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Jan 4, 2024 | Technical Literature | 0 comments


Advanced diesel engines fuel many of the world’s most vital industries. Boats, barges, and semis move most products that consumers use every day. Agricultural equipment ensures we have the food and natural resources we need. Construction equipment powers our infrastructure.

But what exactly is a diesel engine? How does it work? And what are the primary parts and features of a diesel engine? Learn more about the basics in this blog.


Looking at the highest-level diesel engine definition, a diesel engine is a type of internal combustion engine. Internal combustion engines are heat engines that produce power through the combustion of a type of fuel and an oxidizer. In the case of a diesel engine, air and diesel fuel are compressed to produce mechanical energy.

But exactly how does a diesel engine work? It’s a fairly basic process. To begin, air is pumped into the cylinders. Then, pistons compress the air between 14 and 25 times, producing heat. Once the air is compressed, the fuel injectors spray diesel fuel into the cylinders. Introducing the diesel fuel to the hot air causes the mixture to ignite, producing chemical energy. The combustion pushes the piston back out of the cylinder, which transforms the chemical energy into mechanical energy. This process repeats hundreds to thousands of times a minute to produce enough energy to power a vehicle.


There are a number of different ways to classify diesel engines. Commonly, they are categorized by how much power they can output (small, medium, and large). However, another way to distinguish between them is by looking at the number of strokes (2-stroke engines and 4-stroke engines) used to complete an engine cycle. As you might guess, 2-stroke engines use two strokes while 4-stroke engines use four.  Let’s take a closer look at each of the two types of diesel engines:

2-Stroke Diesel Engine:

2-stroke engines provide a complete engine cycle in just two strokes. Essentially, as the cycle begins, air enters the cylinder, dispelling any old air. Then, the compression process occurs. As the piston nears the top of the cylinder, diesel fuel is added, producing chemical energy. That energy pushes the piston down, sending mechanical energy to the wheels.

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  • 4-Stroke Diesel Engine:

    In a 4-stroke engine, the pistons move up and down twice—for a total of four strokes. In addition to the compression and exhaust strokes (described above), the pistons also have return strokes. Essentially, the process begins with drawing the air into the cylinder as the piston moves down. As the piston moves up, the air is compressed. Once the piston reaches the top of the cylinder, the fuel is injected, causing the ignition. Upon ignition, the piston is pushed down, and the mechanical energy is released to the wheels. Finally, the piston moves back up to dispel the burnt gasses.

  • 4-stroke engines are the most common variety, used in most diesel trucks and automobiles.

    • Block – As the foundation of the modern diesel engine, the block is where all the parts for the basic internal combustion process are contained. The block has an open space for each cylinder, where the combustion happens.
      • Pistons – The pistons create the bottom of the combustion chamber, moving up and down in the cylinder while the engine is working. The movement of the pistons creates the compression of the air that leads to combustion.
        • Cylinder Head – The cylinder head closes the top of the open space in the block to reach the chamber where combustion happens. This head can be one unit to cover all the cylinders or multiple units that cover a section.
          • Valves – With the cylinder closed by the piston at the bottom and the cylinder head at the top, there needs to be a way to allow fresh air in and the leftover gasses out. This is where the valves come in. There are usually two valves for taking in air and two for the exhaust for each cylinder.
            • Fuel Injectors – Now, there needs to be a way to get fuel inside the cylinder, so there is something to combust. These components are a complex part of the process, spraying fuel in very precise patterns with highly controlled timing.
              • Camshaft – Rather than relying on an electrical system for opening valves and fuel injection, most engines use a mechanical process. The camshaft’s revolutions control the timing of these events by lobes on the shaft that set them into motion.
                • Connecting Rods – These pieces connect to a piston at the bottom arm and carry the force of the combustion to the crankshaft.
                  • Crankshaft – The crankshaft transfers the linear motion of combustion (the up-and-down part of the combustion process) into a rotational motion.


                  Trusted throughout the world, Cummins Inc. diesel engines are the most powerful and reliable engines. Whether you’re looking for an engine to use on the road, on the water, at the worksite, or on the farm, Cummins’ diverse line of engines has the right fit for your needs. If interested in the components of a diesel engine, don’t forget to explore key innovations that have shaped the modern diesel engine we know today.

                  If you’re looking for performance and an engine you can trust, count on Cummins. Explore the full line of diesel engines or reach out today.

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