• WCS Mechanics Home
  • Mechanics 10 Home
  • Mechanics 10 Course Outline
  • Mechanics 10 Engine Page
  • Mechanics 10 PowerPoints
  • Mechanics 10 Practice Quizzes
  • Mech 10 Booklets
  • Mechanics 20A Home
  • Mech 20 Booklets
  • Mechanics 20A Course Outline
  • Mechanics 20B Home
  • Mechanics 20B Course Outline
  • Mechanics 20A Practice Quizzes
  • Mechanics 30A Home
  • Mechanics 30A Course Outline
  • Mech 30 Booklets
  • Mechanics 30B Course Outline
  • Mechanics 30B Home
  • Mechanics 30 PowerPoints
  • Mechanics 30 Quizzes
  • WCS Mechanics Blog
  • Demonstration Videos
WCS Automotive Mechanics

Internal Combustion

Picture

   Almost all cars currently use what is called a four-stroke combustion cycle
to convert gasoline into motion. The four-stroke approach is also known as the
Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes
are illustrated below. They are: 

  •     Intake stroke

  •     Compression stroke

  •     Combustion stroke

  •     Exhaust stroke

Picture

  1. The piston starts at the top, the intake valve opens, and the piston moves
    down to let the engine take in a cylinder-full of air and gasoline. This is the
    intake stroke. Only the tiniest drop of gasoline needs to be
    mixed into the air for this to work.

  2. Then the piston moves back up to compress this fuel/air mixture.
    Compression makes the explosion more powerful.

  3. When the piston reaches the top of its stroke, the spark plug emits a spark
    to ignite the gasoline. The gasoline charge in the cylinder
    explodes, driving the piston down.

  4. Once the piston hits the bottom of its stroke, the exhaust
    valve opens and the exhaust leaves the cylinder to go out the tail
    pipe.

  5. Notice that the motion that comes out of an internal combustion engine is
    rotational, while the motion produced by a potato cannon is
    linear (straight line). In an engine the linear motion of the
    pistons is converted into rotational motion by the crank shaft. The rotational
    motion is nice because we plan to turn (rotate) the car's wheels with it
    anyway.

Home
Engine Basics
Mech 10 Home