There are many differences between a 2 and a 4-stroke engine. The 2-stroke one will go through 2 stages to complete one power stroke or just one complete revolution. On the other hand, the 4-stroke engines will go through 4 different stages to complete one power stroke in 2 complete revolutions.
A 2-stroke engine can produce twice as much power as a 4-stroke and weigh less, but each type has several pros and cons. As the years passed, many things changed in the automotive industry. However, the design of these engines remained the same.
You might be familiar with some mechanical terms, but many people are still confused about the types. Below, we will discuss 2 differences between 2 and 4-stroke motors, dirt bikes, and outboard engines as well.
What is stroke in an engine?
In a motor, a stroke can be referred to as a phase of its cycle. During this phase, the piston travels from top to bottom or from bottom to top. Engines can have different phases, but 4-stroke ones have:
It is the first phase in a 4-stroke engine. The piston will move downwards, creating a partial vacuum that draws air into the combustion chamber. At the top of the cylinder, the mixture will enter through an intake valve.
In the second stage, the piston compresses the air to the top of the cylinder. As the piston moves upwards, the volume of the chamber is reduced. A spark plug ignites the mixture by the end of this phase.
It is the third phase, and it involves the expansion of the ignited mixture. It pushes the piston downwards. As a result, this force of expansion creates the engine’s power.
In the final phase of a 4-stroke motor, the piston moves upwards and squeezes all the gasses that were created during this process. An exhaust valve at the top of the cylinder will allow these gasses to exit from the chamber.
2 vs. 4-stroke engines
There are two differences between these engines. They are represented by how quickly the combustion process occurs and also by the number of processes. While one will have only two phases, the other one will go through 4 different ones. Let’s discuss thesm in more detail.
They combine the intake and compression strokes into a single one. Then they do the same with the combustion and exhaust ones. Therefore, the entire process can be completed in 2 strokes instead of 4. Every time the piston goes down, it generates power.
They can easily be identified by the exhaust header pipe, which is oversized. The specific shape and size of the expansion chamber are essential for the engine to remove burned fuel and create a vacuum for the fresh fuel and air mixture.
There are no valve openings in the cylinder head. Instead, there are several openings in the cylinder that will direct the flow of the intake charge. These openings are covered and uncovered as the piston rises and falls in the cylinder.
The processes of a 2-stroke engine are:
Intake and compression
A vacuum is created as the piston travels upward and the mixture enters the crankcase. The compression stroke happens simultaneously above the piston as it moves upward.
Combustion and exhaust
The spark plug ignites the mixture, forcing the piston down and generating power. The mixture below the piston is forced from the bottom to the top of the engine through a transfer port.
The process is similar in this type of engine, but there are 4 different phases instead of 2. They are:
Intake: The intake valve opens as the piston travels downward, drawing in the mixture.
Compression: The valves close while the piston moves upward, compressing the mixture
Combustion: The ignition system fires the spark plug while the valves remain closed. The mixture is ignited and forces the piston back down, generating power.
Exhaust: The valves open as the piston travels upward, and all the burnt mixture is expelled through the exhaust system. 4-stroke engines are usually bigger than 2-stroke ones.
Best oil for 2-stroke engines
They require special oils. If you are looking for the best one for your engine, we got you covered with 2 recommendations.
Husqvarna XP+ Oil 2.6 oz. Bottle 6-Pack
Husqvarna has engineered this oil to maximize the performance of your engine. It has been created with premium additives and semi-synthetic base oils. Husqvarna personally tested and approved this product for 2-stroke engines.
This product is also JASO-FD certified, which means that all of the oil standards are easily met and exceeded. It ensures perfect balance and engine lubricity. The low smoke formulation is designed for a low operating temperature, preventing premature engine failure.
We purchased this product and used it for our engines. What we can confirm is that Husqvarna definitely delivers all its promises. The oil formulation also contains a fuel stabilizer to help reduce the risk of failures.
