This Is How Your Car's Engine Works
This Is How Your Car's Engine Works

This Is How Your Car’s Engine Works

September 18, 2020

Have you ever wondered how your car engine works? If yes, then you are in the right place. Here you will get to know what kind of magic happens under the front hood of your car. The magic of how comes down to the internal combustion engine. 

As the name suggests, Internal combustion is a combustion or burning inside a tiny enclosed space. In the IC engine, the cylinder is the tiny enclosed space in which combustion or explosion happens. Burning or combustion is a basic chemical process of releasing energy from a fuel and air mixture. 

Now one more question can enter your head, Who ignites the fuel and air mixture inside the cylinder to start combustion?

Don’t worry, we will come to this point after making a basic understanding of the air-fuel mixture. Below is the chemical reaction between fuel and oxygen which gives carbon dioxide and water vapor after combustion or exothermic reaction.

Fuel + O2 = CO2 + H20

But this is the basic chemical equation. For petrol, we need 14.7 parts by mass of air to mix with 1 part by mass of fuel to make this equation perfectly balanced, which will only produce carbon dioxide and water vapors otherwise it will produce byproducts along with carbon dioxide and water vapor.

This 14.7:1 is called the stoichiometric ratio for petrol. There are different stoichiometric ratios for different fuels for example diesel has 14.6:1, Ethanol has 8:1 and Hydrogen has 32:1.

So, Stoichiometric ratio is a ratio of fuel and air mass which completes reaction with no byproducts. 

So here is the time to discuss who ignites the air-fuel ratio. The answer depends on the type of fuel. Like if we talk about petrol then the answer is the spark plug, which gives spark to the air-fuel mixture and starts the combustion process. But in diesel engines, there is no external device used to spark the fuel. A diesel engine takes air, compresses it, and then injects fuel into the compressed air. The heat of the compressed air ignites the fuel spontaneously. A diesel engine does not contain a spark plug. Why do we use spark plug in petrol engine and why is there no requirement of the spark plug in diesel engines? This is a different topic and we will discuss this in future blogs so stay tuned with us and subscribe to our newsletter and register on the forum for future blogs. 

Now let us discuss the working of the engine-

The ignition and combustion of fuel occur within the engine and then the engine partially converts the energy from the combustion to work. Now you should have few doubts in your head like, How an engine converts energy from the combustion to work and What is work?

First, understand the assembly of the engine, Engine consists of a piston assembly that moves in a close size cylinder, and the piston is connected to the crankshaft and flywheel to convert the reciprocating motion of the piston into the rotary motion of the flywheel. The piston moves up and down in the cylinder and has two positions TDC(Top dead center) and BDC(Bottom dead center).

Now Lets put it very simply, Work is the desired output which we want from the engine like we want to drive a car from point A to Point B and, to accomplish this we need someone who can rotate the car wheel. So the engine rotates the car wheel with the help of different mechanical mechanisms. After combustion or explosion, gases push the piston down in the cylinder, which is connected to the crankshaft and flywheel.  This stroke converts energy from the combustion to mechanical work which further rotates the flywheel and the wheel of the car. 

IC engine generates power by performing 4 steps-

  1. Intake of the air-fuel mixture
  2. Compression
  3. Combustion
  4. Exhaust

This constitutes one combustion cycle.

Have you ever heard 2 stroke and 4 stroke engines? 

To understand 2 stroke and 4 stroke engines, first, we have to understand what does stroke means?

Stroke and Piston stroke is similar, and it refers to the full travel of the piston along with the cylinder, in either direction. To simply put, Piston travel between TDC and BDC is called Stoke. Single stroke means piston traveled from the TDC to BDC or vice versa.

In 2 stroke engines, the combustion cycle completes in two strokes of the piston, and in 4 stroke engines, one combustion cycle completes in 4 strokes of the piston.

If you want to read more about 2 stroke and 4 stroke engines you can check the below article-

Read more- Two Stroke & Four Stroke Engine

For more understanding let us discuss strokes of 2 and 4 stroke engines. As we discussed, 2 stroke engines completed one combustion cycle in 2 strokes which are –

  • Compression
  • Power

In 4 stroke engines, we have 4 strokes which are-

  • Intake
  • Compression,
  • Power
  • Exhaust 

All cars use a 4 stroke Internal Combustion engine unless you are driving an ancient two-stroke Saab or electric cars, your engine works on the same basic principles whether you’re wheeling a Ford or a Ferrari. Let’s take a closer look at what happens during each stroke of the piston inside the cylinder.

Intake: During the intake cycle, the intake valve opens, and the piston moves down. This begins the cycle by bringing air and gas into the engine at atmospheric temperature.

Compression: As the compression cycle begins, the piston moves up and pushes the air and gas into a smaller space. A smaller space means a more powerful explosion. Next, the spark plug creates a spark that ignites and explodes the gas(In Petrol engines).

Power: The power of the explosion forces the piston back down. This is the stroke that gets the wheels on your car rolling.

Exhaust: During the last part of the cycle, the piston goes up and the exhaust valve opens to release waste gas created by the explosion. Then these gas move to the catalytic converter, where it is cleaned, and then through the muffler before it exits the vehicle through the tailpipe.

So when you turn the key or push the start button, at the same time engine starts the combustion cycle and creates explosions hundreds of times per minute.

Do you agree ? Share your thoughts in the comments below!

Thank you!

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