Even with all the changes and new car design ideas, one thing has stayed the same: how two-stroke and four-stroke engines are made. You may have heard of these engines before, but you may wonder what makes them different. Here’s what you require to understand how well each engine works and how to maintain it in good shape.
What makes a 2-stroke engine different from a 4-stroke engine?
A 4-stroke engine requires four steps, or two entire revolutions, to accomplish one power stroke, whereas a 2-stroke engine only requires two stages, or one complete rotation, to produce one power stroke. This means that a 2-stroke engine could have twice the power of a 4-stroke engine while also being lighter.
Four-stroke engines use less fuel and are better for the environment. In four steps, they work:
- Intake: The intake tap is open, and fuel comes in when the piston moves down.
- Compression: The fuel is pushed together as the piston gets up.
- Power: The engine’s power comes from lighting the fuel after it has been compressed.
- Exhaust: When the exhaust valve is open, gases leave the cylinder.
The compression and ignition steps are done together on the upstroke of a two-stroke engine. On the downstroke, the power and exhaust steps are done together. This method has fewer moving parts, which makes it easier to keep up, but it produces less torque.
The two steps include:
- Upstroke (ignition/compression): The piston keeps rising, and air and fuel enter the crankcase. The fuel-air combination is squished together and set on fire.
- Downstroke (power/exhaust): Once fuel is lit, the piston is forced down, and the exhaust comes out.
Both engines have pros and cons, and which will work best for you rely on your needs. Even though 4-stroke engines work well and last longer than 2-stroke engines, 2-stroke engines are more delicate and go faster.
2-Stroke and 4-Stroke Engines: A Comparison
The main variance between two-stroke and four-stroke engines is how they work. Both engines get their power from the combustion cycle. The primary variance between a 4-stroke and a 2-stroke is that a 4-stroke engine has four stages, or two full revolutions, for each power stroke. One power stroke on a 2-stroke engine comprises two stages or one full rotation.
During the combustion cycle of an engine, the piston moves upward and downward in a cylinder. When the movement of the piston from the middle of the top of the cylinder to the bottom, this is called a stroke. During a burning process, the piston takes the air and gas as it moves down the cylinder. As the piston moves back to the top, the intake valve opens to let the exhaust out.
Two-stroke engines work because the piston does more than one thing when it moves up and down. When the piston moves up, it compresses the mixture of air, fuel, and oil in the combustion process, and when it moves down, it draws in a new mixture of air, fuel, and oil from the crankcase.
Two-Stroke and Four-Stroke Engine Power Cycle
A very common type of internal combustion engine runs on four strokes. Each power cycle in an engine is made up of four things that the pistons do. A piston moving up or down is what is meant by an event. When all four things happen, the cycle is done and ready to start over.
Even though the combustion cycle is pretty much the same for both engines, the number of revolutions the piston must move to finish the process is different. The five steps of the combustion cycle (intake, ignition, combustion, compression, and exhaust) are done in two piston strokes in a two-stroke engine.
A four-stroke engine, on either hand, needs four strokes of the piston to finish a combustion cycle. For a two-stroke engine, this process can be thought of as one crankshaft turn, and for a four-stroke engine, it can be thought of as two crankshaft turns.
Pros of a Two-Stroke Engine
- A two-stroke engine weighs less and takes up less space than a four-stroke engine.
- Since one power stroke is needed for each crankshaft turn, the engine’s turning motion is even.
- The lack of valves makes the design of this engine simple.
- When this engine runs, there is less friction between the parts, so it works better.
- This engine has a high power-to-weight ratio and a big boost in power.
- The engine can work when it is hot or cold outside.
- The engine has ports for both air and exhaust.
Cons of a Two-Stroke Engine
- Two-stroke engines use more gas because only a small amount of the new fuel mixes with the exhaust gases.
- During the operation, you may hear a lot of shaking or noise.
- This engine won’t last as long because it wears out more quickly.
- A two-stroke engine has a small range of speeds where it works best. This is called the power band.
- While the engine is idling, this type could become unstable.
- You might have trouble with this engine when you try to scavenge.
- A two-stroke engine doesn’t burn as cleanly as a four-stroke engine, so it puts more pollution into the air.
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Uses of a Two-Stroke Engine
A two-stroke engine can be used for many different things. The two-stroke motor is used in tools like chainsaws, blowers, trimmers, and hedge trimmers used outside. A two-stroke engine can also be found in outboard motors, motorcycles, and dirt bikes used for transportation and work.
Pros of Four-Stroke Engines
- When running, four-stroke engines produce more torque at a lower RPM.
- A four-stroke engine uses fuel only once every four strokes, which makes it a more fuel-efficient choice.
- Four-stroke engines pollute less because the fuel doesn’t need to be mixed with oil or lubricant.
- These engines are strong and can handle more wear and tear than others.
- With a four-stroke engine, you won’t need any extra oil.
- When running, a four-stroke engine makes less noise and vibration than a two-stroke engine.
Cons of Four-Stroke Engines
- The four-stroke engines are heavier than their two-stroke counterparts because they have more parts.
- A four-stroke engine has more parts and valves, which makes it more expensive to fix and maintain.
- This engine is less powerful than a similar two-stroke engine because it only gets power once every four times the piston turns.
- This engine is made with a gear and chain system, which can make it hard to keep up and fix.
- A four-stroke engine must be maintained often, which drives the price of goods and services.
Uses of a Four-Stroke Engine
Four-stroke engines are great for many things, like vehicles and outdoor power tools. A lawnmower is one of the most common gear pieces with a four-stroke engine. You can find these engines in everything from a 7cc radio-controlled car engine to a Cat C18 diesel motor engine with about 800 horsepower.