Understanding four-stroke engines

Four-stroke engines are the most common internal combustion engine used in automobiles, like trucks, cars, and some modern motorbikes (most motorbikes work with a two-stroke engine.. Four-stroke is known as the combustion cycle. It occurs during the combustion process in the internal part of an engine. A four-stroke engine transfers power stroke for every two periods of the piston or the four-piston strokes.

Check out: Understanding V8 Engine In Automobiles

Today you’ll get to know the definition, diagram, and working of four-stroke engines of both petrol (Otto cycle) and diesel types. You’ll also learn about the Otto cycle. Previously, I examined some articles on the internal combustion engine. Checkout!

Four-stroke engine


The four-stroke cycle

The following explained below is the combustion cycle of the four-stroke engine. That is, all these processes must be accomplished before a vehicle can move. these processes are:

  1. intake/inlet stroke: this is the first stage of the combustion cycle; at this stage, the piston moves downward in order to allow the fuel and air to enter the chamber.
  2. Compression stroke: at this stage, the intake valve is closed, blocking the air-fuel mixture from escaping. The piston moves up the chamber, making the air and fuel compressed. At the end of the stroke, the availability of a spark plug allows the ignition of the air-fuel mixture, providing the energy required for the combustion.
  3. Power stroke: after the combustion takes place, the heat obtained from the combusting hydrocarbon increases the pressure, giving enough energy to push down the piston and create the power output.
  4. Exhaust stroke: this is the final stage of the combustion cycle; it occurs when the piston moves back downward, and the exhaust valve opens. As the valve opens, the exhaust gas is pushed out by the piston when it moves back upwards.

Check out: V6 and V8 Engine: What is the difference and which is better

Watch the video below to learn the workings of four-stroke engines:

The thermal efficiency of an engine is the ability to convert the fuel (chemical energy) to mechanical energy. This energy will vary due to the design and model of the vehicle. Typically, gasoline engines are opportune to convert 20% of fuel (chemical energy) to mechanical energy. 15% of it is used to move the wheels, and 5% is lost to its mechanical elements and friction. 

However, the engine can be improved through thermodynamic efficiency through a higher compression ratio. The ratio is determined between the maximum and minimum volume of the engine chamber. An engine with a higher ratio will allow the fuel-air mixture to be immense, which will produce higher pressure, make the housing hotter, and increase thermal efficiency.

Check out: Diesel engines and gasoline engines: Detailed explanation

Diagram of four-stroke engines:

working diagram of four stroke engines

The Otto cycle 

Otto cycle

Nikolaus August Otto encountered the internal combustion engine built in Paris by Belgian expatriate Jean Joseph Etienne Lenoir. Lenoir successfully accomplishes the double-acting engine that works with an illuminating gas at 4% efficiency and produces only two horsepower. The illuminating gas was made from coal and developed in Paris by Philip Lebon. The engine was tested in 1861; Otto became aware of how the engine compression works on the fuel charge.

Otto decided to produce an engine to improve the poor efficiency and reliability of the Lenoir engine in 1862. He tried to create an engine that would compress the fuel mixture prior to ignition but failed as that engine would run no more than a few minutes prior to its destruction. Many other engineers tried to solve the problem, but they never succeeded.

Otto and Eugen Langen founded the first internal combustion engine production company, NA Otto and Cie (NA Otto and Company), in 1864. in that same year, Otto and Cie succeeded in creating a successful atmospheric engine. The factory ran out of space and was moved to the town of Deutz, Germany, in 1869, where the company was renamed Deutz Gasmotorenfabrik AG (The Deutz Gas Engine Manufacturing Company).

Daimler, who was a gunsmith, worked on the Lenoir engine. By 1876, Otto and Langen already succeeded in creating the first internal combustion engine that compressed the fuel mixture prior to combustion for far higher efficiency than any engine created to this time. In 1883 Daimler and Maybach left their employ at Otto and Cie and developed the first high-speed Otto engine.

They succeeded in producing the first automobile to be equipped with an Otto engine In 1885. Daimler Reitwagen used a hot-tube ignition system and the fuel known as Ligroin to become the world’s first vehicle powered by an internal combustion engine. It used a four-stroke engine based on Otto’s design. Karl Benz produced a four-stroke engine automobile that is regarded as the first car The following year.

In 1884, Otto’s company known as Gasmotorenfabrik Deutz (GFD), developed electric ignition and the carburetor. In 1890, Daimler and Maybach formed a company known as Daimler Motoren Gesellschaft, known today as Daimler-Benz.

Check out the difference between 2-stroke and 4-stroke engines

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That is all for this article, where the definition, diagram, and working of four-stroke engines are discussed. I hope you enjoyed the reading, if so, kindly share it with other students. Thanks for reading, see you next!

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