How a car works, from A to Z - a full explanation on exactly what occurs when you turn the ignition and put your foot on the gas.


Jan 15th, 2019

How a car works, from A to Z - a full explanation on exactly what occurs when you turn the ignition and put your foot on the gas.

So how does a vehicles wheels turn ? exactly what happens to cause so much power ? To the every day person we sit in our car, turn our key and away we go, but for those of us who feel the urge to find out exactly how and why this happens ... here it is explained in full..... how a car works, from A to Z.

For a car to work, it takes more than just pushing the start button or turning the ignition key. A car is made up of many components, some big and some small, yet the absence of an almost negligible component like a fuse in a car may stop it from working.

To fully understand how a car works, we have to start from the very beginning and shed some light on the making of a car – that is, the components of a car.

The components of a car can be grouped into three major parts, and each part plays a part in keeping the car functional. The absence of any of these components or their subsidiaries can stop the car from functioning well or even starting in the first place. These group of components includes:

Chemical Components in a Car

The chemical components of a car comprise of all chemical substances that are employed to get a car started and working. These components include the chemical compounds (aqueous acid) inside the battery of the car, the fuel (petrol or diesel) in the tank and other chemical substances that the car uses.
Without these chemical components, the car will not start.

Mechanical Components in a Car

This account for the major components of the car, from the materials that make up the engine block, to the entirety of the wheel, axles, hubs, and brakes. The mechanical parts of a car are connected in such a way that one part works the other, which means; if one mechanical component is faulty, the other parts might not function. The mechanical component of a car accounts for over 70 percent of the working parts in a car. This means that; if a car does not start or is not functioning well, the probability that the fault is mechanical is an approximate 70 percent. The components that belong to this group are:

The Engine

The engine is the core of any car. It is an intricate machine worked to transform the heat energy obtained during the combustion of gas into the power that turns the wheels of the car. The series of processes which accomplish that goal is kick-started by a spark, which touches off a blend of petrol vapor and compacted air inside the combustion chambers of the engine (the chamber is temporarily sealed during the combustion process) and makes the mixture to burn rapidly. The name internal combustion engine was coined from this chain of reaction inside the engine. The continuous combustion of the mixture of compressed air and petrol vapor leads to expansion, and in this way, power is generated to work the vehicle.

The workload on the engine of a car is massive, and so the engine must have a strong structure to be able to withstand the pressure that is placed on it. It comprises of two fundamental parts: the first is the cylinder block (this section is quite heavy and is the underlying area of the engine), and it serves as a house to the major moving components of the engine; the second is the detachable lid that serves as the head of the cylinder.
The detachable cylinder head encapsulates series of valve-controlled paths that provides passage for the combustible mixture that is designated for the cylinders. It also offers passageways for the expelled gases after combustion.

The Crankshaft is housed by the Engine block, and it transforms the repetitive movements of the pistons into circular motion at the crankshaft. Sometimes, the engine block also contains the camshaft, which works components that engage and disengage the valves that are housed in the cylinder head. In some cases, the camshaft is contained in the cylinder head joined with the pistons.

Another major component of the engine is the flywheel. It is a metallic disc that is connected to the end of the crankshaft of the engine. During ignition, this disc is worked by the pinion of the starter. It also helps in the smoothing out of pulses created by each piston in the engine block, for effective transmission of power.

A few distinctive Engine designs include;

  • In-line Engine
  • V-8 Engine
  • Horizontal-opposed Engine

The least complex and most common kind of engine is made up of four vertical barrels or cylinders laid near one another in succession. This kind of engine is referred to as an in-line engine. If the capacity of a car surpasses 2,000cc, its engine probably contains six cylinders.

In some autos, you can find the V-engines (usually the more compact kind) fitted in them, particularly in cars that have 8/12 cylinders, and a few others that have just 6 cylinders. In these cars, the cylinders are lined up in such a way that they are perpendicular to each other.

