How a Diesel Engine Works

Heavy vehicles all over the world, from 4×4’s to giant mining equipment, are powered by diesel engines. Diesels have come a long way since their invention and they now burn cleaner and more efficiently than ever. Their design makes them a good choice for lots of applications where they offer more torque and longer lifespans than petrol engines.

Diesels are a type of internal combustion engine that work by igniting a mixture of fuel and air to drive pistons up and down inside their cylinders. If you’re familiar with how the petrol engine in your car works, then you already have an idea of how a four-stroke diesel works.

Both types of engine share the same intake-compression-ignition-exhaust cycle, but diesel fuel is more energy dense and harder to ignite, so engines that use it work slightly differently:

  • Intake. On the intake stroke, each piston draws in air with no added fuel.
  • Compression. The piston compresses the air inside the cylinder, usually to a much higher compression ratio than petrol engines. A typical petrol engine might use a 10:1 compression ratio, while diesels use ratios anywhere from 14:1 to 25:1.
  • Ignition. Compressing the air creates heat. In diesel engines the air is compressed so far that it can reach temperatures over 500C. As the air in the cylinder reaches full compression, a fuel injector sprays in diesel which is instantly ignited by the heat, forcing the piston back down.
  • Exhaust. The piston cycles upwards again, driving out the burnt fuel-air mixture.

Because they don’t use spark plugs, diesel engines are very simple, but their higher compression ratios mean they need to be built tougher to handle the extra power. This is great for all sorts of vehicles because it means a properly maintained diesel should produce more power for longer.

Get in touch with us today to find out what you can do to get the longest lifespan and best performance out of your diesel equipment. Our team can answer any questions you have or book you in for the regular maintenance that will keep you running for years to come.


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