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Applying Torque vs Horsepower

Coolmanfoo

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I understand the differences of torque vs Horsepower on paper but how to apply them in the real world is a different story.

Ford offers a couple power packs. Some give low end torque boosts while the others give high end power. If my thinking is correct a drag racer would want high end power as they spend more time up top and also wouldn't the low end torque lead to more wheel spin during launching?

Whereas someone who does track days would probably prefer the torque to help push out of corners.

Is my thinking at all correct here?
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Petroleum Jesus

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I understand the differences of torque vs Horsepower on paper but how to apply them in the real world is a different story.

Ford offers a couple power packs. Some give low end torque boosts while the others give high end power. If my thinking is correct a drag racer would want high end power as they spend more time up top and also wouldn't the low end torque lead to more wheel spin during launching?

Whereas someone who does track days would probably prefer the torque to help push out of corners.

Is my thinking at all correct here?
No, or at least not in the case of the torque gains offered in the power packs. The lowest rev range that you could ever expect to use in road racing is about 4500rpm, and that is a rare circumstance. Generally, you will want to keep the revs above 5000rpm, so any gains below that point are meaningless.
 

TexasRebel

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They aren't meaningless.

Low end torque gets you into high end power faster. The game is getting that torque to the ground. If you have more torque than your tires can transfer to the ground it's a waste, but as long as you can find traction there is no substitution for low end torque.
 

bluebeastsrt

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I understand the differences of torque vs Horsepower on paper but how to apply them in the real world is a different story.

Ford offers a couple power packs. Some give low end torque boosts while the others give high end power. If my thinking is correct a drag racer would want high end power as they spend more time up top and also wouldn't the low end torque lead to more wheel spin during launching?

Whereas someone who does track days would probably prefer the torque to help push out of corners.

Is my thinking at all correct here?
Basically you are understanding things correctly. If you have no plans to drag or road race. A torque gain down low will be more beneficial. It'll get you away from a stop light quicker.
 
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Coolmanfoo

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No, or at least not in the case of the torque gains offered in the power packs. The lowest rev range that you could ever expect to use in road racing is about 4500rpm, and that is a rare circumstance. Generally, you will want to keep the revs above 5000rpm, so any gains below that point are meaningless.
Okay so my low end torque thinking may be off but what about my horsepower thinking? A drag racer would prefer that top end power right?
 

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Dominant1

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Torque feels good but hp wins races!
 

Rebellion

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You can't really de-couple torque and HP...cuz HP depends on torque and RPM. HP is mathematically derived from torque and RPM values.


In spite of that, torque/HP at higher RPM is what wins races of all sorts, low RPM's matter more for daily driving.
 
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TexasRebel

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think of it this way...

RPM and torque are the independent variables.
RPM is obviously independent, but the torque curve is designed (stroke length, rod:stroke ratio, bore, compression ratio, &c.) into the engine, thus independent.

HP is the dependent variable. Higher torque down in the lower RPM range = more low end horsepower.

you can have an engine that will produce 10,000 HP at 8,000 RPM, but if you don't have the #-ft. down low to get inertia on your side... you stall.

That's why a John Deere 9560R will get off of a line a hell of a lot faster than a Ford GT (low end torque). But the Ford GT will quickly jump ahead (high end HP).

If you take two engines that have equal rated HP numbers, lets say 500 @ 6,500 RPM, in two cars that are identical weight and aerodynamically, but "Car A" puts out 40 #-ft. more torque in the 2,000 RPM range. Car A will beat Car B.
 

Petroleum Jesus

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They aren't meaningless.

Low end torque gets you into high end power faster. The game is getting that torque to the ground. If you have more torque than your tires can transfer to the ground it's a waste, but as long as you can find traction there is no substitution for low end torque.
For powering out of turns, as he specifically stated, low end torque is absolutely meaningless. The lower half of the powerband is never even used in a road race... ever. Sometimes you might get close on a hairpin or if you specifically chose a lower gear on an increasing radius turn, but that's at most 500rpm under power/torque equilibrium and likely partial throttle anyway.
 

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Norm Peterson

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This ↑↑↑

Crudely, what you want to do is maximize the product of overall gearing times torque at rpm, for the rpm that you have to use based on gear spacing. Normally this falls around the HP peak.

A road course car has a greater need for torque lower into the midrange because not all corners taken in 3rd gear (for example) will be taken at the same speed. Some will be taken at speeds theoretically possible in 2nd, but in the slow portion of the corner you'll be using too much tire traction for cornering to support WOT acceleration in 2nd (making the use of 2nd pretty much pointless while adding one or two more opportunities to screw up).


Coolman - if you want to get a whole lot more understanding of torque, HP, and acceleration, consider developing an Excel spreadsheet that computes acceleration at each mph using the engine torque at the rpm for that speed and gearing.

But be forewarned that the more you get into this in an effort for better results, the more things you'll realize you need to consider (and model somehow). Been at this one off and on since I was still in college, and I'm now retired.


picture.jpg



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If you were able to put the new 2017 super duty diesel in an s-550 would your mustang be faster? That engine is rated at 440 hp and 925 ft/lbs of torque!
 
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Coolmanfoo

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If you were able to put the new 2017 super duty diesel in an s-550 would your mustang be faster? That engine is rated at 440 hp and 925 ft/lbs of torque!
While the engine is rated at those numbers I don't think it would be faster because diesel engines rarely Rev above 3k rpm.

But damn almost 1k of torque? That must feel beautiful
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