In certain engines, the angle at which the cylinders are arranged is extended to 180 degrees - this type of engine is known as the horizontally opposed engine. This type of engine is an augmentation of the V-engine, and it's quite beneficial when it comes to saving height and equalization.

The cylinders in an engine block are molded into the block, in the same way, that other auxiliary hardware mountings for auxiliary hardware like, the oil filter that provides a passageway for the oil which greases the engine, and the fuel pump. A Sump (an oil reservoir) is attached to the base of the crankcase.

The main material used in the production of the engine block is cast iron, and the head is made with the same metal. However, in some cases, aluminum is a better choice for the head since it is lighter and has the ability to dispel heat more proficiently.

Clutch System

The work of a clutch in a car is simple – it gives a command to the transmission to either engage or disengage power. The clutch of a car is linked with drive shafts, where one is the drive member, and the other is the driven member. The driving member is connected to the engine of the car, and the driven member is responsible for the provision of output power.


Different cars come with different transmissions, some manual, automatic and there is one that is not so common but has been in use for quite some time -  the CVT transmission. Regardless of which one is used by a car, the end result is the same – they facilitate gear change.

The transmission in a car is what you engage when you put a car in drive or reverse, and in automatic and CVT transmission cars the transmission varies the change of gear on its own. The transmission of a car is very vital to the movement of the car because without it the car will not leave the spot on which it is sitting.

Steering System

The entirety of the steering system contains everything that connects the steering wheel of a car to its wheels. The steering wheel is linked directly with the steering gearbox which is linked to the track rod by a Pitman arm. The track rod is then linked with the wheel of the car with a Tie rod. In most cases there is an Idler arm is also connected to the Track rod.
When the steering wheel of a car is turned, the same rotation is reflected in the wheels of the car. However, a long turn of the steering wheel may result in a small turn in the wheels of the car.

The Spark Plug

The spark plug of a car is a small component of the engine that sparks up the combustible fuel in the combustion chamber of the car. This is done by conveying the electric current from the battery or alternator of the car to the combustion site. Although diesel engines don’t require the spark from a plug to function, however, it is the serves a critical purpose in the spark-ignition engine like the four-stroke petrol engine.

Electrical components in a car

This group of components accounts for all the electrical fittings and wirings in the car. The electrical components in a car also incorporate the memory chips and the sound systems in the car. Some of the most recognized electrical components in the car are the:

Starter motor or Kick Starter

The starter motor of a car, often called kick starter is the gadget that is primarily in charge of all the process associated with starting up a car.

The vehicle starter works by taking electrical power from the car's battery. Immediately the car key is inserted and turned in the ignition of the car or When the start button is pushed, a small measure of current course into the starter relay. The kick start is made up of several components that work together to achieve the same goal: to get the car started, and these components include;

•Pinion: The Pinion is located at the head of the starter, and it is directly linked to the field wiring and the commutator. It is used for turning the flywheel of the engine during ignition
•Solenoid: The solenoid disengages the pinion of the starter when the flywheel is spinning so that the teeth of the pinion will not be damaged.
•Return spring: The return spring is directly connected to the solenoid and is linked to the pinion through the Actuating Arm. The return spring is pulled back by the solenoid when the flywheel is spinning, and the return spring pulls the Actuating arm to turn of the starter.
•Actuating Arm: The actuating arm connects the solenoid to the Pinion so that when the need comes for the solenoid to disengage the Pinion, it does so by using the Actuating Arm.
•Field winding: This is a group of wires (mostly copper) that rotates in-between two opposite magnets to generate motion when an electric current is supplied to the starter.
•Commutator and Brushes: when the Field winding moves in the magnetic field, the commutator and bushes stop it from having a torque reversal.
Generally, the starter can be found in the front of the engine of a car, however, sometimes the starter is placed at the back of the engine. When the power from the battery is not sufficient, the starter will not be able to harness enough power to start up the engine of the car. We’ll talk more about how the starter cranks up the engine later on.

