Engine Cycles

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Engine Cycles

• By Marshall gerbitz

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Introduction to Engine Cycles

• For an engine to operate, a series of events must
  occur in sequence

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Series of Events

• Fill the cylinder with a combustible mixture.
• Compress this mixture into a smaller space.

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Series of Events

• 3. Ignite the mixture and cause it to expand,
  producing power.
• 4. Remove the burned gases from the cylinder.

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Series of Events

• To produce sustained power, the engine must
  repeat this sequence over and over again.
• One complete series of these events in an engine
  is called a cycle.

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Engine Cycles

• Most engines have one of the two types of cycles
• Two-Stroke Cycle
• Four-Stroke Cycle

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Two-Stroke Cycle

• In the two-stroke cycle engine, there are two
  strokes of the piston, one up and one down,
  during each cycle.
• Then the cycle starts over again on another cycle
  of the same two strokes.
• The entire cycle occurs during one revolution of
  the crankshaft.

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Two-Stroke Cycle Engines Intake and Compression
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Two-Stroke Cycle Engines Power and Exhaust
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Two-Stroke Cycle Engine in Action
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Examples of Two-Stroke Engines

• Weed eaters
• Lawnmowers
• Chainsaws

Can you name other examples?
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Four-Stroke Cycle

• In the four-stroke cycle engine, there are four
  strokes of the piston, two up and two down,
  during each cycle.
• Then it starts over again on another cycle of the
  same four strokes.
• This cycle occurs during two revolutions of the
  crankshaft.
• Most engines today operate on the four-stroke
  cycle.

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Four Stroke Cycles
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Intake Stroke

• The intake strokes starts with the piston near
  the top and ends shortly after the bottom of its
  stroke.
• The intake valve is opened, allowing the cylinder
  to receive the fuel-air mixture as the piston
  moves down.
• The valve is then closed, sealing the cylinder.

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Compression Stroke

• The compression stroke begins with the piston at
  the bottom of the cylinder and rises up to
  compress the fuel-air mixture.
• Since the intake and exhaust valves are closed,
  there is no escape for the fuel-air mixture and
  it is compressed to a fraction of its original
  volume.

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Power Stroke

• The power stroke begins when the piston almost
  reaches the top of its stroke and the fuel-air
  mixture is ignited.
• As the mixture burns and expands, it forces the
  piston down on its power stroke.
• The valves remain closed so that all the force is
  exerted on the piston.

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Exhaust Stroke

• The exhaust stroke begins when the piston nears
  the end of its power stroke.
• The exhaust valve is opened and the piston rises,
  pushing out the burned gases.
• When the piston reaches the top, the exhaust
  valve is closed and the piston is ready for a new
  four-stroke cycle.

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Examples of Four-Stroke Cycle Engines

• Cars
• Trucks
• Tractors

Can you name other examples?
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Multiple Cylinder Engines

• Used for a more continuous flow of power.
• Modern engines use four, six, eight or more
  cylinders.
• The same four-stroke cycle occurs in each
  cylinder.

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Examples of Various Multi-Cylinder Engines
Opposing Four Cylinder Engine or Boxer Engine
Inline Four Cylinder Engine
V- 6 Engine
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Rotary Engine
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Rotary Engine
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Examples of Uses of Rotary Engines
Datsun 280Z
Mazda RX-8
Any Others?
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Any Questions