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How Diesel Engines Work

By: Marshall Brain  | 

Diesel Improvements and Biodiesel

Cleaner fuel and stricter emissions levels should reduce the number of early deaths due todiesel engine pollution.
Cleaner fuel and stricter emissions levels should reduce the number of early deaths due todiesel engine pollution.
Photo courtesy Mario Tama/Getty Images

­During the big oil crisis in the 1970s, European car companies started advertising diesel engines for commercial use as an alternative to gasoline. Those who tried it out were a bit disappointed -- the engines were very loud, and they would arrive home to find their cars covered from front to back in black soot -- the same soo­t responsible for smog in big cities.

Over the past 30 to 40 years, however, vast improvements have been made on engine performance and fuel cleanliness. Direct injection devices are now controlled by advanced computers that monitor fuel combustion, increasing efficiency and reducing emissions. Better-refined diesel fuels such as ultra low sulfur diesel (ULSD) will lower the amount of harmful emissions and upgrading engines to make them compatible with cleaner fuel is becoming a simpler process. Other technologies such as CRT particulate filters and catalytic converters burn soot and reduce particulate matter, carbon monoxide and hydrocarbons by as much as 90 percent. [source: Diesel Technology Forum]. Continually improving standards for cleaner fuel from the European Union will also push the auto industries to work harder at lowering emissions -- by September 2009, the EU hopes to have particulate matter emissions down from 25mg/kilometer to 5mg/kilometer [source: EUROPA].

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You may have also heard of something called biodiesel. Is it the same as diesel? Biodiesel is an alternative or additive to diesel fuel that can be used in diesel engines with little to no modifications to the engines themselves. It's not made from petroleum -- instead it comes from plant oils or animal fats that have been chemically altered. (Interesting fact: Rudolf Diesel had originally considered vegetable seed oil as fuel for his invention.) Biodiesel can either be combined with regular diesel or used completely by itself. You can read more about biodiesel in How Biodiesel Works.

For more information on diesel engines and related topics, check out the links below.

Diesel Engine FAQ

Who invented the diesel engine and when?
­I­n 1878, Rudolf Diesel was attending the Polytechnic High School of Germany when he learned about the low efficiency of gasoline and steam engines. He was inspired to create an engine with a higher efficiency, and devoted much of his time to developing a "Combustion Power Engine." By 1892 Diesel had obtained a patent for what we now call the diesel engine.
How does a diesel engine work?
The diesel engine uses a four-stroke combustion cycle just like a gasoline engine. The four strokes are intake stroke, compression stroke, combustion stroke and exhaust stroke.
What happened to the inventor of the diesel engine?
Rudolf Diesel was traveling from Belgium to England on a steamship in 1913. He disappeared and his body was found floating in the water. Diesel's death was ruled a suicide, but many people believe he was actually murdered.
Is a diesel engine better?
When working on his calculations, Rudolf Diesel theorized that higher compression leads to higher efficiency and more power. He turned out to be right — a gasoline engine compresses at a ratio of 8:1 to 12:1, while a diesel engine compresses at a ratio of 14:1 to as high as 25:1.
What type of engine is a diesel engine?
Just like a gasoline engine, a diesel engine is an internal combustion engine.

Originally Published: Apr 1, 2000

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