Diesel engine principles are pretty straightforward for the experienced mechanic but what about routine everyday people who have never taken the time to discover more about a diesel engine and how it works?
In this short article, we are going to describe in layman’s terms the basic principles of a diesel engine. Let’s begin, shall we?
What’s the difference between the petrol engine and a diesel engine?
The first thing you should know is a petrol engine and a diesel engine are absolutely different. A Petrol engine is built much lighter than the much heavier constructed diesel engine and runs on an air/fuel mixture integrated with a high energy spark that is timed to ignite the air/fuel mixture inside each engine cylinder at the precise time developing power and torque [turning force] which drives your vehicle.
A diesel engine uses high compression [intake air that is compressed/squished] into an extremely little space inside each cylinder causing severe heat! This is called ‘Heat of Compression’ which sparks an extremely great high-pressure mist of diesel fuel that is injected into the cylinder at the exact time.
So you now know that a gpetrol engine needs a high energy spark to run while a diesel uses ‘Heat of Compression’
The four-stroke principle
Every engine today runs on four strokes or four cycles- both these terms mean the exact same. Here is how the four-stroke diesel engine operates.
1. Intake Stroke:
Intake valves in the cylinder head open permitting pressurized air to enter each cylinder while the piston is traveling downward.the the pressurized air supply is enabled by the TURBOCHARGER which pushes air into the intake system offering the diesel engine an increase of air to keep up with an instant injection of fuel
2. Compression Stroke:
When the piston starts to make its way back upward the valves close which traps the intake air in the cylinder which permits compression to occur, the HEAT OF COMPRESSION is reached when the piston reaches the top of the cylinder, the diesel fuel is then injected into the cylinder at the precise time.
3. Power Stroke:
After injection takes place an explosion occurs in the cylinder because of the combination of heat and atomized diesel fuel. This causes the piston to be forced downward which produces torque and the horsepower needed from a common diesel engine.
4. Exhaust Stroke:
After the power stroke, the piston moves upward once again while the exhaust valves open permitting the previously ignited gases to escape to the environment out the exhaust system.
As discussed before, each cylinder goes through this specific series over and over in a set firing order. For instance, a 6 cylinder diesel engine has a firing order of 1- 5- 3- 6- 2- 4 which is the order that each cylinder goes through, following the 4 strokes discussed above. This series has been crafted to allow the diesel engine to run efficiently with no imbalance.
There is much to find out about diesel engines and a ton of info online. If you have ever thought about buying a car with a diesel engine you have made a prudent decision! The extra cost will be to your advantage, so it is recommended that you discover more about diesel motors before you choose which one to select.

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