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:

  • The intake stroke.
  • The compression stroke.
  • The combustion stroke
  • The exhaust stroke.

The piston is connected to the crank shaft by a connecting rod Here's what happens as the engine goes through its cycle:

  • 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. (Part 1 of the figure) This is the intake stroke . Only the tiniest drop of gasoline needs to be mixed into the air for this to work.
  • Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. (Part 2 of the figure)
  • 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. (Part 3 of the figure)
  • 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. (Part 4 of the figure)

Now the engine is ready for the next cycle, so it intakes another charge of air and gas.

Notice that the motion that comes out of an internal combustion engine is rotational .  In the engine the linear motion 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.

Two other things that are good to note:

  • There are different kinds of internal combustion engines. The gas turbine is another form of internal combustion engine. A gas turbine engine has interesting advantages and disadvantages, but its main disadvantage right now is an extremely high manufacturing cost (which means it costs more than the piston engine used in cars today)

  • There is such a thing as an external combustion engine. A steam engine in old-fashioned trains and steam boats is the best example of an external combustion engine. The fuel (coal, wood, oil, whatever) in a steam engine burns outside the engine to create steam, and the steam creates motion inside the engine. It turns out internal combustion is a lot more efficient (takes less fuel per mile) than external combustion, plus an internal combustion engine is a lot smaller than an equivalent external combustion engine. This explains why we don't see any cars from Ford and GM using steam engines.
Almost all cars today use a reciprocating internal combustion engine because this engine is:
  • relatively efficient (compared to an external combustion engine)
  • relatively inexpensive (compared to a gas turbine)
  • relatively easy to refuel (compared to an electric car)
These advantages beat any other existing technology for moving a car around, and Neco beats anyone for warranty, service and quality on replacement internal combustion engines. That's why more people turn to Neco across the U.S. each year to give their vehicles thousands of extra miles of useful life.

 

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