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In internal combustion, stroking is the mechanism whereby the pistons in the cylinder go up and down. The process starts with the injection process, in which a mixture of fuel and air is forced into the vehicle’s engine cylinder by the piston’s downward expansion.
The critical distinction between a four-stroke and a two-stroke engine would be that a four-stroke operation completes one power stroke in four phases, or two full revolutions, whereas a two-stroke engine completes one power stroke in two phases or one entire rotation.
Stroke refers to the extent of the piston’s route, hence it’s an element in deciding the engine cylinder volume (which determines the cc of the engine). The successive strokes of a piston, commencing with intakes, compression, expanding, and ending with emission or exhaust, define the stages of an engine’s combustion cycle.
Let us now understand the difference between the two kinds of strokes by various means.
Two-Stroke Engine
To generate power, a 2-stroke motor engine completes two-piston motions (one crankshaft rotation). Because the entry of gas into the cylinders and the emission of remaining gases happen at the same time, the engine may generate power after just a single cycle. The inlet stroke has a valve that releases and shuts in response to changing pressures. However, because it comes into contact with machine components often, the gasoline is mixed with oil to offer lubrication and allow for smooth strokes.
Four-Stroke Engine
Starting with intake, compressing, power, and exhaust, a 4-stroke engine has four sequential stages. Each one corresponds to a whole piston stroke. As a result, for every four-piston cycle, it provides one power stroke, while a full cycle needs two rotations of crankshafts. revolutions of the crankshaft. Today generally in every motor vehicle this four-stroke engine is installed. We’ll see the pros and cons of this in the below sections.
Working of Two-Stroke
The working of a two-stroke engine is done in two movements of the piston in the cylinder. In this case, there are no inlet and outlet valves. However, the air and fuel mixture is in direct contact with the crankshaft.
Stroke 1: In stroke 1, when the piston is currently in a position of compressing the air-fuel mixture or can be said at the top dead centre (TDC), the spark plug is ignited and the mixture burns pushing the cylinder to the bottom dead centre (BDC) when the fresh air mixture gas enters inside the cylinder via the crankshaft through a tubing mechanics. The fresh mixture enters the cylinder pushing the burnt gases outside of the cylinder. This stroke when the piston is moved down is usually called the power stroke.
Stroke 2: In stroke 2, when the piston is at the BDC, the new fresh air-fuel mixture has entered the cylinder and when the burnt gases have been expelled. The piston then moves to the TDC, with the help of momentum gained by the first stroke or the power stroke. When the piston moves upward the fuel mixture gets compressed inside the cylinder and again the igniter ignites and the gas gets burnt and stroke follows.
Working of Four-Stroke
In a four-stroke, the piston moves four times inside the cylinder to complete its one cycle. Where the stroke comprises Intake, Compression, Expansion, and Exhaust.
Stroke 1: In stroke one, the intake valve gets opened and the cylinder moves from the TDC to BDC. Which creates suction inside the cylinder and the fuel mixture moves inside the cylinder.
Stroke 2: During stroke two, the piston moves from BDC to TDC. Compressing the mixture along the way.
Stroke 3: During stroke three, the spark plugs or the igniters get ignited and the fuel mixture burns to create a power stroke and push the piston down forcefully, i.e., from TDC to BDC.
Stroke 4: During the last and the final stroke, the piston moves again from the BDC to the TDC. During this time the burned gases then get expelled from the cylinder by the forced movement of the cylinder to TDC. This completes one cycle of the engine or the otto cycle. Again, after which the cylinder goes to the BDC for intake and the process starts from stroke one.
Advantages and Disadvantages of Two-Stroke
Advantages | Disadvantages |
Simple construction of engine as it does not have any valves | Parts can wear and tear at a faster rate if lubrication is not done properly |
It can work in any orientation | Very less fuel efficiency |
Less Expensive | Produces a lot of pollution and also unburned gases can also escape from the cylinder |
Cheaper In cost | Produces a lot of noise |
Light Weight | The oil of a two-stroke engine is expensive and a large amount is required of those. |
A bigger power boost is generated as a power stroke comes in every 2 strokes of the piston. | A lot of pressure is generated on the crank |
Advantages and Disadvantages of Four-Stroke
Advantages | Disadvantages |
Have high volumetric efficiency over a wide speed range of engine | Complex Engines and their control valves |
Less Noisy | Power generation is less than two strokes as there is one power stroke in every four strokes |
Less wear and tear occur | Costs a higher amount than two-stroke |
Lower emission with higher horsepower and torque generation | The engine is very heavy |
Smooth operations | More moving parts are there which makes manufacturing and maintenance very complex |
Conclusion
To sum up, there are two kinds of engines, namely the two-stroke and four-strokes. A two-stroke engine is where a cycle is completed in two moves of the piston and a four-stroke is where a cycle is completed in four moves of the piston. Both these engines work in operation sequence as, intake, compression, combustion and exhaust. Today, mostly a four-stroke engine is used in almost every vehicle because it is less noisy and can give higher torque and horsepower and has many advantages over two strokes.
