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Four-stroke engine

technology Maturity 11-13 Next article →

A four-stroke engine is a type of internal combustion engine. Internal combustion means the fuel burns inside the engine to create power. This engine design is incredibly common in modern land transport. You can find them in automobiles, trucks, and motorcycles. They also power diesel trains and light aircraft.

Ciclo del motore 4T
Ciclo del motore 4T

The engine works by moving a piston up and down inside a cylinder. This movement turns a part called a crankshaft to create mechanical work.

The engine operates through a four-step process called a cycle. Each step is known as a stroke. The first is the intake stroke, also called induction or suction. The piston moves from top dead center (T.D.C.) to bottom dead center (B.D.C.). During this stroke, the intake valve opens. The downward motion of the piston creates a partial vacuum, or negative pressure. This suction pulls an air-fuel mixture into the cylinder.

Four stroke cycle intake
Four stroke cycle intake

The second step is the compression stroke. The piston moves from B.D.C. back up to T.D.C. Both the intake and exhaust valves remain closed during this stage. This movement squeezes the air-fuel mixture tightly together. Compressing the mixture prepares it for ignition.

Four stroke cycle compression
Four stroke cycle compression

The third step is the power stroke, which is also called combustion or ignition. This happens at the start of the second revolution of the crankshaft. At T.D.C., a spark plug ignites the compressed mixture in gasoline engines. In diesel engines, the heat from high compression causes ignition. This explosion forcefully pushes the piston back down to B.D.C.

Four stroke cycle spark
Four stroke cycle spark

The final step is the exhaust stroke, or outlet. The piston returns from B.D.C. to T.D.C. once again. During this movement, the exhaust valve opens. This action expels the spent air-fuel mixture through the exhaust port.

Four stroke cycle exhaust
Four stroke cycle exhaust

After these four strokes, the cycle begins again. This continuous process allows the engine to provide steady power to a vehicle.

Engine history involves many important inventors and discoveries. In 1860, Jean Joseph Etienne Lenoir built an engine in Paris. It ran on illuminating gas and produced only 2 horsepower.

PSM V18 D500 An american internal combustion otto engine
PSM V18 D500 An american internal combustion otto engine

Nicolaus Otto studied Lenoir's engine and realized compression improved efficiency. In 1876, Otto and Eugen Langen created the first engine that compressed fuel before combustion. This was much more efficient than previous designs. Later, Gottlieb Daimler and Wilhelm Maybach developed the first high-speed Otto engine in 1883. They even built the first vehicle powered by an internal combustion engine in 1885.

4StrokeEngine Ortho 3D Small
4StrokeEngine Ortho 3D Small

There are several variations of the four-stroke cycle. James Atkinson invented the Atkinson cycle in 1882. This design focuses on efficiency rather than power density. It uses a unique crankshaft to make the power stroke longer than the compression stroke.

T cycle AtkinsonMiller
T cycle AtkinsonMiller

Modern hybrid vehicles, such as the Toyota Prius, often use this cycle.

Another major type is the diesel engine. Rudolf Diesel developed a high-compression engine in 1893. It uses heavy fuel that ignites from the heat of compression rather than a spark.

1 Audi R15
1 Audi R15

These are often used for heavy-duty tasks.

Engine performance depends on many scientific factors. The maximum power is determined by how much air the engine can ingest. Efficiency is also affected by the air-to-fuel ratio and the fuel's energy value. Engineers must manage the octane rating in gasoline engines. Octane measures how much a fuel resists self-ignition. A higher octane rating allows for higher compression ratios. This extracts more energy and prevents damage from pre-ignition.

diagrama pv de ciclo 4tempos
diagrama pv de ciclo 4tempos

In diesel engines, engineers look at the Cetane rating. This measures how easily the fuel will ignite. Understanding these principles allows engineers to build faster and more efficient machines.

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🖼️ Images & Media (13)
File:4StrokeEngine Ortho 3D Small.gif
4StrokeEngine Ortho 3D Small.gif
File:PSM V18 D500 An american internal combustion otto engine.jpg
PSM V18 D500 An american internal...
File:Prius2004.JPG
Prius2004.JPG
File:T cycle AtkinsonMiller.png
T cycle AtkinsonMiller.png
File:1 Audi R15.jpg
1 Audi R15.jpg
File:diagrama pv de ciclo 4tempos.png
diagrama pv de ciclo 4tempos.png
File:Ciclo del motore 4T.svg
Ciclo del motore 4T.svg
File:Four stroke cycle start.png
Four stroke cycle start.png
File:Four stroke cycle intake.png
Four stroke cycle intake.png
File:Four stroke cycle compression.png
Four stroke cycle compression.png
File:Four stroke cycle spark.png
Four stroke cycle spark.png
File:Four stroke cycle power.png
Four stroke cycle power.png

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