The Alternator

An alternator supplies the majority of the electrical necessities of the car. An alternator is just like a phone charger – it is responsible for charging the battery of the car. It is made up of turns of the copper coil, with bipolar magnets in-between to generate current each time the shaft of the alternator turns. The electrical load of a car falls on the alternator when the car is operational, however, when the load exceeds the capacity of the alternator, the battery will have to come to its aid. The alternator is connected to the engine with the means of a pulley belt, and the tightness of this belt can affect the total output of the alternator.

The Brainbox or the Engine control unit (ECU)

It is not surprising that something as complex as a car should have a brain that would control its helm of affairs. Just like the human brain, the ECU or PCM (Powertrain Control Module) controls most of the car's functions. The brainbox of a car is a multilayer circuit board made up of electronics.

The function of the brainbox is to accept and process the various information, that is sent from the diverse sensors in your car’s engine and the other parts of your car. The brainbox of a car is a very powerful tool in the car, since it controls most of the cars function, for instance, the central locking system in your car is controlled by the ECU.

During ignition, the ECU translates information to the involved areas, where electrical current is needed, when to inject fuel and it also controls emissions that need to go out of the car.

The Battery

The battery of a car is responsible for storing electrical charge so that it can be called upon to deliver the stored electricity when the alternator is not active. A car battery supplies electrical current to the starter of the car during ignition, and when the car is running, it can supplant the alternator when the need comes. Some people might consider a car's battery to be the spine of the car, as it provides the power that is required to get it up and running. The car's battery has no tolerance for deep discharge, and its life span can be reduced by 70 percent or more if the charge on it is completely depleted. When a battery is fully charged, it can supply up to 12.6 volts.

The Fuse

All cars have classes of fuses that safeguards the electrical wiring and the electrical components in the car. Sometimes the electrical current from the alternator can surge higher than the norm, which may lead to the damage of the electrical equipment in the car. The fuses are used in the closing of the electrical circuits in the car so that when the direct current surpasses their capacity voltage, they’ll break without causing any harm to the electrical equipment.

There are four major types of automotive fuses, namely:

Blade type: This type of fuse is very common in cars, it is built with plastic, with two metallic legs that connect with the sockets. Blade type fuses come in six different sizes; Micro2, micro3, LP-mini, mini (APT or ATM), standards or regular, maxi (APX). The color code scheme for the blade type fuses represents a current rating with a color, for instance, Dark blue (0.5A), Black (1A), Gray (2A) and so on. The highest current rating for this type of fuses is Purple (120A), and it is a Maxi sized blade type fuse.

Bosch type: This type of fuse is mostly used in the old European cars, and its size is just a mere 6*25mm with pointed ends. The color code scheme for this type of fuses uses color to represent a current rating, for instance, yellow (5A), White (8A), Red (16A), Blue (25A) and Grey (40)

Lucas type: This type of fuse is mostly used in British- assembled cars, its size falls between 1 – 1.25 inch with pointed ends. The color code scheme for this type of fuses uses color to represent a current rating that varies based on three criteria, namely: continuous ampere which is equal to the rated current, instantaneous ampere, and continuous fusing ampere. For instance, the Blue color fuse can have a value of 1.5A, 3.5A, and 3A for continuous ampere, instantaneous ampere, and continuous fusing ampere respectively.

Glass-tube type: The current rating of this type of fuse depends on its length. This fuse was introduced by the SFE – Society of Fuse Engineers. This type of fuse is designed in such a way that a thread-like resistance wire is linked at both ends to metal and encased in a glass tube.

•Limiter type: This type of fuse is mostly used in electric cars.

What Happens When You Turn the Ignition Key?

At this point, it is safe to say that you now know the major components of a car and their purpose in a car. Now that we’ve gotten that out of the way, we can now go into the details of how a car works.

