How Does a Car Work?

Cars have been around for over a century, so it’s easy to take them for granted. You hop into the driver’s seat, turn the key (or push the button), and off you go. Simple, right? Well, there’s a lot going on under the bonnet.

Behind the comfort and ease of modern vehicles are many complex systems and impressive feats of engineering. This guide will take you through the essential components that power, steer and stop your car, so you can better understand what keeps you moving.

How does a car engine work?

An engine works by converting fuel into energy through a process called combustion. This energy is then used to power the vehicle.

Here’s a simple breakdown:

• A small amount of fuel mixes with air in the cylinder.

• The spark plugs (or glow plugs in diesel engines) help the mixture ignite, creating an explosion.

• The explosion pushes the piston, which moves up and down.

• This motion turns the crankshaft, which eventually drives the car’s wheels through a system of gears.

Most modern cars have four-cylinder engines, but larger vehicles may have six or even eight cylinders for added power.

Read this guide to learn how an engine works in detail.

Next, let’s take a closer look at the different parts of an engine and what they do.

Engine timing

The timing system ensures that the crankshaft (which moves the pistons) and the camshaft (which opens and closes the valves) stay synchronised.

If the timing isn’t controlled, the valves and pistons could come into contact with each other, causing severe damage. 

There are three types of timing mechanisms:

• Timing belts (cambelts) – Rubber belts with teeth that grip gears.

• Timing chains – Made of metal, more durable, and oil-lubricated.

• Wet belts – A belt located inside the engine with oil for lubrication.

Check out the following guides to learn more about engine timing:

• What Is a Wet Belt?

• How to Find Out if Your Car Has a Timing Chain or Timing Belt

Ignition system

Whether a car runs on petrol or diesel, there has to be a way of igniting the fuel to generate the power required for movement. 

• Spark plugs are used in petrol engines. They provide the spark required to start the combustion process and operate continuously while the car runs.

• Glow plugs are used in diesel engines. They heat up at one end to encourage efficient combustion when the vehicle starts.

Curious about the difference? Learn more in our spark plugs vs. glow plugs guide.

Turbocharging

Some cars are fitted with a turbocharger, which forces more air into the engine. More fuel is added correspondingly to increase the strength of the combustion, ultimately leading to more engine power.

A turbo doesn’t require additional power to turn as exhaust gases drive the turbine, and it only activates above certain speeds, allowing for better fuel efficiency.

This guide explains how a turbo works in detail.

How does a car transmission work?

The transmission is another name for the gearbox. It delivers power from the engine to the wheels to move your car. This section of the guide focuses on the transmission and its closely related components, the flywheel and clutch.

How does a gearbox work?

There are a few different types of gearboxes. Here, we will focus on the operation of a standard manual transmission.

• Power is sent through a shaft connecting the engine and gearbox.

• The gearbox uses this power to turn a series of other shafts with gears fitted to them.

• When the driver presses the clutch pedal, the clutch disconnects the gearbox from the engine to enable a gear change.

• A selector fork within the gearbox uses a synchroniser to engage the gear the driver selects.

• Releasing the clutch pedal allows the clutch assembly to reconnect the engine’s power to the gearbox smoothly.

• Once the gear is engaged, the gearbox directs power from the engine to the wheels again.

Check out these guides to learn more:

• How does a gearbox work?

• What is a DSG gearbox?

How does a clutch work?

The clutch is responsible for engaging and disengaging the power transmitted from the engine to the gearbox. It allows your car to run more smoothly while you change gear.

Here’s a quick outline of how it works:

• The driver pushes the clutch pedal, activating the release mechanism that causes the clutch to disengage.

• The connection between the engine and transmission (gearbox) is temporarily broken, allowing the engine to spin independently.

• The driver can select a new gear without damaging the gearbox.

• When the driver releases the clutch pedal, the pressure plate applies force to the clutch disc, pressing it against the flywheel.

• The friction between the flywheel and clutch disc is crucial for a smooth engagement.

• The connection between the engine and transmission is reestablished.

Learn more about how a car clutch works here.

Flywheel & torque converter

Some cars have a flywheel; others have a torque converter.

The flywheel is located between the clutch and the engine. Its purpose is to make driving smoother by balancing out the up-and-down motion of the engine’s pistons. It stores rotational energy as it spins, keeping the car moving or idling without the engine stalling.

Most modern combustion engine cars are fitted with a dual-mass flywheel, but you can get single-mass flywheels too. This guide explains everything you need to know about flywheels.

How does a car’s steering & suspension work?

Steering and suspension are two closely related systems.

Steering

Rack and pinion is the most popular type of steering system. It converts the rotational motion of the steering wheel into the linear motion that turns the wheels using a circular gear (the steering pinion) with teeth that lock on a bar (the rack).

Modern cars usually have power-assisted steering, which uses an engine-driven pump or electric motor to make it easier for you to turn the wheel.

Want to learn more about car steering systems? Check out this guide.

Suspension

Suspension connects your car to its wheels, providing stable handling and a smooth ride by absorbing bumps in the road. It works by maximising the friction between the wheels and the road surface. 

Suspension systems consist of several parts:

• Coil springs

• Shock absorbers - learn more

• Struts 

• Rods

• Linkages

• Bushes - learn more

Learn about different suspension systems and how they work.

How does a car's cooling system work?

