Product Manual

Internal combustion engines were invented in the
1860s, but it was the German engineer Nikolaus
August Otto who in 1867 patented the four-stroke
“Otto” cycle engine that we use today.
Internal combustion engines are gen-
erally twice as efficient as “external
combustion” engines, like the old
steam engines.
The power of an internal
combustion engine comes from
carefully controlled burning of
fuel inside the cylinder.
HOW A GAS ENGINE WORKS
THE FOUR CYCLES
Image Copyright: tsuneo
Internal
Combustion
Engine
Motor-Works
™
The four cycles – or “strokes” – of an engine are “Intake”, “Compression”, “Power” and “Exhaust”. These repeat again and
again in the same order as the piston moves up and down in the cylinder. Since most engines have more than one cylinder, these
cycles are alternated in the different cylinders to reduce vibration and make the engine run smoother.
In the Intake stroke, the piston is descending and the Intake Valve
is open. Since the piston is tightly sealed against the walls of the
cylinder, it pulls the gas/air mixture into the cylinder behind it.
In the Compression stroke, the piston has gone down as far as it
can and is now moving back up. Both valves are closed, so the
gas has no place to
go and is “compressed” by the piston.
COMPRESSION
In the Power stroke, the piston has just reached the highest point
it can travel when the spark plug ignites the fuel. The gas literally
explodes and pushes the piston rapidly down. This provides the
engine’s power.
In the Exhaust stroke, the piston has again gone as far down as it can
and is now moving back up. The exhaust valve is open and the piston
pushes the “exhaust” gases out of the cylinder as it rises. As soon as the
piston reaches the top of the cylinder, the exhaust valve closes, the
intake valve opens and the cycles begin again.
2
POWER
3
EXHAUST
4
INTAKE
1
© 2015 Smithsonian Institution
®
. NSI International, Inc., New York, NY 10010
Spark Plug
Piston
Piston
Rod
Cylinder
Oil
Crankshaft
Exhaust Valve
Combustion
Chamber
Intake Valve
INTERNAL COMBUSTION
The Motor-Works model shows the basic parts of a
four cycle internal combustion gasoline engine. This
is the most common type
of gasoline engine and is
the kind used in most
cars and trucks.
The power of an internal
combustion engine comes
from the carefully controlled
burning of fuel inside the
cylinder. That’s why it’s called
an “internal combustion”
engine – it literally means
“burning inside.” Internal
combustion engines are
generally about twice
as efficient as “external
combustion” engines, like
the old steam engines.
Internal combustion engines
were invented in the
1860s, but it was the
German engineer Nikolaus
August Otto who in 1867
patented the four-stroke
“Otto” cycle engine that
we use today. This is the
kind of engine shown in
the Motor-Works model.
All “four-stroke” engines
work in the same way
and have the same basic
parts inside. These are
shown in the drawing.
Understanding how these parts work will let you
understand the basic principles of all engines.
To begin
with, gasoline
mixed with air is burned
in the Combustion
Chamber above the
Piston. The gas/air
mixture comes into the
chamber through the
Intake Valve and is
ignited by a spark from
the Spark Plug. The
waste gases that remain
after the gasoline burns
are pushed out of the
engine through the
Exhaust Valve. The
round Piston that moves
up and down in the
Cylinder is connected to
the Crankshaft by the
Piston Rod. As the
piston moves up and
down, the “rod” turns
the Crankshaft and
changes the up/down
motion of the piston into
rotary power.
49013 : sms Motor-Works Poster Front Size: 22.8”(W) x 34.6”(H) 5 Colors : CMYK, PMS 877C Metallic Spot Color
4-April-2015