Tuesday, 25 November 2014


I don’t have a science background. I didn’t grow up dismantling machines and getting oil all over my clothes. I grew up writing books of accounts. But life is funny sometimes and here I find myself working in the field of diesel engines and gas spare parts supply. A business that my family has run for the past 40 years.

And for a commerce student, wrapping my head around the technical details was not easy. But with proper guidance and some genuine curiosity, it can be done. For me, the curiosity came when I read a book about engines that was once owned by my grandfather, passed on to my father and then to me (much like the business itself). It was a rusty old book but it didn’t matter because the core working of an internal combustion engine has hardly changed in the past century. It got me started on the right foot, which led me to exploring other books, websites and YouTube videos about the topic.

If you’re new to this field and find things going over your head, don’t worry we’re all beginners here. First, let’s start with the basics. Just how does an engine work?

Spares involved:

-Piston (with pin and rings)
-Connecting Rod
-Cylinder Liner
-Valves and its associates like seats and spring
-Fuel Injector

When the engine runs, there are basically 4 strokes taking place (which is the reason why it’s called a 4-stroke engine).

1st stroke (Suction Stroke):

Suction air comes in the liner cylinder through inlet valve. This air pushes the piston down.

2nd Stroke (Compression Stroke):

This air is compressed as the piston comes up. Here, both intake as well as exhaust valves remain closed. At the compression stroke, the temperature of pressure air is 550 degree Celsius, which is higher than self ignition value of the diesel.

3rd Stroke (Power Stroke):

The fuel injector injects fuel in the cylinder which results in an uncontrollable fire, a spark in the cylinder which will push the piston down. This evaporates the fluid and because of the fire the temperature gets up to 2500 degree Celsius.

In the whole 4-stroke cycle, this is the only stroke where in the piston is pushed and power is generated. Hence the name, power stroke.

4th Stroke (Exhaust Stroke)

Due to inertia (the resistance of any physical object to any change in its state of motion) , the piston would move upwards again and the exhaust valves open up which would take away gas out from the cylinder.

The rotation of the valves is done in uniformity by camshaft. Depending on how the crankshaft is rotating, the camshaft will rotate at half the speed of the crankshaft to match up the rotation.

This stroke cycle is universal in any 4-stroke diesel engine, be it an automobile engine in your car or an industrial engine. The basic principle remains the same; just the number of strokes taking place at a time on the pistons would change depending on the size, nature and the application of the engine.

To understand the above explanation in animation, please refer to the YouTube links below.

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