What Are the Differences Between 2-Stroke and 4-Stroke Engine

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As a car owner, you probably know some of the key features of your engine. But have you ever wondered how they work prior to the number of strokes?

Cars these days come with either 2 stroke engine or 4 stroke engines. Both their mechanism differs from one another.

In this article, I’ll discuss in depth about the mechanism of both types of engine, their differences and advantages and disadvantages.

What Is an Engine Stroke?

Before proceeding to the main part of the discussion, it’s important for you to know about engine stroke. The engines work correctly after completing the combustion process. Inside the combustion chamber, there is a connecting rod and piston that influence the process.

To burn fuel, a combustion chamber with its both connecting rod and piston need to go through 4 processes, and each process is known as stroke. For each stroke, the piston has to travel both the directions.

No matter if your car’s engine is 2 stroke or 4 stroke, it has to go through these four processes. The four processes are intake stroke, compression stroke, the combustion stroke, and exhaust stroke.

What Is a 2-Stroke Engine?

An engine that requires 2 strokes of the piston to complete one power cycle with one rotation of the crankshaft. A 2 stroke engine performs all the 4 steps of processing, but it completes in only 2 strokes. That’s why it’s referred as 2 stroke engine.

What Is a 4-Stroke Engine?

The name is telling itself why it’s called 4 stroke engine. An internal combustion engine that requires the piston to complete 4 strokes with turning the crankshaft only twice is known as 4 stroke engine. A 4 stroke engine completes all the 4 steps with 4 strokes.

Difference Between 2-Stroke and 4-Stroke Engine

To grasp the differences between these two engines, you will have to first set your perspective and viewing angle. Below, you have the dissimilarities broken down by distinct factors.

1. Numbers of Stroke to Complete a Cycle

You probably get the very first difference between these 2 type of engine. When it comes to the revolution of the crankshaft, a 2 stroke engine takes only one power stroke.

While on the other hand, a 4 stroke engine has double the numbers of stroke to complete one revolution.

An engine of a blue car

2. Producing Power

The 2 stroke engine produces power once every 2 strokes of the piston. It usually generates high torque.

In opposite, the 4 stroke engine takes 4 strokes to produce the power and generates less torque for its 2 strokes of cycle.

3. Inlet and Outlet Mechanism

There are 2 ports for fuel to get in and out in a 2 stroke engine. This port design makes its mechanism simpler.

The mechanism of 4 stroke engine is a bit complicated due to the valve that is used for the fuel to get in and out. The valve is operated through a chain and gear mechanism.

4. Flywheel Support

As a 2 stroke engine generates an even balanced force from its one revolution for only one power stroke, it requires lighter flywheel then other engines.

A 4 stroke engine produces unbalanced force because it requires one power stroke to generate two revolutions. That’s the reason why this type of engine requires heavy flywheel.

5. Burning of the Charge

The inlet port mechanism partially burns the charge and mix it with the burnt gases.

But in a 4 stroke engine, the charge is fully burned but doesn’t mix with burn gases in ideal state.

6. How the Piston Works

In a 2 stroke engine, when the piston goes for the cylinder on the top position, it forces the spark to ignite air/fuel mixture, and when it explodes, it drives the piston downward.

However, in a 4 stroke engine, when the piston is in the top to the cylinder, the spark plug burns the air/fuel and brought the piston down onto the power-stroke and makes the valve close.

7. Lubrication

Lubrication is required for a 2 stroke engine. This type of engine doesn’t have a separate chamber for oil. It mixes the gasoline with the fuel with ratios of 50:1, 32:1.

When it comes to lubricate a 4 stroke engine, the condition is complicated. This type of engine has a separate chamber and doesn’t require any mixing. Fuel doesn’t need that much of lubricating oil compared to other types of engines.

8. Thermal Efficiency

This type of engine gets hotter compared to a 4 stroke engine. Thermal efficiency isn’t that noticeable in this case.

