The 2 common internal combustion engines are 2-stroke and 4-stroke engines, do you know how to compare and contrast the four-stroke and two-stroke engines?
The 4-stroke completes a cycle in two crankshaft revolutions, while the 2-stroke completes a cycle in one crankshaft revolution.
Additionally, in some 2-stroke engine, the fuel and oil are mixed.
I only found out there were two-stroke diesel engines when I saw Detroit Diesel, a two-stroke diesel engine.
Click here to read another article on the 2-stroke engine.
Keep reading below for more details.
What Is The Different Between 2 Stroke And 4-Stroke Engine
Many of you have wondered what the difference between a 2-stroke engine and a 4-stroke engine is. After reading this article, I am confident you will be able to understand the differences.
The difference is that the two-stroke engine has only one stroke up and one stroke down, which gives a total of two movements in one engine cycle.
Two strokes up and down in a four-stroke engine give four movements to complete one engine cycle.
- Working principle
The first blow to the two-stroke engine is the compression stroke, followed by a fuel explosion.
The new fuel mixture is pushed into the cylinder in the second blow. In a four-stroke engine, a spark occurs inside the cylinder, which already contains the combustion gases.
2. Spark plug duration
The spark plugs in the two-stroke engine last longer than those in the four-stroke engine. Although two-stroke engines do not have a separate lubrication system, their spare parts can wear out slightly faster than four-stroke engines.
3. Weight differences and expenses
Two-stroke engines are lighter and less expensive because they have a simple construction and no valves.
Four-stroke engines are much more complex in their design and construction; therefore, their production takes longer and is more expensive.
4. Fuel efficiency
Four-stroke engines are much more fuel efficient than two-stroke engines, as they will run only a few miles per gallon. Four-stroke engines are much more fuel efficient than two-stroke engines, as they will run only a few miles per gallon.
5. Environmental friendly
Another thing to remember is that two-stroke engines are responsible for much more pollution due to the burning of oil in their engines. Four-stroke engines are more environmentally friendly.
But for a 2-stroke engine, there will be smoke coming out, which is typical for a 2-stroke engine, where a 2-stroke engine requires a special type of oil.
6. Structure differences
Two-stroke engines are simpler and cheaper to produce than four-stroke engines. It is structurally simple with few components. For example, the cylinder block of a 4-stroke engine is larger than a 2-stroke engine, although it has the same capacity and number of pistons.
7. Mixed oil and fuel
Unlike 4-stroke engines, 2-stroke engines do not have two special chambers for engine oil and fuel. For example, in motorcycles and other two-stroke engines. But exemption of some heavy-duty diesel is still two-stroke engines, e.g., Detroit engine.
What Are The Similarities Between Two-Stroke And Four Stroke Engines
There are plenty of similarities between the 2-stroke and 4-stroke engines. Below, I will mention a few of them.
1. Both 2-stroke and 4-stroke are internal combustion engines. An internal combustion engine uses some energy from burning fuel to move.
The diesel engine and the combustion engine are two examples. The gases produced by the engine are expelled out of the vehicle through the exhaust pipe.
2. Similarities in engine components: The engine components of two- and four-stroke engines, such as the crankshaft, piston, connecting rod, injection pump, injectors, cylinder head, and engine block, are similar.
3. Both pass through the 4 phases: intake, compression, power, and exhaust.
These are the similarities between the 2-stroke engine and the 4-stroke engine.
What Are The 4-Stroke Called In A 4-Stroke Engine
1. Intake stroke
At the beginning of the first cycle, the piston is at its highest point. The intake valve opens and the exhaust valve closes.
The piston moves downward, drawing the gasoline-gas mixture into the cylinder through the intake valve. When the piston reaches its lowest position, the inlet valve closes again.
2. Compression stroke
In the second cycle, the piston moves back to the highest position. The upward movement compresses the fuel mixture. Shortly before reaching the highest point, the spark plug ignites the gasoline and air mixture.
3. Power stroke
The mixture then burns explosively in the third cycle. Due to its sudden expansion, the combustion now does the mechanical work, pushing the piston back down. The gas cools down. Shortly before the lowest point, the exhaust valve opens.
4. Exhaust stroke
In the fourth cycle, the reciprocating piston moves upward again, pushing the exhaust gas out of the cylinder.
Now, the process starts again from the beginning with the first bar.
What Is The 2nd Second Stroke Called In A 4-Stroke Engine
In a 4-stroke engine, the second stroke is called the compression stroke.
During the compression stroke, the piston rises partially up, and the inlet valve closes, allowing the piston to compress the fuel-air mixture.
By the time it is close to the TDC, the spark plug combusts the mixture of air-fule.
