Internal Combustion Engines (ICE) have faithfully served us for decades since the 19th century when Belgian engineer, Jean Joseph Etienne Lenoir, developed the ICE in 1858. The marvelous piece of machinery that rings your eardrum with its throaty bellow, waves its magic wand by mixing air and fuel, and with the presence of sufficient heat, BANG! You have combustion to get you to work, class, movies, red-light district, your GF's house and whatever places you can think of. The same 'air + fuel + heat = combustion' process applies to ICE such as petrol and diesel. However, they achieve combustion entirely in a different way which will be explained in this post.
Every car owners will be familiar with spark plug. After all, it is part of service interval to change spark plug after a certain kilometre has passed. Spark plug is responsible for providing the heat to trigger combustion on petrol engines only. Yep, only on petrol engines. What about diesel then? Well, there is no spark plug on diesel engines. Wait, how does it achieve combustion? The keyword here is pressure.
If you still recall your high school physics class, pressure is directly proportional to temperature, i.e. you increase pressure, you also increase temperature. How does that take place in diesel engines then? The air trapped inside the cylinder is squeezed at incredible pressure, twice higher than petrol engines. As a result, the air rapidly gains temperature, so hot that when diesel fuel is sprayed into the cylinder, it immediately combusts. No spark needed. This is in direct contrast to petrol where the mixture of air and fuel need to be ignited by the spark plug due to the fact that cylinder pressure on petrol engines are not sufficient enough to render spark plug unnecessary for combustion.
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