How Does A Car Engine Work?

When it comes to car engines, there is a lot of different terminology and technologies to consider. Here is the ultimate guide to car engines.

The engine makes your car move with the help of very sophisticated technology.

In this guide, you will find out how an engine works, but also how hybrids and electric motors work.

Let’s just right into the basics of car engines!

Table of ContentsShow

The Basics Of A Car Engine

The internal combustion engine (ICE) is what most cars are using today. For the engine to run and produce power, a mix of mainly air and fuel is needed.

Most car engines run on fossil fuels, mainly diesel and gasoline. Some other engines are powered by bioethanol or hydrogen.

Regardless of fuel, most car engines work by the same principle. Some differences are depending on the fuel used.

For example, diesel engines lack spark plugs, instead, the fuel combusts due to highly compressed (and therefore hot) air.

Power Generation

car engine

In simple terms, the way an engine produces power can be described in four steps.

  1. Induction: Fuel is added to the cylinder by a fuel injector, together with air.
  2. Compression: The piston, located in the same cylinder, compresses the air-fuel mixture.
  3. Power: As the valves close, the spark plug ignites the air-fuel mixture, producing power.
  4. Exhaust: The piston gets forced down due to the explosion, transferring the energy to the crankshaft and pushing the burned gases out to the exhaust.

These four steps are present in most internal combustion engines that use gasoline. These four steps are called the “four-stroke cycle” that exists in so-called four-stroke engines.

Components Of An Engine

car engine with hoses

The internal combustion engine consists of many parts, with the most fundamental parts being the following:

  • Engine Block
  • Crankshaft
  • Piston
  • Camshaft
  • Fuel Injector
  • Exhaust Manifold

All these parts and more are typical components of a four-stroke internal combustion engine, which is used by most cars that run on fossil fuel.

The components mentioned above are responsible for creating power, but many other components and systems are needed to make the engine run. This includes a lubrication system, cooling system, starting system, Engine Control Unit (ECU), and more.

The above list will be explained, and later on, it will be shown how they all act in a lovely symphony to produce power and get your vehicle moving.

Engine Block

car engine

The engine block is the core of the engine. Most modern engines consist of a monobloc, meaning that all the cylinders are sharing the same block.

Not only does the engine block provide space for the cylinders, but it also oil galleries and coolant passages, enabling the engine to get lubricated and cooled, respectively.

You may have heard of engines being called V8, V12, inline 4, boxer engine, and so on. These names are dictated by how the cylinders are aligned in the engine block.

Below, the most common types of internal combustion engines are listed. Other types and variations exist but are not very common.


V-engines, such as V6, V8, V12 are called so because the cylinders are aligned so they form a “V”, seeing it from a front- or end-facing perspective.

The number denominates the number of cylinders in the engine block. A V6 has six cylinders, while a V10 has ten cylinders, and so on.

Inline Engine

An inline engine is configured so that the cylinders are aligned in one straight row. These engines usually have 4 cylinders or less and are cheaper to produce.

Boxer Engine

The boxer engine is a specific type of flat engine. The pistons are lying flat, and each pair of opposing pistons simultaneously moving in and out.

The movement of the pair of pistons moving together back and forth resembles that of boxers before a fight, hitting their gloves back and forth, hence the name.

Rotary Engine

Wankel engines, also called rotary engines, do not use pistons at all. Instead, they use a rotor in the shape of a triangle.

Today, rotary engines are very rare with only a few car models having them equipped. It has caught the attention of many car enthusiasts as the engine is capable and likes running on high RPMs.

The Crankshaft

engine crankshaft

The pistons are exposed to the reactions happening in the combustion chamber. When the fuel ignites, the energy forces the pistons down.

The pistons are connected to the crankshaft by connecting rods. As the pistons move, so does the crankshaft. The up-and-down movement from the pistons translates to a rotational movement at the crankshaft.

The crankshaft is exposed to enormous forces, after all, the power that keeps your relatively heavy car moving goes through the crankshaft. Not to mention that a lot of the energy in the crankshaft is lost through friction.

As the crankshaft converts the linear movement into rotational, the flywheel smooths out the power. The delivery of power continues to the transmission, where a clutch is located in between the crankshaft and transmission.

The transmission is connected to the output shaft, which in turn are connected to the axles. The axles are connected to the wheels, finishing the journey of the power created from the cylinder.

