What is the difference between horsepower and torque?
(What is a really fast car?)



What's New?

1. Torque and Horsepower
   1-1. Introduction
   1-2. Torque
   1-3. Horsepower
   1-4. Summary of basic
   1-5. Experience how to torque up
   1-6. Can not be compared to horsepower and torque
   1-7. Relationship of torque and speed of the drill

1. Torque and Horsepower

1-1. Introduction

Description of torque and horsepower is coming out often in automobile magazines, etc., but the difference between the two is so difficult to understand the sensory, persons are recognized less correctly.

Also, if checking some books at library, esoteric picture and formulas suddenly emerges, and if checking inter-net there is meaningless comment or obviously wrong description.

Therefore, I try to explain easy to understand the difference between them without difficult formula as much as possible.

Also, I try to correct a lot of misunderstanding for the basic characteristics of the car.

Finaly, I would like to try to image quantitatively really fast domestic cars.

I began to write in the above policy, but it has already become long and containing some formulas imperceptibly.

For this reason, please feel free to skip hard section or unnecessary section.

I suppose that there is a part of the smug little, but on the occasion of this article, I hope you are interested in science and math, even a little.

1-2. Torque

At first, the torque is the force of rotation for the tire of the car.

As an example a bicycle, it is force (red arrow in the figure below) that pushes the pedal.

So, the torque is that large, it means that the force that pushes the pedal is stronger.

If the force of pushing the pedal is strong, what happens?

Yes, onset of bicycle is improved. That acceleration will be better.

Also, you can continue with ease even uphill.

1-3. Horsepower

Next is the horsepower.

Torque means just momentary force and horsepower shows that how much performance is represented by continuously working the torque

To be more precise, horsepower indicate that number of horses that can carry how much heavy luggage how long distance in a period of time.

In the case of the bicycle, horsepower will be easily calculated by multiple by the number of rotations of the pedal to the pedaling force .

So what happens in the bicycle if push the pedal strongly and rotate pedal quickly?

You are right, the speed becomes faster.

If we put the luggage on the bicycle it is capable of carrying far in a period of time than a human shoulder.

This is the power of the horse that means horsepower.

1-4. Summary of basic

The following is summary of the above.

Torque is momentary force. If it increases, onset (acceleration) will be better.

Horsepower is continuous power. If it increases, getting much speed and carrying heavier luggage far and faster.

It's is believed that onset (acceleration) is related to horsepower, but it related to torque.

I suppose that everyone find it on the previous bicycle explanation.

To be more intuitive, torque is sprint which compete acceleration, horsepower is marathon which compete speed.

I hope that you understand approximate difference between them.

1-5. Experience how to torque up

Until now, I used a bicycle for the example.

Next, how do you feel the torque in your car, let's mentioned here.

As you are driving and stepping on the accelerator, the car will accelerate.

This acceleration feeling comes from torque and reached speed comes from horsepower.

Would you like feel more torque up?

If so, you can get it without changing the fuel or adding turbo device.

For example, you are driving frat road and approaching long downhill .

Then, your car began to accelerate gradually without stepping on the accelerator.

If you step the accelerator further, you can feel the acceleration much easier from flat road.

That is torque-up.

No matter how heavy car can be accelerated comfortably if it has sufficient torque.

In other words, it is impossible for no matter how light car to accelerate comfortably if there is no much torque.

Did you get the difference between the approximate torque and horsepower?

1-6. Can not be compared to horsepower and torque

Can not be compared to horsepower and torque

Before closing this chapter, I must tell one thing.

In this article, I am going to comparison of the "car of horsepower emphasis" and "car of torque emphasis" later, but this is expressed clearly incorrect.

Because horsepower = torque × rotation speed, if torque goes up horsepower automatically increase.
It does not make sense to compare of both.

For example, sales amount = unit price × sales numbers.

In this case, no one compares sales amount and unit price,

Everyone consider unit price and sales numbers.

If you return to the original story, it described "car of horsepower emphasis" and "car of rotation speed emphasis" is the correct expression.

However, since to give priority to the ease of understanding, please forgive that instead of "car of rotational speed emphasis", I am using the "car of horsepower emphasis" commonly used in this document.

1-7. Relationship of torque and speed of the drill

Reading up to here, you may get relationship of horsepower, torque and rotation speed as the following formulation.

Horsepower = torque × number of revolutions

Away from the car, I want to tell you an interesting story for them here.

You are going to drill a hole of 1mm and 10mm diameter in the steel plate by using a drilling machine.

The Drilling machine can be adjusted to three levels of high / medium / low speed by changing the position of the belt.


In order to get fine results, how do you select the rotation speed for 10mm and 1mm hole?

Think intuitively,

High speed 1mm drill may be broken easily when it contact to the steel, therefore 1mm drill should be slow.

Slow speed 10mm drill may be stopped when it contact to the steel, therefore 10mm drill should be high speed.

They are wrong and opposite.

If 1mm drill rotates slow speed, torque become increase and exceeds the breaking strength.

Therefore, it will break off easily if you strongly pressed 1mm drill against the metal.
So, you must reduce the torque in the high-speed rotation.

If 10mm drill rotates high speed, torque become reduce.

Therefore, it will stop easily if you strongly pressed 10mm drill against the metal.
So, you must increase the torque in the slow speed rotation.

Do you get that even with the same horsepower, work efficiency is different at high torque (low speed) and low torque (high speed)?

1. Torque and Horsepower




What is Torque?

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