Advantages and disadvantages of the two-stroke engine

Due to anti-pollution regulations, vehicles with two-stroke engine down the roads. It has been many years since there have been cars with this type of engine. However, we can still find some small displacement motorcycles with this type of propeller.

Like the four-stroke engine, the two-stroke engine has a four-phase cycle. However, it is characterized by perform all four in just two counts. The phases of admission, compression, expansion and exhaust are grouped in the times of admission-compression y expansion-exhaust.

Parts of a two-stroke engine

A two-stroke engine is much simpler than a four-stroke engine. Mainly because, instead of valves, it has three lights, which is where the air-fuel mixture enters and also where the lubrication takes place. It is the piston itself that locks or unlocks them simply with its position.

Engine block: where the holes or cylinders that make up the walls and top of combustion chambers. It also has the louvers:
- Intake port: where the mixture is allowed to enter the crankcase
- Charge port: through which the mixture that is in the crankcase passes into the combustion chamber
- Exhaust port: through which the exhaust gases are expelled once the mixture has been burned
Intake manifold: ducts through which air enters in the combustion chambers, when the position of the piston allows it.
Manifold: ducts through which the exhaust gases exit, when the position of the piston allows it.
Pistons: Are the moving parts that close the combustion chambers below. They are attached to the crankshaft by connecting rods.
Crankshaft: axis that transform linear motion rise and fall of the pistons in circular motion.
Cranks: moving parts that attach the pistons to the crankshaft.
Plugs: in two-stroke engines it is required some spark plugs that cause a spark to detonate the mixture.
Carter: It is the part that shut the engine down, but unlike in four-stroke engines, it does not contain the lubricating oil. In two-stroke engines the oil is mixed with air and fuel. Therefore, instead of being bucket-shaped, it is usually semi-cylindrical in shape to leave just enough space for the crankshaft.

Two-stroke engine operation

Before describing what the theoretical cycle of a two-stroke engine is like, it is worth explaining two peculiarities:

An explosion occurs at each revolution of the crankshaft.. That is to say, twice as much as in four-stroke engines, which make two revolutions for each explosion.
The crankcase performs two functions: on the one hand, it is a precompression chamber of the mixture of air, fuel and oil. On the other hand, this mixture, which contains between 2% and 5% oil, is what lubricates both the cylinders, the crankshaft and the connecting rods.

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The theoretical cycle of a two-stroke engine is:

Admission-compression: when the piston reaches the bottom of its stroke, it uncovers the charging port and allows the mixture in the crankcase to enter the combustion chamber. The piston then moves up to compress this mixture, but at the same time creates a negative pressure in the crankcase so that it fills back up with more mixture through the intake port.
expansion-exhaust: When the piston is at its top dead center, the spark plug generates a spark that detonates the mixture. This pushes the piston down again to gain kinetic energy. A movement that at the same time compresses the mixture that is in the crankcase. When lowering the piston, it uncovers the exhaust port so that the gases can escape. Going down more, it uncovers the charge port and we return to the admission-compression time. This mixture input helps to get out the gases that remain in the combustion chamber.