The car's cooling system works by circulating coolant around the engine and radiator.

• When you first start your car, the coolant stays in the engine to help it get up to temperature.

• Once the coolant reaches the right temperature, a thermostatic valve opens, allowing it to flow into the radiator.

• Air from the front grille flows over the radiator, creating a cooling effect, which allows the coolant to lose heat as it travels from the top of the radiator to the bottom.

• The water pump moves the coolant from the radiator to the engine again.

Learn more about how a cooling system works here.

Wheels & tyres

Wheels and tyres are the unsung heroes of your car, often forgotten in favour of the exciting power of the engine or the sleek design of the bodywork.

Wheels are metal or alloy rims that support the tyres, providing structural integrity, whereas tyres are rubber or composite parts that cover the wheels, delivering traction, cushioning and grip. They must have the correct tread depth and grip to work effectively.

Take a look at the following guides if you want to know more:

• Ultimate car tyres guide

• What is a locking wheel nut?

How do car brakes work?

We’ve established how a car’s power is created and the parts that allow it to move. But how does it stop? That’s where the braking system comes in.

Most modern cars have hydraulic brakes, so you don’t have to push the brake pedal as hard - the fluid does some of the work for you. 

• You press the brake pedal.

• The hydraulic unit sends brake fluid through the brake hoses into the calliper.

• The fluid places pressure on the calliper piston, forcing the calliper to squeeze the brake pads onto the brake discs.

• The friction between the pads and discs slows the vehicle.

Read this guide for a detailed explanation of how brakes work.

Electrical parts & sensors

How does a car battery work?

Car batteries use electrochemical reactions to create electricity. There are two types of plate inside the battery - negative and positive, made of lead dioxide and lead, respectively - immersed in an electrolyte solution of sulphuric acid and water.

An electrochemical reaction occurs when the battery is connected to the starter motor, creating an electric current that flows through the battery terminals and cables. This current provides the power to start the engine and run various electrical systems.

Check out our guide to car batteries to learn more.

How does an alternator work?

The alternator turns mechanical energy into electrical energy to feed the car’s electrical systems and charge the battery.

• A pulley turns the alternator’s rotor shaft, which spins magnets inside a coil. 

• The spinning magnets create an alternating current (AC) of electricity in the stator. 

• The current is channelled into the alternator’s rectifier, where it’s converted into direct current (DC) energy, which powers the car’s electrical systems.

Learn more about what an alternator does here.

What is the ECU?

ECU stands for electronic control unit. You may also have heard it referred to as the engine control unit or engine management unit. Its job is to keep the engine running smoothly by monitoring data from sensors and making adjustments. 

It controls many things, including:

• Braking power

• Air-fuel ratio

• Idle speed

• Ignition timing

When the ECU detects a problem, it will trigger the relevant dashboard warning light.

Read our complete ECU guide here.

How do car sensors work?

Sensors are electronic devices that monitor various systems in your car and send information to the ECU. Types of sensors include:

• Lambda sensor

• Tyre pressure sensor

• Mass air flow (MAF) sensor

• Engine oil level sensor

• Coolant temperature sensor

• Air intake temperature sensor

How does an exhaust system work?

The exhaust system is designed to direct exhaust gases away from the engine and passengers while controlling emissions and limiting noise.

Here’s a quick overview of how it works:

• The exhaust manifold collects gases from the cylinders and releases them through an opening called the front pipe. 

• Next, the gases travel through the catalytic converter, which changes harmful elements like carbon monoxide into inert gases.

• The gases then pass through a silencer or muffler.

• Finally, the fumes exit via the tailpipe.

In the exhaust system of diesel cars, the exhaust gas recirculation valve (EGR) also plays an important role. Find out what it does here.

Want to know more? Our ultimate guide to car exhausts contains all the information you need.

Safety systems

From airbags to ABS, safety systems are the final piece of the puzzle, rounding off our exploration of how a car works. 

How do airbags work?

• Impact sensors around the vehicle monitor the direction and severity of a collision to determine which airbags - if any - need to be deployed.

• A small explosive device in the airbag module detonates.

• The airbags fill with air in 25 milliseconds at up to 160mph to protect the car’s occupants.

Here’s everything you need to know about airbags.

How does traction control work?

The traction control system (TCS) is a key safety system that reduces wheelspin. It has been a mandatory feature on new vehicles since 2011.

Sensors on each wheel monitor how quickly they’re spinning in relation to one another. If one is spinning significantly faster, the system detects this loss of traction and intervenes by limiting power to that wheel or applying a small amount of braking to slow it down.

Learn more about traction control.

How do anti-lock brakes work?

If you apply the brakes too suddenly or hard, the anti-lock brake system (ABS) stops the wheels from locking up. Like traction control, it’s an essential safety feature required on new cars since 2004.

Sensors located near each wheel detect when the wheel is spinning too quickly. When this happens, the ABS will automatically apply and release the brakes in a quick but controlled manner, allowing the driver to maintain control of the vehicle.

Read our full guide to anti-lock brakes here.

How do parking sensors work?

Parking sensors monitor how close a vehicle is to nearby objects and alert the driver with a beeping sound that increases in pitch as the distance gets smaller. Want to know more? Read this guide.

Your car is an incredible machine made of many interconnecting systems. By understanding how these parts work, you can take better care of your vehicle.

Want to learn more? Check out our other car ownership guides.