Four Stroke Engine

what is four stroke engine ?

A four-stroke engine is a type of internal combustion engine commonly used in vehicles and other machinery. It is named “four-stroke” because it completes four distinct phases or strokes in one full cycle.

four stroke engine parts

A four-stroke engine is a complex and precisely engineered system consisting of several essential components that work harmoniously to convert fuel into mechanical energy. Let’s delve deeper into each of these parts to understand their crucial roles in the engine’s operation.

1. Cylinder: The cylinder serves as the central chamber where the combustion process occurs. Made of durable materials like cast iron or lightweight aluminum, it provides the housing for the piston’s reciprocating movement.
2. Piston: Functioning as a vital moving part, the piston moves up and down within the cylinder, converting the high-pressure energy generated during combustion into linear motion. Its constant oscillation drives the engine’s power output.
3. Crankshaft: The crankshaft, a critical rotating component, comprises multiple offset crank throws that transform the piston’s reciprocating motion into the desired rotary motion. This rotational output forms the basis for powering various applications.
4. Connecting Rod: Playing a pivotal role in the power transmission process, the connecting rod links the piston to the crankshaft. As the piston moves, the connecting rod efficiently translates this linear motion into the desired rotary motion of the crankshaft.
5. Intake Valve: Positioned in the cylinder head, the intake valve opens during the intake stroke, permitting the entry of the air-fuel mixture into the combustion chamber. Its precise control ensures optimal fuel intake for efficient combustion.
6. Exhaust Valve: Also situated in the cylinder head, the exhaust valve opens during the exhaust stroke, facilitating the expulsion of exhaust gases from the combustion chamber. Proper timing and sealing are crucial for effective emissions management.
7. Camshaft: As an essential component of the engine’s valve train system, the camshaft is a shaft with multiple lobes or cams. Driven by the crankshaft through timing belts or chains, it controls the precise timing of the intake and exhaust valves’ opening and closing.
8. Cylinder Head: Serving as the upper portion of the engine cylinder, the cylinder head houses the valves, spark plug (in gasoline engines), and fuel injector (in diesel engines). It plays a significant role in sealing the combustion chamber.
9. Spark Plug: In gasoline engines, the spark plug is an indispensable part that initiates combustion during the power stroke by igniting the compressed air-fuel mixture.
10. Fuel Injector: In diesel engines, the fuel injector plays a crucial role in delivering fuel directly into the combustion chamber at precise intervals, ensuring efficient combustion.
11. Combustion Chamber: The combustion chamber is a crucial space within the cylinder where the air-fuel mixture undergoes compression and ignition, leading to the controlled release of energy during the power stroke.
12. Timing Belt or Chain: The timing belt or chain is an important component that synchronizes the crankshaft and camshaft, ensuring precise valve and piston movements at the right moments for optimal engine performance.
13. Engine Block: Serving as the primary body of the engine, the engine block provides a sturdy framework that houses all the cylinders, supporting various components and contributing to the engine’s overall structural integrity.
14. Oil Pan: Located at the bottom of the engine, the oil pan acts as a reservoir for engine oil, ensuring a continuous and reliable supply of lubrication to reduce friction and wear among moving parts.

In conclusion, the intricately designed and interconnected parts of a four-stroke engine work together cohesively, enabling this versatile power plant to efficiently convert fuel into mechanical energy for a multitude of applications, from automotive vehicles to industrial machinery and beyond.

Must Read : Components of IC Engine

working of four stroke engine

A four-stroke engine operates through a series of precisely timed and coordinated processes, known as the four strokes, that complete one full cycle. Understanding the intricacies of each stroke sheds light on the engine’s functioning, which involves the intake, compression, power, and exhaust phases.

1. Intake Stroke:

• The initial stroke commences with the intake valve opening while the piston moves in a downward motion within the cylinder.
• As the piston descends, it creates a vacuum within the cylinder, drawing in a carefully balanced mixture of air and fuel from the intake manifold into the combustion chamber.
• The intake valve then closes at the completion of this stroke, preventing any backflow of the air-fuel mixture.