During the compression stroke, the piston rises from BDC to TDC, compressing the air-fuel mixture (or just air in diesel engines) in the combustion chamber.
This process increases the mixture’s pressure and temperature, preparing it for the combustion stage.
The length of the compression stroke, the distance travelled by the piston during this phase, is an important factor in engine design.
A longer compression stroke can increase the engine’s compression ratio, improving overall efficiency and performance.
However, the length of the compression stroke must be balanced with other factors, such as the desired compression ratio, the type of fuel used, and engine characteristics.
What Is The Induction Stroke Of 4-Stroke Engine
The induction is the first stroke of the engine.
During the induction, the piston descends, the inlet valve opens completely, and the cylinder fills with air and vaporized fuel.
At the intake stroke, the piston moves downward from TDC to BDC, creating a vacuum in the combustion chamber.
Thanks to this vacuum, the air-fuel mixture—or air, in the case of diesel engines—can reach the combustion chamber from the intake duct, which also opens the intake valve.
The length of the intake stroke and the distance travelled by the piston during this phase are important parameters in engine design.
A longer intake stroke allows a greater amount of air-fuel mixture into the combustion chamber, which can improve engine performance and power.
However, intake stroke design must be balanced with other factors such as engine rpm, airflow, and overall efficiency.
What Is The Exhaust Stroke Of A 4-Stroke Engine
The exhaust stroke is the last among the 4 strokes.
Exhaust Stroke: As the piston rises to BDC again, the burned gases are expelled from the exhaust port.
Before the piston reaches TDC, the intake valve begins to lift from its seat to allow the air-fuel mixture to enter the engine when the piston descends on the next intake stroke.
This phase is crucial for allowing the efficient exit of combustion gases and preparing the engine for the next intake stage.
The length of the exhaust stroke, the distance travelled by the piston during this phase, is an important factor in engine design.
A proper exhaust stroke allows for good exhaust gas evacuation, improving engine performance and efficiency.
Furthermore, the geometry and design of the exhaust ducts and the exhaust valves also influence the exhaust process and the overall performance of the engine.
What Is Stroke In An Engine
What is a stroke? When the engine works, the piston moves back and forth in the cylinder. One upward or downward movement is called a stroke.
Stroke is the journey, the process from one position to another.
The stroke of an automobile engine refers to the piston’s movement from the top dead centre to the bottom dead centre in the cylinder and from the bottom dead centre to the top dead centre.
The vast majority of gasoline engines are four-stroke engines.
A four-stroke engine means that the sum of the processes from top dead centre to bottom dead centre and bottom dead centre to top dead centre is four times.
Different stroke numbers determine an engine’s characteristics in many aspects, such as power, life, and stability.
From the invention of the first engine to the present, the two most widely used engines worldwide are two-stroke engines and four-stroke engines.
Stroke can be divided into 2-stroke and 4-stroke.
A 2-stroke means that one rotation of the crankshaft can complete a working cycle, that is, the completion of suction (the 2-stroke is called scavenging)—compression—power—exhaust.
Two-stroke engines have no valves and use the scavenging holes on the cylinder liner to take in air. The four-stroke engine has valves.
The crankshaft timing gear drives the timing chain (small chain), and the timing chain drives the camshaft to open/close the valves.
What Is The Power Stroke In A 4-Stroke Engine
The power stroke is the third stroke in the stroke sequence of the engine.
The compressed air/fuel mixture ignites when the spark plug ignites at the end of the compression stroke.
This ignition/explosion propels the vehicle forward, turning the crankshaft and propelling the piston down the cylinder bore.
The piston descends the cylinder bore from the top dead centre to the bottom dead centre.
The exhaust and intake valves are closed.
The exhaust gas is now forced into the cylinder by the piston and released via the exhaust valve.
After that, the next working cycle starts from the air intake stroke.
Among these four steps, the suction, compression and exhaust strokes consume power, and only the power stroke provides power.
To ensure that this intermittent working cycle can operate continuously, conventional engines use multiple cylinders to work in turn and the inertia of the crankshaft and related rotating parts to ensure smooth engine operation.
Final Thought
The article compares and contrasts the four-stroke engine and the two-stroke engine. Did you know that the four-stroke engine was first invented before the two-stroke engine?
Don’t forget that the principles of the 2-stroke and 4-stroke are different.
During the intake stroke, which is the first stroke, the piston starts moving from the TDC to the BDC.
During the compression stroke, the piston travels from the BDC to the TDC to compress the fuel/air combination.
Meanwhile, during the power stroke, the actual combustion takes place, and the spark plugs ignite the compressed mixture of fuel and air.
Lastly, the exhaust gases are released from the cylinder during the exhaust stroke.
Click here to read another article on 4-stroke engine.
Is your engine 2-stroke or 4-stroke?