Husqvarna XP Oil 12.8 oz. Bottle 6-Pack
This oil is a synthetic blend that was designed for professional usage. It can handle high loads, so you won’t have to worry about your engine failing under intense operation. Husqvarna developed one of the best oils for your 2-stroke engine with excellent lubricating properties.
It lowers the engine operating temperature and extends its life so you can enjoy your ride for a longer time. This oil includes a fuel stabilizer and produces low to medium smoke emissions. You won’t have to worry about the fumes being too much.
Best oil for 4-stroke engines
4-stroke engines will use a different oil than the 2-stroke ones. For this type, we researched and came up with the best 2 oils you can buy for your engine.
Premium Oil Formula
This oil, engineered by STP, is formulated for use in outdoor equipment. The synthetic blend is engineered with a viscosity index improver as well as anti-wear technology that will protect your engine. Along with antioxidants, this oil will help maintain the maximum performance of your 4-stroke engine.
A special formula extends the drain interval and reduces oil thickening and oxidation. It is one of the best features of this oil. You can use it for push mowers, generators, or even snow blowers with 4-stroke engines.
You can easily start the engine any time of the year, as the all-weather synthetic formula will help you regardless of the temperature. Detergents will keep the engine clean while also controlling carbon deposits.
YamaLube All Purpose Oil
The team at Yamaha developed this efficient oil suitable for motorcycles, ATVs, and scooters. A special formula protects the engine from the wear of daily use. A blend of additives and mineral-based oils will offer superior lubrication and reduce the friction between the parts.
This oil meets all safety standards and is the highest-certified engine oil regarding wet clutch performance. A genuine Yamaha product, this oil provides stable performance and strength to protect the engine from wearing too fast under intensive use.
2-stroke engines pros & cons
There are many advantages and disadvantages to 2-stroke engines. Let’s look at 4 pros and 4 cons, so you will know exactly what this type of motor offers.
High power: These engines produce a high power which is uniform in nature. The power-to-weight ratio is higher, so lighter vehicles can generate more energy.
Low maintenance: Because there is no lubrication system, maintaining it is simple. Unlike other motors, the valves do not have to be changed regularly.
Low cost: Because there is no complex mechanism, these motors are easier and cheaper to build. Usually, they are suitable for light vehicles.
Engine position: Because there are no special requirements for fuel transfer, the engine can be placed in any position. The placement is essential for modified vehicles that have been structurally changed.
Short life: Such engines will wear faster, and their average life becomes shorter. Because of the high power generated, these engines will have a short life unless a high-quality oil is used, such as those recommended above.
High pollution: These engines are unsuitable for the environment because they create more fumes. It happens because some of the burnt fuel remains inside and burns during the next cycle.
High vibrations: While enthusiasts might love the sound of such engines, the vibrations can be considered harmful. The stability of the motor is decreased, but dampeners and silencers can be used to reduce this effect.
Cooling and lubrication: The cost of cooling the engine increases because the coolant and oil are required separately. The parts need to be cooled and lubricated to prevent wear, but the lubricant can be quite expensive.
4-stroke engines pros & cons
These engines will have different advantages and disadvantages than 2-stroke ones. When you compare them, you will be able to see the difference.
Higher torque: Compared to traditional motors, the 4-stroke ones generate more power with the same amount of fuel. High torque is beneficial as the vehicle will run smoother.
Longer life: These motors have a longer lifespan because their lubrication and cooling system protect them. Wear and tear is therefore decreased, while better dampening makes them stable at higher speeds.
Fuel efficiency: The intake and exhaust are used more efficiently, and fuel loss is controlled. It leads to higher fuel efficiency, unlike 2-stroke ones that are less efficient in this aspect.
Less polluting: Because the exhaust is controlled, a fresh charge is exclusively available for combustion. Other traditional motors are not optimized in this regard and are more polluting than 4-stroke ones.