The crankshaft does not only deliver rotational power to the transmission. As it rotates, pulleys connected to the crankshaft are in turn connected to accessory belts that power on other car components such as the alternator, camshaft, and power steering pump.


auto pistons and connecting rods

As you have seen through the text, the piston is something that is mentioned a lot in the process of creating power in an internal combustion engine.

The piston is enclosed in the cylinders of the engine block. Nothing leaks or escapes from the piston as the piston rings, which are on the piston, make a perfect seal in order to provide the compression needed for combusting the fuel.

The top part of the cylinder, that is, the part where the piston is not occupying, is called the combustion chamber. The combustion chamber becomes smaller and smaller as the piston moves up, toward the top of the cylinder.

As the piston moves up, and the combustion chamber becomes smaller, a great amount of heat and pressure occurs and the fuel-air mixture explodes, releasing energy and providing power.

As previously mentioned, diesel engines do not rely on spark plugs instead the fuel is ignited by the massive compression caused by the piston making the combustion chamber “smaller”.



As mentioned in the crankshaft section, the camshaft is connected to the crankshaft, providing synchronous movement in the engine block.

The camshaft operates the intake and exhaust valves, allowing air and fuel into the combustion chamber.

You may have heard of timing belts or timing chains; these are what connect the crankshaft and the camshaft. They make sure that the valves open fully when the piston is in the lower position, providing fuel and air into the cylinder, and close the valves when the piston is headed toward the top of the cylinder, igniting the fuel.

If your car has a timing belt, it is important to change it in intervals determined by your car manufacturer. Failure of the timing belt can lead to huge engine damage as engine components that are not meant to touch each other are violently doing so.

Fuel Injector

bad fuel injector

Previously gasoline engine cars used carburetors. When your right foot pressed the gas pedal, the throttle valve would open, letting air move through the carburetor.

As the air passed through the carburetor, fuel did so as well. The air “dragged” the fuel with it from the carburetor’s fuel container called float bowl.

This was possible with fancy physics, or more specifically, by Bernoulli’s principle, which made the air and fuel relatively proportional.

The air-fuel mixture would then proceed to the intake manifold and then to the intake valves, where combustion would occur in the cylinder.

Today, a fuel injector is used which provides a more precise amount of fuel through a nozzle. There are also different types of fuel injectors, mainly branched by external mixture formation and internal mixture formation.

In general, as the name would imply, external mixture formation fuel injectors are mixed before it goes into the combustion chamber. Internal mixture formation usually directly injects fuel into the combustion chamber.

Modern cars all have different types of sensors and other electronics that make sure the air-fuel ratio is satisfactory with the help of the fuel injection system.

Exhaust Manifold

exhaust manifold

When the fuel has been combusted, the exhaust gases must escape the combustion chamber. It does so while the piston is moving upwards while the exhaust valve is open.

Initially, one may think this is a very simple process, compared to other components and systems of the engine, it is. However, there is also a lot of engineering behind these systems.

To keep it simple, we won’t go a lot into detail. If you would like to find out more about the exhaust manifold and the engineering behind it, Wikipedia has a great and concise article about it.

It is worth mentioning that unburnt fuel also goes through the exhaust manifold. An oxygen sensor is equipped in the manifold, giving feedback to the fuel injector system if the fuel-air ratio is too rich or lean.

Hybrid Vehicle Engines

What Is A Hybrid Car And How Do They Work?

By now, you should have a general understanding of how a car engine works. Till now, mostly gasoline and diesel engine cars have been mentioned, but there is a type of car that is a bit more complex – the hybrid vehicle engine.

A hybrid is a thing made by combining two different elements. In the car world, a hybrid vehicle usually means that the car is running on two types of power – electric and gasoline. 

Generally, there are three types of hybrid vehicles:

  • Full hybrid
  • Mild hybrid
  • Plug-in hybrids

These types are divided depending on the degree of the hybridization.

In short, a full hybrid vehicle can run on both the engine and the batteries, or with either of those individually.

A mild hybrid vehicle does not have an electrical motor or generator that is capable of powering the car itself.

Mild hybrids use an electric motor that also replaces the traditional alternator. The electric motor assists the car and saves fuel by, for example, shutting down the internal combustion engine when coasting, being still, or braking.

It can also assist the internal combustion engine when accelerating and some also support regenerative braking.

When regenerative braking is active, the kinetic energy of the wheels spinning gets stored as electricity. In a way, it is just like an alternator that produces electricity, but instead of the kinetic power of the crankshaft, it comes from the wheels.

A plug-in hybrid is similar to a full hybrid. The difference is in the size of the battery, as the plug-in hybrid is much bigger. You also would have to plug in the car to fully charge it, hence the name plug-in hybrid.

