Engines: How It Works

Engines: How It Works


Have you ever been walking down a road, and out of nowhere you hear the screaming sound of an engine “baaaaaaahhhhh!!!!!!!!” for a split second, then a car zoomed past you at an alarming speed? 

I’m sure it left you wondering; how does it go so fast? What is responsible for hurling that huge mass of metal at that speed? How does it all happen?

Or have you ever opened the hood of a car and all you saw was a jumbled mass of metal and you wonder how all that metal manages to move the car?

Don’t worry, we’ll tell you how.

In this post, we’re gonna Hit-The-Garage and tell you about Car “Engines”

What are Engines?

Engines are machines designed to convert any form of energy; chemical (fuel), solar, electrical; into mechanical energy (motion, movement). Engines are of so many forms and sorts and operates on different principles just to achieve movement. There are steam engines, hydraulic engines, electrical engines (uses dynamos) and so on. But since we’ll be talking about cars, we’ll be talking “four stroke internal combustion engines”.

Internal Combustion

Internal combustion engines convert chemical energy (fuel) to mechanical energy (movement) through combustion (burning) inside the engine. To carry out this combustion action, a lot of engine parts come to play. Some of notable mention are:

The Cylinder

The core of the engine is the cylinder, it is the cylindrical hole inside which the piston moves up and down. The Cylinders are housed in the engine block. Single cylinder engines are typical of most lawn mowers, but usually cars have more than one cylinder (four, six and eight cylinders are common).

Spark plug

The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.


The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.


A piston is a cylindrical piece of metal that moves up and down inside the cylinder.

Piston Rings

Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:

  • They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.
  • They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.

Most cars that “burn oil” and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly. Many modern vehicles use more advance materials for piston rings. That’s one of the reasons why engines last longer and can go longer between oil changes (servicing).

Connecting rod

The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates. They are also referred to as conrod.


The crankshaft turns the piston’s up-and-down motion into circular motion just like a crank on a jack-in-the-box does.


The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).

Operation Of The Four Stroke Internal Combustion Engine

Petrol Or Gasoline Engine

This engine operates the spark-ignition system of combustion, that is, it uses spark plugs to serve as a source of fire to burn the fuel and produce motion. The processes are below outlined:


With the piston at the top of the cylinder, it begins a downward movement to the bottom of the cylinder, the intake valve of the piston then opens, allowing the piston to suck in the air and fuel mixture (the downward movement of the piston created a vacuuming effect). This stroke is the first of four stokes and is called the Intake stroke.


When the piston gets to the bottom of the cylinder, the intake valve closes, and the piston then begins to move upwards, thereby compressing the air-fuel mixture, making the air molecules close together in preparation for combustion. This stroke is called the Compression Stroke.


Just before the piston reaches the top of the cylinder, the spark plug ignites and causes an explosion of the air fuel mixture in the cylinder. During explosion, gas expands, and this causes the piston to be forced to the bottom of the cylinder. This is called the power stroke, and it is the energy source for all the four strokes


The piston then begins an upward movement towards the top of the cylinder once again, the exhaust valve opens, and then the piston forces the exhaust gases comprising; carbon monoxide, carbon dioxide, nitrogen gas, unburnt fuel, and so on; out of the cylinder into the exhaust pipe. This is the Exhaust Stroke, and the last of the four strokes.

Operation of the four stroke internal combustion engine.

The cycle then repeats itself all over again.

The four strokes are referred to as One revolution

The whole process takes place in the fraction of a second. The upward and downward movement of the piston causes the rotation of the crankshaft, and this crankshaft rotation in turn rotates the gears, which in turn rotates the tires, causing the car to zoom off.

Engine Configurations

Inline Engines

These engine sort has its cylinders arranged in a straight line. The cylinders can be three, four, five or six (this is the maximum used in commercial production). Most inline engines are four cylinders.

Working action of an inline engine

This engine type is mostly common in cars because they are small, easy to work on and can be mounted longitudinally or transversely, and are also very smooth sounding, though they usually were not really powerful, until the advent of all sorts of technologies like turbochargers, superchargers, precise timing and ignition, fuel injectors etc. Nowadays, some inline four cylinder engines are much more powerful than some V6 and V8 engines.

Toyota has the largest commercial production inline four cylinder engine measuring at 2.7litres in engine displacement.

V Engines

V engines are engines that have their cylinders arranged, as the name implies, in a V, and are merged to a single crankshaft

Most V engine have the same number of cylinders on both sides, that is, a V6 has 3 cylinders on both sides, a V8 has four, V10 has five, V12 has six, and so on.

Action of a V engine
Advantages of  V Engines

V engines are very useful because they allow for more cylinders in a small length of space; a V engine can allow for twice the number of cylinders an inline engine will use in the same length of space, they will just need a little more space on the width. They are also very powerful and fast engines. Their only drawback is that can be complex and hard to work on and have got more cylinders, hence more fuel.

Have you ever come across a vehicle that seemed to be coughing while idling, despite not being faulty? It will most likely be a V engine.

V engines are used in mostly sport cars and luxury vehicles because of the power and smooth riding, and the fact that they don’t need to achieve excessively high revolutions per minutes to produce meaningful power, though some can achieve excessively high revolutions per minute anyways.

Flat Or Boxer Engines


Boxer engines are engines that have their pistons horizontally opposed. you can call them V engines with an angle of inclination of 180 degrees. 

A flat engine at work

Due to this setup, pistons move in opposite directions and this helps to cancel out vibration, and also because of the fact that they are flat, they can be mounted lower on the vehicle giving it a lower center of gravity.

Porsche and Subaru are the leading producers of flat engines.

Diesel Engines

Nowadays, diesel engines have begun to find application in cars and pick-up trucks because they are fuel efficient and produce more power at low revolutions per minutes, though they are not speed monsters. They operate compression ignition system of combustion.

How They Work

Diesel engines have the same number of strokes and the same sequence but they do not compress air-fuel mixture, they compress only air. Air in a diesel engine is compressed more than in a petrol engine so it gets hotter than in a petrol engine.

How Diesel Engines Work

Diesel is then introduced at the peak of the compression cycle (the piston is almost at the top of the cylinder), through a fuel injector, just like a spark is introduced in the petrol engine. This diesel on contact with the hot compressed air explodes, bringing about the power stroke and the cycle then continues like in the petrol engine. The compression-ignition process is what gives all diesels their knocking sound.

Uses of Diesel engines 

Diesel engines are used in heavy duty vehicles because they are more fuel efficient (diesel doesn’t burn as fast as petrol) and are now also used in some luxury vehicles like in Audi A3, BMW 3 series diesel, Honda Civic Diesel and so on.

Now, you’ll wonder no longer and you’ll drive with full knowledge of how your engine makes your car fly!



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