Where a 4 stroke engine doesn’t get that hot compared to other engines and ensures thermal efficiency.

9. Weight And Power Ratio

A 2 stroke engine is comparatively lighter. That’s the reason why its power ratio is higher than its weight.

4 stroke engines are heavy that makes them having less power to their weight ratio.

A car engine

10. Fuel Efficiency And Noise

A 2 stroke engine is less efficient that makes it generating even more smoke than a 2 stroke engine. Also, it produces loud high-pitched sound.

The efficiency of a 4 stroke engine is great. That’s why this type of engine produces less smoke and make soft humming noise compared to another type of engines.

11. Weight

2 strokes engines are lighter than 4 stroke engines. While on the other hand, 4 strokes engines are heavier due to the fact that they got the heavy flywheel and also the valve mechanism.

12. Affordability

If you have less money to pay for an engine, or buy any vehicle, go for a 2 stroke engine. It is cheaper and affordable.

Due to the valve and complicated lubrication mechanism, 4 stroke engines are expansive to buy. But that won’t be an issue if you have plenty of money to spend on a vehicle.

13. Wear And Tear

Although 2 stroke engines need to be lubricated, there are more wear and tear issue with this type of engines. It’s due to the poor lubrication method.

As I have said earlier, 4 stroke engines use more complicated lubrication system, there will be less wear and tear consequences.

14. Areas of Using

2 stroke engines are mostly used in ships, motorcycles, scooter, snowmobiles, etc.

Road vehicles like cars, trucks and other modern automobiles are powered by 4 stroke engines.

Advantages of a 2-Stroke Engine

  • Inlet and outlet ports make the engine simpler.
  • Every alternate stroke acts as power-stroke which delivers more power. Also, the acceleration is significantly higher.
  • This type of engine can work in any position as the fuel works as lubrication and passes through whole cylinder and crankcase.

Disadvantages of a 2-Stroke Engine

  • For every alternate power-stroke, it needs to consume fuel. It makes the engine less fuel efficient.
  • The engine requires a mixture of both oil and air-fuel to lubricate crankshaft, cylinder walls and connecting rod. So, the oil consumption is high.
  • 2 stroke engines contribute to air pollution. The mixture of oil and air-fuel produces a lot of smoke and releases it in the air.
  • Often the fresh charge goes to undergo combustion and make its way out with the exhaust gases which leads fuel wastage.
  • Furthermore, the exhaust gases sometimes get trapped inside the chamber. It corrupts the fresh charge. Due to this improper combustion, the engine cannot deliver maximum power.

Advantages of a 4-Stroke Engine

  • Although 2 stroke engines make higher torque at higher RPM, at low RPM, 4 stroke engines make extra torque compared to 2 stroke engines.
  • As the fuel is consumed once after every 4 strokes, this type of engine is very efficient in fuel consumption.
  • There is no need to add additional oil or lubricant with the fuel, and it generates power after every 4 strokes; it makes the engine environment-friendly.
  • 4 stroke engines are durable than its competitor.
  • Except for the moving parts, you will not need to add additional oil or lubricant.

A mechanic checking a car engine

Disadvantages of a 4-Stroke Engine

  • The design and valve’s complex way of working which is controlled by chain and gear, make the engine’s mechanism more complicated. If you need to perform any troubleshoot, know that, it’s not going to be an easy task.
  • The power gets delivered after every 4 strokes making the engine less powerful.
  • A 4 stroke engine has more parts than a 2 stroke engine. It makes the engine more expensive.

Final Words

Both the 2 stroke and 4 stroke engines have their unique way of running your vehicle. If you are a type of person who needs more power and doesn’t care to spend more money on oil and lubricant and doesn’t bother about how it sounds, then you can go with a 2 stroke engine.

However, if oil efficiency, less noise, and durability is preferred to you, 4 stroke engine is your type of thing.