The Basics Behind Car Engine Power
A car engine is the heart of any vehicle, responsible for converting fuel into the power that moves the wheels. In this beginner’s guide, we’ll take a closer look at car engine power and how an internal combustion engine works with an explanation of the car engine measurement units – BHP, HP, kW and PS.
The Genesis Of The Combustion Car Engine
An internal combustion car engine works by a process called the Otto cycle, named after German inventor Nikolaus Otto. The engine consists of cylinders, where a mixture of fuel and air is ignited by a spark plug, causing the mixture to combust. This combustion creates pressure, which pushes a piston down in the cylinder, turning the crankshaft and generating power.
Combustion, otherwise known as burning, is a fundamental chemical process that releases energy from fuel and air combined. This procedure takes place within the internal combustion engine (ICE) itself in order to partially convert the released energy into workable power.
The engine’s operation begins with a cylinder and piston that move in tandem. As the combustion gases expand, they propel the piston which reciprocally rotates the crankshaft. This movement is then transferred through an array of gears to ultimately power your car’s wheels.
Types Of Internal Combustion Engines
Two kinds of internal combustion engines are currently in production today:
- a spark ignition petrol engine
- a compression ignition diesel engine
These powerful machines each run on a four-stroke cycle, which comprises four piston strokes for one complete revolution – intake, compression, combustion and power stroke and then exhaust. With this effective combination of processes put into motion, you can get maximum efficiency out of your vehicle with minimal fuel consumption.
The difference between a spark ignition petrol engine and a compression ignition diesel engine is how they utilise fuel. During intake, a spark ignition engine takes air and mixes it with fuel before introducing it into the cylinder. Afterwards, when the piston compresses this mixture of air and gas, an electric spark ignites these components which result in combustion. The combustion gases propel the piston to move during the power stroke.
Diesel engines, however, will draw air inside where it is compressed. From there, a specific amount of fuel is injected into this hot environment which causes ignition.
How Is Car Engine Power Measured?
When it comes to measuring the power output of a car engine, there are several units of measurement, including the following:
- Brake horsepower (BHP) is the measure of an engine’s power output at the crankshaft before any power is lost through transmission or other components. It is measured using a device called a dynamometer, which simulates the load of the car on the engine.
- Horsepower (HP) is similar to BHP, but it includes power losses through transmission and other components. It is the unit of measurement most commonly used in the United States.
- Kilowatts (kW) is the measure of power in the International System of Units (SI) where one kW equals 1.34 horsepower.
- PS is the German word for horsepower, and it is used in many European countries to measure engine power. Here, one PS equals 0.986 horsepower.
By the official engineering standards, metric horsepower is calculated by measuring the energy required to lift a 75 kg mass one meter vertically in 1 second. After converting it from imperial units, this figure is 1.4% higher than it would have been under imperial measurements. As such, many car makers will choose either PS (Pferdestärke) or HP (Horsepower), based on whichever number is more attractive to potential buyers.
Kilowatts And Kilowatt-Hours For EVs
In the Southern Hemisphere, Kilowatts are almost exclusively used to express car engine power output and are the more modern approach. Considering the meteoric rise of electric vehicles which use kilowatt-hours (kWh) to define how long the engine will be able to produce a specific amount of energy, it probably won’t be long until it becomes the standard across the world.
What Is Torque?
Torque is a measure of the turning or rotational force that an engine produces. It is often described as the “twist” or “pulling power” of an engine and is typically measured in units such as Newton metres (Nm) or pound-feet (lb-ft).
In a vehicle, torque is what propels the car forward. It is the force that is applied to the wheels to make them turn and move the vehicle. The greater the torque produced by the engine, the more force is applied to the wheels and the faster the car can accelerate. Therefore, vehicles with high-torque engines will typically have better low-end acceleration and more pulling power, while vehicles with high-revving engines will have better high-end power.
When choosing a vehicle, torque and engine power are important factors to consider. Cars with high-torque engines will typically be better suited for towing and hauling heavy loads, while cars with high-revving engines will be better for high-speed driving and racing.
How The Modern Car Engine Has Evolved
After variable valve timing and intake runners providing more power and a broader torque curve, car makers have moved toward direct injection to improve performance, fuel economy and reduce emissions.
As many of you may know, there’s more to cars than just the engine as powertrain management has changed everything and automatic transmissions have become a significant part of the equation. The combination of both systems allows for improved overall performance which is most evident in the number of speeds in today’s automatic vehicles that keep engine RPM more consistent when changing gears.
Lastly, to improve engine efficiency and reduce emissions even further, turbochargers and superchargers are becoming more popular. These devices compress air entering the engine so that each power stroke produces more power than with a naturally aspirated engine. This is how today’s modern engines are able to produce far more power from smaller displacements – which has helped reduce emissions while improving performance.
Conclusion
In summary, internal combustion engines work by igniting a mixture of fuel and air in cylinders, creating pressure that turns the crankshaft and generates power. The power output of an engine can be measured using different units of measurement, including brake horsepower (BHP), horsepower (HP), kilowatts (kW), and PS. It is important to note that while they all measure engine power, they are not interchangeable.
At Group1, we strive to bring you the latest in motoring news and we hope that this guide has provided you with a good overview of how a car engine works and why there are different engine power measurement units. To make sure you don’t miss out on anything and stay up to date, simply follow our blog.