1. Compression Stroke:

• In the subsequent stroke, both the intake and exhaust valves are closed, and the piston starts ascending within the cylinder.
• As the piston rises, it compresses the air-fuel mixture within the combustion chamber, significantly increasing its temperature and pressure.
• This compression phase is crucial for enhancing the combustion efficiency during the next stroke.

1. Power Stroke:

• At the peak of the compression stroke, the air-fuel mixture is ignited by a spark plug (specific to gasoline engines).
• The spark ignites the mixture, causing a rapid and controlled combustion, leading to a sudden surge in pressure inside the combustion chamber.
• This sudden pressure increase forcefully drives the piston downward, converting the chemical energy of the fuel into mechanical energy, which constitutes the engine’s power and torque.

1. Exhaust Stroke:

• Following the power stroke, the exhaust valve opens while the piston starts ascending again.
• The upward motion of the piston propels the spent exhaust gases out of the combustion chamber and directs them into the exhaust manifold.
• The exhaust gases are subsequently expelled from the engine through the exhaust system, preparing the engine for the next cycle.

By completing these four strokes (intake, compression, power, and exhaust) in a continuous and well-coordinated manner, the four-stroke engine continuously generates power to drive various applications. The crankshaft, connected to the piston via the connecting rod, converts the reciprocating motion of the piston into rotational motion, providing the engine’s output power. The camshaft, driven by the crankshaft, plays a crucial role in precisely controlling the opening and closing of the intake and exhaust valves, as well as the ignition timing, ensuring optimal engine performance and efficiency.

four stroke petrol engine

A four-stroke engine running on petrol (gasoline) is a type of internal combustion engine commonly found in cars, motorcycles, and many other vehicles. It follows the standard four-stroke cycle to convert the energy contained in petrol into mechanical work. Let’s briefly go through the process:

1. Intake Stroke:

• The intake valve opens, and as the piston moves down the cylinder, a mixture of air and petrol is drawn into the combustion chamber.
• The petrol is vaporized and mixed with the incoming air to form a highly combustible mixture.

1. Compression Stroke:

• Both the intake and exhaust valves are closed as the piston moves up the cylinder.
• The air-fuel mixture is compressed, raising its temperature and pressure significantly.
• This compression is essential for achieving efficient combustion during the power stroke.

1. Power Stroke:

• At the top of the compression stroke, a spark plug ignites the compressed air-fuel mixture.
• The spark causes rapid combustion, and the mixture’s energy is converted into a high-pressure explosion.
• The force of the explosion pushes the piston down the cylinder with great force, generating power.

1. Exhaust Stroke:

• After the power stroke, the exhaust valve opens as the piston moves up again.
• The upward motion of the piston expels the burnt exhaust gases from the combustion chamber into the exhaust system.
• The exhaust gases are then directed out of the engine.

This completes one full cycle of the four-stroke engine. To keep the engine running continuously, the process repeats thousands of times per minute, providing the necessary power to propel the vehicle.

Four-stroke petrol engines are widely used due to their efficiency, lower emissions, and ease of use. They offer good fuel economy and generally produce fewer harmful pollutants compared to some other types of internal combustion engines, making them a popular choice for various applications in the automotive industry and beyond.

four stroke diesel engine

A four-stroke diesel engine is another type of internal combustion engine commonly used in various applications, including vehicles, industrial machinery, power generators, and marine propulsion. It operates on the same four-stroke cycle as the four-stroke petrol engine, but with some differences in the fuel and ignition process. Let’s explore the working of a four-stroke diesel engine:

1. Intake Stroke:

• The intake valve opens, and as the piston moves down the cylinder, only air is drawn into the combustion chamber.
• Unlike petrol engines, diesel engines do not use a spark plug for ignition. Instead, the air is compressed to a high temperature and pressure during the compression stroke, causing spontaneous ignition of the diesel fuel.