The operation of a car may seem like a simple process from the surface, but as you turn the ignition key of the car a lot of things happen in sequence.

We’ll be discussing all that happens when you start a car, and how the mechanical parts of the car communicate with each other to ensure a smooth ride.

The things that happen in a car from the moment your push START or turn the ignition key are vast and a little complex. However, we have broken it down into steps to give you a better understanding of how a car works.

Step 1 – The ignition key is inserted into the ignition switch
Immediately you insert your car key into the ignition switch; you have completed your first step in the process of getting your car started.
Cars that are of the past decade or two decades ago may not have security chips embedded in their ignition key, but the newer models do. You should know that one of the electrical components of the car is the brain box, and this brain box serves as the brain of the car. The brain box store information that is needed for the smooth running of your car. So when you put your key in the ignition key, the brain box is conscious of your actions and will immediately run a security check on your key. Should you use a key that is cut to look like your car key, it may not start your new model car, because it won't pass the step of the ignition process – that is the key security check.
For newer models that use keyless entry systems and a push button start, the same security check ensues. However, unlike the ignition key systems, the keyless entry cars use wireless sensors to conduct their security check on the key. Usually, when you are with the right keys, the sensor picks up the signal from the key, and by the time you push the START button, the car starts.
If your key passes the security check, and you turn the key in the ignition switch or press the start button, you move to the next step in the ignition process.

Step 2 – The starter is fed with electrical current
A brief reminder: the starter is the gadget that is primarily in charge of all the process associated with starting up a car.
When you turn the key in the ignition switch, the car through its brain box communicates this command to the starter, by supplying electrical current stored in the car’s battery to the starter.
The starter is electrically operated, so when the electric current from the battery enters into its components – the magnetic field windings, the commutators and the solenoid that controls the magnetic circuit to prevent the starter from getting damaged.
The starter requires strong electrical current from the battery to get the car started, and that is why the starter of a car is connected with thick high-resistance wire to the battery of the car. In the absence of strong electric current (if the battery is weak or without sufficient charge) the starter will not engage the engine of the car.
If the starter is fed with strong electrical current when you turn the ignition key, the starter spins its Pinion that is attached to the flywheel of the engine rapidly.
The process of turning the flywheel happens very fast, after which the starter disengages from the flywheel, and its work is done.
Immediately the flywheel starts spinning, the work of the starter is done, and another process follows.

Step 3 – Fuel is pumped into the engine
The spinning flywheel activates the fuel pump of the car. The unfiltered fuel in the car’s fuel tank is filtered by the fuel filter embedded inside the fuel tank of the car.
The filtered fuel from the fuel tank is supplied through the valve-controlled pathways in the cylinder head of the engine block to the combustion chamber in the engine block cylinders. Some cars have injectors mounted on their engine block cylinder head, and this injector controls the inflow of fuel to the combustion site. The injector also dictates the amount of fuel that goes into the engine to prevent overflow of fuel in the cylinders.
The fuel pumped into the combustion chamber of the engine block is vaporized. This vaporized petrol is also mixed with air – that is a combustible mixture of petrol and air.
When this is all done, a new process begins; the combustion process.

Step 4 – combustion takes place in the engine
During combustion, the combustible mixture inside the cylinder is burned to produce the power that turns the wheels of the car. Generally, the combustion process that takes place inside a car’s engine block follow the ensuing sequence:

