How Does a Diesel Engine Work?

Diesel engines used to only be found in large trucks and foreign cars, but more cars and smaller trucks are running on diesel engines.  Diesel engines are more efficient than gasoline engines, which offsets the slightly higher price of fuel.  

• Diesel engines were made to be more efficient than gasoline engines, but they are loud and do not burn as clean as gasoline.  Technology advances have made the engines burn cleaner, but the public still did not see a need for a diesel engine in the family car.  As engines have become quieter and cleaner, we are seeing the need for more energy efficient vehicles, so diesel engines are becoming more popular in the United States.


• Diesel fuel is heavier than gasoline, so it does not vaporize as easily as gasoline.  Gasoline motors ignite the fuel with a spark plug, but diesel will not ignite with a spark.  Instead, a diesel engine uses a high compression ratio to heat the air.  Diesel fuel is injected into the hot air, and it ignites spontaneously.


• Air in the combustion chamber is compressed at a ratio of 15:1 to 22:1.  This brings the air to 1,022 degrees Fahrenheit within the chamber, and diesel is injected directly into this chamber.  The extreme heat vaporizes the diesel, and the vapor is ignited by the heat.  It does not need a spark like gasoline does.  After the vapor is heated and ignited, droplets of diesel continue this cycle of vaporizing and burning and the droplets get smaller and smaller until they are burnt off.  The piston is thrust downward due to the expansion of the diesel, and this is what powers the crankshaft.