Less power: 4-stroke engines will generate less power than 2-stroke ones. It happens because there are more phases required to be completed for one rotation.
Complicated build: Many parts are involved, and the design is very complicated. Because they are difficult to construct, they are also more expensive.
Higher costs: This is one of the main disadvantages they have. Compared to the 2-stroke one, these are difficult to build and will have an increased cost.
Expensive fuels: The transport and refinement of fuels make them an expensive resource. These engines use diesel and gasoline as power resources, but one day the world will run out of these sources.
2 vs. 4-stroke dirt bike: pros & cons
In dirt bikes, the engine is significant for performance and reliability. Let’s look at some pros and cons of dirt bikes with 2 and 4-stroke engines installed.
2-stroke dirt bike
They are lightweight: Because these engines are simpler and smaller, the bikes will be lighter. A lightweight dirt bike is a significant advantage, especially in races.
They are cheaper: Compared to 4-stroke ones, the bikes with a 2-stroke engine are also cheaper. If your budget is limited, consider this point beneficial.
Increased maintenance: A simple motor makes things easier, but the lack of complexity means fewer features. You must constantly check and monitor your motor, as they can wear out quickly.
More shifting: Because they operate on just 2 strokes, you will have to shift more often as they produce more initial power.
4-stroke dirt bike
Easier to ride: These bikes are ideal for beginners or less experienced riders. They are easier to handle, and you can start on a 4-stroke one before moving to a 2-stroke dirt bike.
Less shifting: 4-stroke motors will have a wide range of speeds, making braking, shifting, and clutching easier for you. With this advantage, you can focus more on the road.
Heavier weight: They are larger, and they also weigh more. That means the entire bike will be heavier, complicating things in races or competitions.
Expensive maintenance: While it is not required often, maintenance can be quite costly for these bikes. It is because they are complex and have many components that can wear out over time.
2 vs. 4-stroke outboard: pros & cons
There are fewer moving parts in a 2-stroke motor than in a 4-stroke one. It is an important point for a boat motor. However, the former can increase pollution as well as fuel consumption.
The design of 2-stroke outboards is less complex than the 4-stroke ones. Less movement is used for the piston to open and close the intake and exhaust ports, meaning fewer parts need maintenance. These motors are smaller and lighter, which also improves their power-to-weight ratio.
They generate more power because they use 2 piston strokes to generate one full revolution. It allows for a higher speed and acceleration, which is important for competitions and races.
These motors have higher emissions, and they are not environmentally friendly. A high quantity of oil is burned with the fuel, which is then exhausted in the form of harmful emissions.
The design of this motor allows unburned fuel to exit through the exhaust port and end up in the water. This further increases the damage to the environment while also increasing fuel consumption.
These motors are highly efficient and are less costly. Experts say that 4-stroke motors are 50% better than 2-stroke ones with the same horsepower. They also produce less harmful emissions, making them almost 90% cleaner than 2-stroke ones.
All the moving parts are constantly submerged in oil. This lubrication system greatly improves the internal parts’ lifespan, making the motor highly durable and reliable.
The design makes them large and heavy, which is a compromise that limits the acceleration and top-speed performances. Because they are heavier and more complex, they also require periodic maintenance. You will need to replace the oil and filter.
2 vs. 4-stroke weed eaters
The main difference between 2 and 4-stroke weed eaters is torque. The 4-cycle one will provide more torque and be more efficient for longer projects.
A 2-cycle weed eater will operate at a higher RPM but run on more power. You should choose the one most suitable for your needs, as many models on the market are intended for different purposes.
2 vs. 4-stroke snowmobile
While they are both highly efficient and will easily plow through the snow, both of these snowmobiles work well in different situations. 2-stroke snowmobiles have a simple and basic design. It makes them generate more heat, so they need a superior cooling system.
4-stroke ones are more complex and require difficult engineering. They are also new to the market, appearing only years ago. With more parts installed, these snowmobiles are also heavier and require frequent maintenance.