Ever pop the hood of your car and wonder what’s going on?  In today’s post let’s learn about your car’s engine.

Currently, the fastest way to high performance and fuel efficiency is to use the internal combustion engine.  The combustion (explosion) occurs inside the engine, and the energy is used to propel the vehicle forward.  The internal combustion engine has many forms, such as, diesels, gas turbine, two-stroke and Hemi engines are all part of the family.

On the other hand, there is an external combustion engine. In an external combustion engine, the energy (fuel) is burned outside the engine.  This energy propels the vehicle forward.  The best example of this would be a steam engine on an old-fashioned car or train.

Most cars use the four-stroke combustion cycle.  This converts gasoline to movement.  The four strokes are:

1. Intake stroke.  The piston is at the top and moves downward.  When it is halfway down, the intake valve opens and fuel and air come in and mix in the cylinder.

2. Compression stroke. Compression (or squishing) of the fuel/air mixture by the piston.  The molecules are being crushed as the piston moves up in the cylinder.  All the valves are closed.

3. Combustion stroke.  Here comes the job of the spark plug.  The spark plug emits a spark (sent from the distributor via the electrical system) and ignites the fuel (air/gas mixture).  The resulting explosion drives the piston down.

4. Exhaust stroke. When the piston is at the bottom of it’s up/down stroke, then the exhaust valve opens and as the piston moves up, it pushes the waste gasses (CO 2 and NO 2) out the exhaust system and polluting our beautiful atmosphere.  Now the vales are all closed.  Trivia: NO 2 is nitrous oxide and is used for giving race cars a quick boost of speed.  Mostly used for dragsters.

Now the cylinder is ready to repeat the intake stroke and start all over again.  Diesel engines are different because they don’t have spark plugs.  I’ll explain that another time, so stay tuned!

6 thoughts on “How a Car Engine Works

  1. Finally a post my girls can relate to! 4 strokes for power – breast stroke, back stroke, butterfly and freestyle!
    Cynthia

  2. Candler –

    Thanks for the clear and concise explanation. I always wondered what the heck was going on under my hood !

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