BHP vs Torque: Difference and Comparison

Physics is a subject which can easily fascinate a science lover and also questions. Being a tricky subject, Physics tends to baffle and perplex us.

One can get lost in confusion if the terms in Physics are not completely understood. One such confusion is BHP and Torque. Although both are useful in measuring force, they are fundamentally different.  

Key Takeaways

1. Brake horsepower (BHP) measures an engine’s overall power output, while torque represents the force available at a specific engine speed.
2. BHP is a function of torque and engine speed, meaning that an engine with high torque at low RPMs can produce high BHP at higher RPMs.
3. Torque enables quick acceleration and the ability to tow heavy loads, while BHP is more relevant for achieving top speeds and passing power.

BHP vs Torque

The difference between BHP and Torque is that BHP stands for Brake Horsepower and is a unit to measure the power of an engine, neglecting the noise and heat loss, on the other hand, Torque is defined as the magnitude of force measured from the axis of rotation.   

BHP or Brake Horsepower is considered as the engine’s total output in terms of a car. It is also referred to as the rate at which work is done.

It is a sub-type and modification of Horsepower measured by a brake type load- dynamometer. Horsepower is the output of an engine, including the noise and heat losses.  

Torque, on the other hand, is the moment of force or rotational force. Force in linear motion is replaced by Torque in Rotational Motion.

It is also referred to as the rotation of force or mass about an axis. In terms of a vehicle, it is considered as the ability of the vehicle to turn around.   

Comparison Table

Parameters of Comparison	BHP	Torque
Invented/ Discovered By	James Watt	Archimedes
Formula	(Torque×RPM)/5252  RPM-Rotations Per Minute)	R×F or RFsintheta
Symbol	BHP/ HP	Tau (Greek Letter) or M- Moment of Force
Unit	Watt or J/s- Joules Per Second	Newton-meter (N-m)
Measured By	Dynamometer	Torque Meter

What is BHP?  

As aforementioned, BHP or Brake Horsepower determines the output of an engine overlooking the heat losses. It originated from Horsepower but is more efficient than Horsepower as HP determines output, including all the losses.

Brake Horsepower manifests to be essential in the brake system of a vehicle.   

In terms of a car, BHP calculates the Horsepower of the engine of the car peculiarly, excluding the gearbox and generator loss.

Usually, in Horsepower, torque is measured with a torque converter, whereas, in Brake Horsepower, no auxiliary tools are required to measure the torque, hence BHP is considered to be more efficient than HP. SI unit of BHP is Watt or Kilo-watt.  

Brakes are a specially designed segment of an automobile that provides braking force equivalent to the load of the automobile to maintain it at a particular rotational speed.

Thus, BHP is also referred to as the Braking Power of an automobile. BHP is highly specific and is measured from a particular location in the automobile, such as the Rear axle, Rear wheel, Crankshaft, Output Shaft, etc.

BHP in bikes is similar to BHP in cars. In bikes, BHP is calculated as the torque generated transmitted to the wheels. High transmission leads to high BHP.   

If an automobile shows low BHP, that means it can pull off heavy load, on the other hand, if it shows high BHP, that means it can travel and accelerate faster.

In the former American standards, BHP was referred to as Gross Horsepower, which signifies their calculation and test without additional components, whereas in current American standards, it is referred to as Net Horsepower, which denotes that it tests including all the additional components.   

Testing BHP in a car is extremely simple and can be done in two ways with the right components, and one way is to run the engine on a testbed, and another is to run the car on a rolling road and calculate the power transmitted to the wheels.

Nevertheless, nowadays, BHP is extremely useful in understanding automobiles.  

What is Torque?  

As mentioned above, Torque, in simple terms, is a rotational force, is a 3-dimensional force and is calculated for a rigid body.

The Moment of Inertia in Torque is equivalent to Mass in Force. In technical terms, torque is defined as the cross-product of the position vector and the force vector.   

Torque is also defined as the resultant moment of a couple or the rotation around the perpendicular axis. In layman’s terms, torque indicates the capacity of an automobile to turn on a curved road.

The SI unit of Torque is Newton-meter, although The United States Torque is referred to as Inch-pound or Foot Pound.  

Torque and Pseudo Force are responsible for the outward pull we feel on a twisted and curled road or the backward pull we feel when the vehicle is accelerating.

It is essential to understand the concept of torque to understand the banking of road and well of death.   

In terms of automobiles, especially cars and bikes, high torque denotes the high capacity to carry the load, while low torque signifies that the vehicle can travel faster.

Torque is measured using a Torque Meter (Transducer used for torque measurement) or Torque Converter, but varying Torque output is easily measured with the help of a dynamometer.  

Typically, Steam Engines and Electric Motors have the maximum torque so that they can carry enough freight, on the other hand, certain bikes have the lowest torque so that they can accelerate at lightning speed.   

Main Differences Between BHP and Torque  

1. BHP is used to calculate the power output of an engine, while Torque is the rotational force of the wheels of an automobile.   
2. BHP is used to measure the peak speed, while Torque signifies the ability to carry the load and accelerate.   
3. The SI unit of BHP is Watt or J/s, whereas the SI unit of Torque is Newton-meter.  
4. BHP is location specific and is calculated from a single location, in contrast, Torque is non-specific.
5. BHP is a derived quantity that is derived from RPM (Rotations per minute) and torque, while Torque is a fundamental physical quantity.   
6. BHP can be calculated with the help of Torque but cannot be measured individually, while Torque can be measured.   
7. The Dimensional Formula of BHP is M¹L²T^-3  on the other hand, the dimensional formula of Torque is M¹L²T^-2.

References

1. https://link.springer.com/chapter/10.1007/978-1-4615-3594-2_4 
2. https://meridian.allenpress.com/rct/article-abstract/42/4/1014/87981