A gasoline engine, also known as a petrol engine, is the most common type of engine found in vehicles. It uses an internal combustion process involving mixing gasoline and air in cylinder chambers, then igniting it to generate energy. The gasoline engine has a four-stroke cycle: intake of air, compression of the air-fuel mixture, combustion and power stroke, and exhaust of emissions. Each stroke involves the precise opening and closing of intake and exhaust valves while the piston moves up and down in the cylinder.

1. Gasoline Engine or Petrol Engine or SI Engine
(4-stroke)
A gasoline engine is also called a petrol engine in many parts of the world. The
word “petrol” is what the British use to describe a gasoline engine. They mean
the exact same thing, which some people may not realize if they are from
America.
A gasoline engine is the most common type of engine found in the vehicles that
people drive every day. It uses an internal combustion process that involves
mixing gasoline and air together inside of cylinder chambers and then igniting
them to generate heat energy.
Four-Stroke Cycle of a Gasoline Engine
Aside from the term “gasoline engine,” another way to describe this type of
engine is by the term “four-stroke engine.” This name exists because the
gasoline engine has four different steps that it goes through for the internal
combustion process to occur.
These steps are referred to as strokes. Below are what the four strokes of a
engine entail.

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Stroke #1
The first stroke of the engine is the intake of outside air. The engine needs this
air as part of the air and fuel mixture.
The intake valve will first open to let the air inside. The piston on top of the
cylinder moves in a downward motion. This creates a force which sucks the air
into the cylinder.
Stroke #2
The second stroke is the compression of the mixture. As the air enters the
cylinder and mixes with the fuel, the force of the moving pistons causes the
mixture to compress.
Meanwhile, the exhaust valve and intake valve remain shut. It is important they
stay that way or else precious gases and liquids could escape and ruin the
entire combustion process.
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3. Stroke #3
The third stroke is the combustion itself also referred to as the power stroke.
This is where the mixture of air and fuel will actually be ignited by the generated
spark from the spark plug.
If the ignition is successful, the explosion pushes the piston down where it turns
the crankshaft.
Stroke #4
The fourth stroke pertains to the exhaust. As the fuel burns in the combustion
chamber, it generates atomized particles that are better known as exhaust
gases.
The piston pushes these emissions out of the combustion chamber through the
opening of the exhaust valve.
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