The combustion process in the car’s engine begins with an intake of vaporized fuel and air. When this mixture enters into the cylinder, the pistons in the cylinders are raised to accommodate the mixture. This process is called fuel intake.
The raised pistons fall on the combustible mixtures in the cylinders, and the weight of these pistons puts pressure on the mixture.
When this happens, the combustible mixture in the cylinders are said to be compressed, and the process itself is known as compression.
Explosion and Expansion
We said we’d talk about the part that a spark plug plays in the combustion process of a car – this is it.
When the ignition key is turned, and the starter of the car has got the flywheel spinning, the spark plug conveys electrical current from the car's battery to the combustion chamber. Subsequent times the spark will take electricity from the alternator to carry on this electric current conveyance to the combustion chamber.
The Spark plug conveys this electrical current in the form of a spark to the combustion chamber, and this spark ignites the mixture in the cylinder, triggering the combustible mixture in the engine block to burn with an explosive force.
The explosion of the compressed mixture inside the combustion chamber of the engine block leads to an expansion of the hot air in the cylinder. This expansion leads to the lifting up of the pistons that compressed the mixture in the first place.
The smoke that is produced during this explosion is then let out through the outlet valve.
This is the expulsion of smoke from the combustion chamber through the outlet valve. This smoke is taken for the taken from the cylinders through the outlet valve that is usually embedded in the cylinder head of the engine block and then expelled through the exhaust pipe.
Note: the totality of the combustion process happens very fast, and the continuous repetition of the process turns the camshaft in the engine block in a rotatory motion.

Step 5 – The engine transmits power to the alternator
The continuous combustion of fuel in the cylinders of the engine brings about the rotation of the engine (crankshaft and camshaft). The camshaft and the Camshaft both have metallic discs or pulley attached to their right end, and these discs drive a belt known as the engine belt. This engine belt is connected to other components like;

  • Water Pump
  • Power Steering Pump
  • AC Compressor

The belt is linked with the pulley on the alternator so that the rotation in the engine will power it. When the pulley on the alternator rotates, the alternator produces power through electromagnetism.

Here is how it works: An alternator comprises of two parts, one is movable (the rotor), and the other is fixed (the stator). The movable part is linked directly with the alternator pulley, and fitted in such a way that it comes very close in contact with the stator, without touching it. The Stator is designed in such a way that 3 sets of wires are looped and are uniformly distributed to create a 3-phase system.

The rotor in the alternator is an electromagnet, so when it turns inside the hollow of the 3-phase system of the stator, electric current is generated.

A voltage regulator is connected to the alternator to control the outputted voltage. This connection can be done in two ways; either the voltage regulator is mounted externally on the alternator casing or inbuilt within the case.

The voltage produced by the alternator is usually between the range of 13.5 volts and 14.5 volts. Depending on the current requirements of the car, the voltage regulator can engage or shut down the charging process of the alternator. The voltage regulator accomplishes this objective by varying the applied field current of the rotor.

When the depletion of voltage goes below the 13.5 volts' mark, the voltage regulator will take it upon itself to step in to begin the charging process by applying current to the field. The reverse is the case when the voltage surpasses 14.5 V. when this happens, the voltage regulator will halt the alternator's charging process, by removing the applied current from the field. If the voltage regulator is faulty, the voltage in the alternator will surpass the max voltage, and this may cause damage to some of the equipment in the car. Although, in some cases, the fuse helps in salvaging this kind of situation so that instead of losing your gadgets you get a burnt fuse. Now you see how important a fuse is in a car.
When the engine is up and running, the alternator supplies electric current to every part in the car, and this brings to a conclusion the ignition process.
Now that the ignition process is complete and you have gotten the car up and running;

What Happens When you Decide to Move the Car?

Getting the car started is one thing, moving it brings about another series of process. Whether you plan to move it forward or you choose to put the can in reverse motion, certain things will happen before the car moves.

The process of moving a car is similar in both automatic transmission and manual transmission cars. However, the process of getting a manual car to change its position from one spot to another is much more complex on the surface compared to the automatic process.

To begin with this process, you need to start by putting your foot on the brake pedal.

