it's narrow power band:

Eaton Fuller 18-Speed Transmissions

a first gear of 14:1 is pretty serious torque multiplication right there. Even the sm420 only has a first gear of 7:1 and that's really low for a passenger vehicle.
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  #37 (permalink)  
Old 09-12-2013, 07:39 AM
How fast is fast enough?
 
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Originally Posted by strokermax View Post
I'm talking just basic numbers in every day life a 454 makes more torque then a 302 and most of the time it makes more horsepower too.

Nothing feels like torque putting u back in the seat
Try swapping out the gears in your differential.
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  #38 (permalink)  
Old 09-12-2013, 07:44 AM
How fast is fast enough?
 
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Originally Posted by monster76 View Post
you see in my physics and engineering courses i was taught differently. this is why i say it is not irrelevant. i agree a high revving high hp engine will be faster, but in order to make the hp you need to move the torque higher up in the RPM's to have that high hp its the way i was taught and no matter what the math works out. Most OTR diesels have big displacement low rpm engines and they have to in order to be as efficient and reliable as they are. a high revving high hp diesel would need super low gearing to be useful and the increased rpm would only kill reliability and economy. most locomotives are a bit different since they are diesel electric so there is more to it than gearing and a hp rating. and no matter what all these numbers are just data we can sit here and convert and measure all these units of power and force into different units and achieve the same goal


I think the point you're trying to make is that higher power equates to a faster car, torque is irrelevant, and lower RPM equates to better durability? I don't think anyone will argue that.
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  #39 (permalink)  
Old 09-13-2013, 10:58 AM
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A good example is the 1991 L98 Vette, and the 1992 LT1 Vette

1991 250hp@4000rpm 350lb/fttorque@3200rpm

1992 300hp@5000rpm 335b/ft!btorque@4000rpm

Both C4, both use the 700r4 trans, the LT1 is a much quicker car through any distance and is a faster car through any distance, even thoughj the LT1 makes less torque the L98 does.

Torque is a static measurement of how much work the engine can perform, while horsepower measures how quickly that work can be done.

Interesting topic for sure.

peace
Hog
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  #40 (permalink)  
Old 09-21-2013, 11:50 AM
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Yea but if u change gears and that kinda stuff Ur adding more to the equation. That's saying 3.54s are faster then 4.10s well duh
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  #41 (permalink)  
Old 09-21-2013, 08:40 PM
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Quote:
Originally Posted by strokermax View Post
Yea but if u change gears and that kinda stuff Ur adding more to the equation. That's saying 3.54s are faster then 4.10s well duh
Quicke? Maybe. Faster? All else being equal, no.
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