How Do Hybrid Vehicle Engine Work?

Honda hybrid

The classification above is defined by the ability of the electrical motor. In the following text, the different types of hybrid implementation in the terms of design will be discussed.

Three types of hybrid designs will be discussed, they are:

  • Parallel hybrid
  • Series hybrid
  • Series-parallel hybrid

Parallel Hybrid

Imagine a car engine producing power and transferring that power to an axis which is, in turn, transferring that power to the wheels. On the other end, you have an electrical motor transferring its power to the same axis.

This is the basic principle of a parallel hybrid. Both the internal combustion engine and the electric motor send power to the same axis. In most cases, the electrical motor is between the engine and the transmission.

Series Hybrid

You may have heard of “extended-range electric vehicles”. They are hybrids that use both electric motor(s) and an internal combustion engine.

The trick with series hybrids is that the engine is not connected to the wheels in any way. Instead, the engine is connected to a generator, supplying electricity for the electric motor.

The internal combustion engine turns on when there is no more charge in the battery, powering the electric motor directly. It can also be used to charge the battery.

Series-Parallel Hybrid

As the name suggests, the series-parallel hybrid combines both the design of the parallel hybrid and the series hybrid.

In other words, the internal combustion engine provides power to both the wheels and a generator.

How Do Electric Vehicles Work?

electric vehicle

Fully electric cars lack an engine. In terms of components, it is a much simpler design with no need for alternators, exhaust systems, fuel injections, cylinders, and so on.

Because of the lack of a big engine, many electrical cars, besides a trunk, possess a front trunk or a so-called “frunk”. It may come in handy as it provides more storage space in the car. 

Instead of an engine, one or several electric motors are used. The motor placement varies according to the model of the car. Some have it exclusively on the front axle, others have dual motors in the front and back axle.

Some high-end electric sports cars even use a motor for every wheel. Regardless of the price, electric vehicles work in very similar ways.

An all-electric car consists of a few components, including:

  • Battery
  • Electric traction motor
  • Thermal system
  • Charge port
  • DC/DC converter
  • Power electronics controller
  • Traction battery
  • Transmission

These components are not many, nor do they need traditional oil lubrication, an exhaust system, and so on. Because of that, electric cars are much easier to maintain and service than traditional internal combustion engine-powered cars.

From The Outlet To The World

electric motor

There are dedicated chargers for electric cars, however, most electric cars support charging from a regular outlet you have at home.

So how does the electricity from your home make your car drive potentially all over the world (as long electricity is available)?

Let us go through the components of the electric car:

Charge Port

The first step is to charge your car by plugging the charger into the charge port. The alternating current (AC) goes through the onboard charger which converts it into direct current (DC), which is stored in the traction battery pack.

DC/DC Converter

Because of the high voltage DC power that is stored in the traction battery back is too high for the vehicle accessories to run. To fix that problem, the DC/DC converter converts it to low-voltage DC powering the vehicle accessories.

The battery stores and provide electricity for the same accessories.

Electric Traction Motor

The electric motor is what makes the wheels spin and the car going. The power comes from the traction battery.

Traction Battery

The traction battery is the battery responsible to power the car. They are typically lithium-ion lithium polymer batteries. Due to the big size, the battery is located at the bottom of the car.

Power Electronics Controller

The power electronics controller is the brain of the electric processes. It determines the speed of the electric motor, the energy delivered to the battery, and more.


The transmission transfers the power from the electric motor to the wheels. Unlike traditional internal combustion engines, the transmission in most electric cars only has one gear.

Thermal System

The thermal system cools down the whole system. It is a very important component as the performance is greatly affected by the temperature.


2021 Tesla Model S
A Tesla Model S

An internal combustion engine is a very sophisticated engine that usually runs on either gasoline or diesel. The greatest difference between gasoline and diesel engine is that a diesel engine does not rely on spark plugs but compression.

Car engines that use two or more sources of power are called hybrids. Usually, hybrids consist of an internal combustion engine with an electric motor.

The hybrids can either be categorized by design or by the extent of the hybridization. Most hybrid cars use a series-parallel hybrid design where the internal combustion engine provides power to both a generator and the wheels.

An all-electric car has fewer components than a traditional engine. They are much easier to maintain as they have fewer parts and do not need to be lubricated by any oil, for example.

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Bajro Muric
Bajro Muric

Bajro is a big car enthusiast with a love for writing and teaching. He writes about anything regarding cars - from common problems and fixes to racing.