Step 1 – when you put your foot on the brake pedal
In manual transmission cars, when you put your foot on the brake pedal, the result is that your car will be halted not to move on its own. However, in automatic transmission cars putting your foot on the brake pedal yields more result than just keeping your car on the spot.
In automatic transmission cars and CVT transmission cars, the simple act of putting your foot on the brake pedal sends a signal to the Powertrain Control Module (PCM) – the brainbox, that you are ready to engage the gear.
The brain box communicates this message to the sensors in the gearbox, and the gear stick frees up. In manual transmission cars, the clutch serves this purpose. However, in an automatic transmission, the clutch is often embedded in the transmission or coupled with the gearbox.
When you decide to move an automatic transmission, it is necessary to put your foot on the brake pedal otherwise you can’t engage a gear.

Step 2 – when you step on the clutch (manual transmission only)
This step is not needed in automatic or CVT transmission autos, because they don’t generally come with a clutch pedal.
The clutch pedal in manual transmission cars disengages the gear and put the car in a temporal neutral position. You cannot engage the gear in manual transmission cars without using the clutch – the clutch controls the valve in the transmission box that opens up the gear pathways when you want to engage a gear.

Step 3 – when you engage the gear
Whether you are driving an automatic transmission car, a CVT transmission car or a manual transition car, you need to put the car in gear before you can accelerate.
In automatic transmission cars, when you put your car in DRIVE, this is what happens: The torque converter pump in the automatic transmission case, gets power from the engine and this power is used to pump transmission fluid to the turbine of the torque converter. This turbine is linked with a driving shaft that is also connected to a wheel (in front wheel cars), and so the turbine turns the shaft, and the car begins to move. As you step on the accelerator, this process is repeated rapidly, and the turbine speeds up to move the car faster. As you accelerate, the gear ratio is varied by means of sensor-controlled valves in the transmission.

In the manual transmission cars, the gear arrangement is mapped out in such a way that when you shift the gear stick, the gear falls into a number (Usually from 1 to 5, some newer models have their gear numbered to 6 or 7). When you press your clutch pedal and engage gear, for instance, you put the gear in the 1 position the engine activates the torque converter pump. The turbine turns the shaft, and the car and the car now move. Although, unlike the automatic transmission cars that don't require a clutch for their gear change, in manual transmission cars you have to vary the clutch with the accelerator to get your car moving. As you reduce pressure on the clutch pedal, you increase pressure on the accelerator pedal – simultaneously. When you want to increase speed in the manual transmission cars, you have to vary the ratio of your gear by yourself, for instance, when you want to change from gear one to gear two: you must repeat the whole gear procedure, but you have to do it quickly.

When you put the car in reverse gear, the same thing happens. But, instead of a forward spin of the driving shaft by the torque converter turbine the driving shaft spins in reverse.

Step 4 – the steering wheel turns the wheels
The moment a car starts to move; a new need arises – the need to keep it on the desired path. To solve this, issue a steering wheel is used to turn the wheels of the car to a certain degree (right and left).
A quick reminder: The steering wheel is linked directly with the steering gearbox which is linked to the track rod by a Pitman arm. The track rod is then linked with the wheel of the car with a Tie rod.
Usually, the steering is preset to maintain a balanced angle that will keep the car moving on a straight path until the steering is turned towards another direction.
The wheel of a car is connected to the Tie Rod with the aid of hubs, axels and brake discs or drums. These components make the wheel turn without breaking the Tie rod.

Step 5 – when you decide to stop the car.
The wheels of your car are mostly attached to brake discs, and these discs have brake pads attached to them, to reduce speed and to completely halt the movement of the car when the need arises.
In automatic transmission cars, putting your leg on the brake pedal will signal the braking system to put pressure on the brake discs, by using the brake pads. This information is communicated by means of brake fluid.
In the manual transmission cars, you need to disable your transmission by putting your foot on the clutch before you start braking.

So this is in my masterpiece section as a lot of time and effort has gone into this article to help everyone from our young future mechanics wanting to get into the trade right up to a DIY home mechanic's, if you have any questions or have a topic in mind you would like me to write for you please feel free to drop me a email at

If you enjoyed this I think you might like my article on the history of Chrysler  or my article on the auto parts industry.