HP VS Torque

[dirtwarrior]

My dad was part of the "real" mechanic from years ago which could diagnose a car by sound or feel. There are so very few left.
On thing I do remember from him I asked the difference between HP and Torque. Th answer is so simplistic and beautiful. Torque definition is a twisting motion but when it applies to HP and torque. torque means the amount of wortk an engine can do. HP means how quickly it can do it.

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[Flyhalf]

And another thing my father used to say.
"In a car YOU FEEL the torque. Not the Hp.

 

[dirtwarrior]

And another thing my father used to say.
"In a car YOU FEEL the torque. Not the Hp.

true to a big dergee

 

[Jaymar]

It has been my observation over the years that this is one of the most misunderstood things amongst all car guys. Turn a screwdriver, that is torque. Hold a board on the end with something balanced on the other end, that is torque (mostly, but bear with me.) Torque is a form of work which is a force applied to an object. Horsepower, or any power really, is an amount of work done over time. You can actually calculate horsepower as a function of torque and RPM, so they aren't two different measurements. One is a function of the other.

 

[Angrey]

Torque is simply force applied at a distance.

Power is energy per unit time.

In terms of automotive performance, torque is how far back in your seat the car can push you, power is how long the car can continue to accelerate and keep you there.

The more torque a car has, the more acceleration it can impart (momentarily). The more power a car has, the further it can maintain that acceleration.

Power is preferred because torque can be achieved through mechanical machine and multiplication (aka gearing). Higher torque simply reduces the amount of multiplication required to be practical/effective.

 

[GregO]

My Great Grandfather worked his late 19th century 80 acre dairy farm with a team of 2 horses. James Watt the inventor of the Steam Engine needed to market steam driven tractors to farmers. James Watt validated and documented the output of a horse so farmers would understand that a 7 Horsepower steam driven tractor did the work of 7 horses.
My Great Grandfather never did purchase a tractor. He was happy with his 2 horsepower team.

Here’s a nice Bed time story for thoses that are interested.
https://en.m.wikipedia.org/wiki/Horsepower

 

[Jackson1320]

In a race Torque is worthless without horsepower. Tractors have hundreds of torque and about 5 horsepower. It don’t really matter how fast you can get to max speed if max speed is 10 miles per hour

 

[Buldawg76]

Torque is the ability to put an object into motion, Hp is the ability to keep that object in motion and continue to accelerate that motion. Another tidbit is that in any ICE engine the torque and HP lines on a graph will always cross at 5252 rpm.

BD

 

[GregO]

In a race Torque is worthless without horsepower. Tractors have hundreds of torque and about 5 horsepower. It don’t really matter how fast you can get to max speed if max speed is 10 miles per hour

Do you west coast guys even know what a tractor looks like ? LOL

Now this is my kinda tractor, it might not have a ground speed of over 20 mph but wheel speed is another thing. 3000+ HP @ 100++ psi boost. Torque what ?

 

[Jaymar]

See, everybody has heard some colloquial story about the difference but we were all out smoking under the bleachers during physics. Horsepower is torque at a speed, they aren't two separate things where one does this and the other that. Horsepower = Torque x RPM / 5,252. That means that any torque measurement at a particular RPM will always equal xx horsepower. An engine that is said to make more torque usually just makes peak power low in the RPM range a la EcoBoost like driving. Down below 5252 RPM the value of torque when given in ft-lbs will exceed the value of power when given in horsepower. Above 5252 RPM the opposite becomes true. Engines that make peak power above that appear to make "more" horsepower a la Coyote type motors making power high in the RPM band but that is simply the relationship of the numbers used for these units.

 

[boB]

Do you west coast guys even know what a tractor looks like ? LOL

Now this is my kinda tractor, it might not have a ground speed of over 20 mph but wheel speed is another thing. 3000+ HP @ 100++ psi boost. Torque what ?

Yep, torque is good! Audi won LeMans (more than once) with a diesel. JCB exceeded 350 MPH at Bonneville running two of their backhoe loader diesel engines.

 

[GregO]

Horsepower = Torque x RPM / 5,252

That is a simplified math formula developed to provide real-time HP readings during a Dyno pull.
The magic is in the number 5,252. No one ever challenges the meaning of that number and blindly follow the myth that HP = Tq. x RPM/ 5252.

 

[Jaymar]

That is a simplified math formula developed to provide real-time HP readings during a Dyno pull.
The magic is in the number 5,252. No one ever challenges that number and blindly follow the myth that HP = Tq. x RPM/ 5252.

Just like people blindly follow that the squareroot of 4 is 2? It's math, it's physics, it's in the very definition of the unit of measure. Power = Force times Distace over Time. 5252 is rounded because of the radian measurement but that's just nitpicking.

 

[TexasRebel]

That is a simplified math formula developed to provide real-time HP readings during a Dyno pull.
The magic is in the number 5,252. No one ever challenges that number and blindly follow the myth that HP = Tq. x RPM/ 5252.

It's a constant that only works with feet, pounds, and minutes.
1 HP = 33,000 ft*lb/min
1 REV = 2π
HP = ft*lb*2π/min/33,000

33,000 / 2π ≅ 5252

If you switch to inches it becomes HP = in*lb*rpm/63,063

 

[GregO]

Here we have a horse used to establish a world wide unit of measure.
RIP James Watt

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