Erick Ruiz has managed to make history in the world of Freestyle Motocross because he is the first American to have achieved two of the most complicated movements in this discipline, the California Roll and the Flair. However, Erick would not have been able to make such jumps if it were not thanks to his great skill for this sport and the power provided by the engine of his dirtbike.
Nowadays it is very common to hear that there are two and four-stroke motorcycles, however, only people who have previous knowledge or experience in the field really know what this means. When we refer to two and four times, really the main difference that exists between one and the other are the steps that must be done for combustion to happen and even though both engines are combustion, they work very differently.
We present the characteristics and differences between four and two stroke engines:
- The two-stroke engine performs intake, compression, combustion and exhaust with just two piston movements.
- In a two-stroke engine an explosion is generated for each turn of the crankshaft while one of four times this action happens every two turns of the crankshaft.
- When performing the four times in just two movements, the two-stroke engine offers us a greater gas mileage than a four-stroke.
- The two-stroke machine requires two lubricants, one for the inside of the engine and another for the cylinder liner. This makes it an engine that generates more smoke, because the spark plug must burn oil and gasoline, making it less environmentally friendly. Unlike the two-stroke engine, the four-stroke engine requires only one lubricant and is considerably less polluting.
- The two-stroke engine is much cheaper because it does not use valves in its mechanisms, making it also much smaller than its big brother.
- Although the two-stroke engine has a working stroke in each crankshaft, it does not have twice the power of a four-stroke engine.
- When working more times than the four-stroke engine, a two-stroke machine can present greater wear.
The 2-stroke engine
Both sides of the piston perform a function simultaneously
The crankcase must be sealed and serves as precompression chamber
engine In the 4-stroke engine only the upper face of the piston is active
The crankcase serves as a lubricant reservoir .
Gas inlet and outlet
The entry and exit of gases to the engine is done through the ports (holes located in the cylinder). This engine lacks the valves that open and close
the passage of gases in four-stroke engines. The gases enter and exit the engine through the ports (holes in the cylinder).
This engine lacks the valves that open and close the passage of gases in the four-stroke engines of the ports.
The 4-stroke valve has 2-stroke lubrication .It is done by mixing the oil with the fuel, in a proportion that varies from 2% at 5%
To better understand the difference between the 2 stroke and 4 stroke engine we will look at their advantages and disadvantages.
Advantages of a two-stroke engine
Two-stroke engines have fewer components than four-stroke engines and are therefore lighter, so it can also break or wear out less. Therefore, two-stroke are also cheaper to manufacture and repair than four-stroke, as these engines are cheap to buy.
Because two-stroke engines also have fewer moving parts such as valves or a camshaft, the moving mass is lower and speeds of 30,000 rpm and more can be achieved. Often, no transmission is necessary for remote-controlled cars with gasoline or Nitro Combustion engine to reach high speeds of about 60 – 70 km / h.
A two-stroke engine has only two strokes in contrast to the four-stroke, so and by the lower mass to be moved, the two-stroke engine can reach higher speeds faster.
Disadvantages of a two-stroke engine
The efficiency in a two-stroke compared to a four-stroke engine with the same liter of power, despite double duty cycle, mainly due to the mixing of fresh and exhaust gas in the purge of the combustion chamber only about 30% higher. In general, a two-stroke engine has an efficiency of only about 15 – 20%.
Simple two-stroke engines have a higher oil and fuel consumption due to the mixture of fresh gas and exhaust gas during combustion. That is why for a long time in cars (cars) the more economical four-stroke engine with separate oil circuit for lubrication installed.
A two-stroke engine has a high idle speed of about 3000 – 6000 U / min and hardly any torque (power) in low speeds. Therefore, the two-stroke engine is unsuitable for some RC models where much power (torque) is required, such as a remote-controlled tractor (bulldog), tanks, trucks, trail vehicles, construction machinery, etc. Especially if the model should have a reasonably realistic engine sound.
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Advantages of a four-stroke engine
A four-stroke engine has a higher torque than a two-stroke engine with the same liter power. Thus, the same torque is achieved at a much lower speed, thereby the fuel consumption and the noise is lower.
The fuel consumption is lower, as a better mixture preparation with good separation of fresh and exhaust gas through the valves is achieved. In the case of the two-stroke engine, however, exhaust gas mixes with fresh gas in the resonance tube when the fresh gas is thrown back into the combustion chamber. Thus, the efficiency of the four-stroke engine is higher and is about 20 – 30%.
Disadvantages of a four-stroke engine
The four-stroke engine has a higher total weight and has more moving mass due to more components such as the valves and camshaft. This makes him more expensive to manufacture, repair and buy than a two-stroke.
Simple four-stroke engines can only reach about half the engine speed of a two-stroke engine because four-stroke engines require more components such as the valves and the camshaft to be moved, which is only possible with very high engine speeds. In addition, a working cycle in the four-stroke engine takes twice as long as the two-stroke engine, that is, the two-stroke engine can work twice in the same time, twice.
Many remote-controlled cars with a two-stroke engine reach through the translation a speed of 60 km / h. If a four-stroke engine was installed in the same RC car, but which could reach only about 1/3 of the engine speed, a transmission would be necessary to reach the same speed of 60 km / h.