1. Compression Stroke:

• Both the intake and exhaust valves are closed as the piston moves up the cylinder.
• The air inside the combustion chamber is compressed to a high pressure, significantly increasing its temperature.
• Due to the high compression ratio, the air becomes hot enough to ignite the diesel fuel without the need for a spark plug.

1. Power Stroke:

• At the top of the compression stroke, diesel fuel is directly injected into the highly compressed hot air in the combustion chamber.
• The heat of the compressed air causes the diesel fuel to auto-ignite, resulting in a rapid and controlled combustion.
• The combustion generates a high-pressure explosion, forcing the piston down the cylinder with tremendous force, producing power.

1. Exhaust Stroke:

• After the power stroke, the exhaust valve opens, and the piston moves up again.
• The upward motion of the piston pushes the burnt exhaust gases out of the combustion chamber and into the exhaust system.
• The exhaust gases are then expelled from the engine.

This completes one full cycle of the four-stroke diesel engine. Similar to the four-stroke petrol engine, the process repeats continuously to provide the necessary power for the engine’s intended application.

Four-stroke diesel engines are known for their robustness, fuel efficiency, and ability to generate high torque at lower RPMs. They are commonly used in heavy-duty vehicles, construction equipment, ships, power generators, and other applications where high efficiency and reliability are essential.

application of four stroke engine

Four-stroke engines have a wide range of applications due to their efficiency, reliability, and versatility. Some of the common applications of four-stroke engines include:

1. Automotive Vehicles: Four-stroke engines are widely used in cars, trucks, motorcycles, and other road vehicles. They provide the power needed to propel the vehicle, whether it’s a small family car or a heavy-duty truck.
2. Motorcycles and Scooters: Many motorcycles and scooters use small displacement four-stroke engines, as they offer better fuel efficiency and lower emissions compared to two-stroke engines.
3. Marine Propulsion: Four-stroke engines are extensively used in boats and ships for propulsion. They are capable of running on various fuels, making them suitable for different marine applications.
4. Power Generators: Four-stroke engines are commonly employed in portable and standby power generators. They provide a reliable source of electricity during power outages or in remote areas without access to the grid.
5. Lawnmowers and Garden Equipment: Many lawnmowers, garden tractors, and other small garden equipment are powered by four-stroke engines, as they are more fuel-efficient and produce less noise compared to two-stroke engines.
6. Agricultural Machinery: Four-stroke engines are used in various agricultural machinery, such as tractors, tillers, and harvesters, to perform tasks like plowing, tilling, and harvesting crops.
7. Construction Equipment: Construction machinery like bulldozers, excavators, and loaders often use four-stroke engines to perform heavy-duty tasks on construction sites.
8. Industrial Equipment: Four-stroke engines are employed in a variety of industrial applications, such as pumps, compressors, and power tools, providing reliable power for various processes.
9. Recreational Vehicles: Motorhomes, ATVs (all-terrain vehicles), and snowmobiles often use four-stroke engines, as they offer better fuel efficiency and reduced emissions, making them more environmentally friendly.
10. Aircraft: Some small aircraft and drones use four-stroke engines for propulsion, offering better fuel efficiency and longer endurance compared to two-stroke engines.

Overall, the four-stroke engine’s widespread application is due to its efficiency, lower emissions, and adaptability to different fuel types, making it a versatile power source for various industries and transportation needs.

advantages of four stroke engine

Four-stroke engines offer several advantages over other types of internal combustion engines, such as two-stroke engines. Some of the key advantages of four-stroke engines include:

1. Higher Efficiency: Four-stroke engines are more fuel-efficient than two-stroke engines. They produce more power per fuel input, leading to better overall fuel economy and reduced operating costs.
2. Lower Emissions: Four-stroke engines produce fewer emissions compared to two-stroke engines. The separate exhaust and intake strokes help ensure better scavenging of exhaust gases, resulting in reduced air pollution and compliance with environmental regulations.
3. Quieter Operation: Four-stroke engines run quieter than two-stroke engines due to the separation of the intake and exhaust strokes, which reduces the noise generated during operation.
4. Longer Engine Life: The design of four-stroke engines, with a separate lubrication system, reduces wear and tear on engine components, leading to longer engine life and reduced maintenance requirements.
5. Improved Reliability: Four-stroke engines are known for their reliability and durability. They are less prone to mechanical failures, making them a popular choice for various applications, including automotive and industrial use.
6. Better Torque at Low RPM: Four-stroke engines produce more torque at lower RPMs (Revolutions Per Minute), which is advantageous for vehicles and machinery requiring substantial power at lower speeds.
7. More Fuel Options: Four-stroke engines can run on a wide range of fuels, including gasoline, diesel, natural gas, and biofuels. This flexibility allows for adaptation to different fuel availability and emission regulations.
8. Simpler Lubrication System: Four-stroke engines have a separate oil system for lubrication, which simplifies maintenance and reduces the chance of oil-fuel mixing, a common issue in two-stroke engines.
9. No Need for Fuel Mixing: Unlike two-stroke engines, four-stroke engines do not require fuel to be mixed with oil before combustion, which makes fuel handling and storage more straightforward.
10. Safer Emissions: Four-stroke engines produce fewer unburned hydrocarbons, which are harmful pollutants and contribute to smog formation, making them environmentally friendlier.

Overall, the advantages of four-stroke engines, such as higher efficiency, lower emissions, and better reliability, have made them the preferred choice for a wide range of applications, from automotive vehicles to industrial machinery and power generation.

disadvantages of four stroke engine

While four-stroke engines offer numerous advantages, they also have some disadvantages compared to other types of engines. Some of the key disadvantages of four-stroke engines include:

1. Complexity: Four-stroke engines are more complex than two-stroke engines due to their valve-train system and additional moving parts. This complexity can lead to increased manufacturing and maintenance costs.
2. Heavier: Four-stroke engines tend to be heavier than two-stroke engines of the same power output. The additional components, such as valves, camshafts, and the lubrication system, contribute to the overall weight.
3. Lower Power-to-Weight Ratio: Due to their heavier construction, four-stroke engines may have a lower power-to-weight ratio compared to some two-stroke engines. This can impact the performance in applications where a high power-to-weight ratio is crucial, such as racing or certain portable equipment.
4. Lower Specific Power: Four-stroke engines typically have a lower specific power output (power per unit displacement) compared to two-stroke engines. As a result, they may require larger displacements to achieve the same power output.
5. Lower RPM Potential: Four-stroke engines usually have lower RPM limits compared to two-stroke engines. This can limit their performance in applications that require high engine speeds, such as racing or certain industrial uses.
6. More Frequent Maintenance: The valve-train system in four-stroke engines requires regular maintenance, including valve adjustments and potential valve train component replacements, which can add to the overall operating costs.
7. Slower Response: Four-stroke engines have a slower response time compared to two-stroke engines, primarily due to the separate intake and exhaust strokes. This slower response can impact acceleration and responsiveness in certain applications.
8. Larger Size: Four-stroke engines may take up more space due to their design and additional components, making packaging more challenging in some applications with space constraints.
9. Limited Lubrication Issues: While four-stroke engines have a separate lubrication system, lubrication can still be a concern during steep inclines or other extreme operating conditions, leading to potential oil starvation.
10. Potential Valve Train Failure: The complexity of the valve train in four-stroke engines can increase the risk of valve-related failures, such as bent valves or valve timing issues, which can be costly to repair.

Despite these disadvantages, four-stroke engines remain widely used due to their overall efficiency, lower emissions, and reliability, which outweigh the drawbacks in many applications. Manufacturers continually work to improve four-stroke engine designs to mitigate these downsides and enhance their performance and durability.

differences between two stroke and four stroke engine

Below is a comparison table highlighting the key differences between two-stroke and four-stroke engines:

Please note that while this table outlines general differences, specific engine designs and technologies may vary, leading to variations in performance and characteristics.

Reference : https://en.wikipedia.org/wiki/Four-stroke_engine