The engine is the heart of a car. It is a complex machine built to convert heat from burning gas into the force that turns the road wheels. Vehicles move as a result of the combination of two processes that take place in the internal combustion engine (ICE): the ignition and combustion of the fuel occurs within the engine itself. The engine then partially converts the energy from the combustion into heat and mechanical torque. In order for this to happen, the engine is made up of several individual components working simultaneously (all essential).
The internal combustion engine (ICE) is what most cars use today. For the engine to function and produce power, a mix of mainly air and fuel is required. Most car engines run on fossil fuels, primarily diesel and gasoline. Some other engines are powered by bioethanol or hydrogen. Regardless of the fuel, most car engines work on the same principle. However, there are some differences depending on the fuel used. For example, diesel engines lack spark plugs. Instead, the fuel combusts due to highly compressed hot air.
In simple terms, the way an engine produces power can be described in four steps.
- Induction – Fuel is added to the cylinder by a fuel injector, together with air
- Compression – The piston, located in the same cylinder, compresses the air-fuel mixture
- Power – As the valves close, the spark plug ignites the air-fuel mixture, producing power
- Exhaust – The piston gets forced down by the explosion, transferring the energy to the crankshaft and pushing the burned gases out to the exhaust
These four steps occur in most internal combustion engines that use gasoline. The four steps are called the “four-stroke cycle” that exists in so-called four-stroke engines.
Components of an engine
The internal combustion engine consists of many parts, with the most fundamental parts being the following:
- Engine Block
- 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.
1. Engine block
The engine block is the core of the engine. Most modern engines consist of a monobloc, meaning all the cylinders share the same block. Not only does the engine block provide space for the cylinders, but it also features 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. The most common types of internal combustion engines are listed below. Other types and variations exist but they are far less common.
V-engines, such as V6, V8, and V12 are so-called because the cylinders are aligned so they form a “V” when viewed from a front or rear-facing perspective. The number denotes the number of cylinders in the engine block. A V6 has six cylinders, while a V10 has ten cylinders, and so on.
b. Inline engine
An inline engine is configured so the cylinders are aligned in one straight row. These engines usually have 4 cylinders or fewer and are cheaper to produce.
c. Boxer engine
The boxer engine is a specific type of flat engine. The pistons lie flat, and each pair of opposing pistons simultaneously moves in and out. The movement of the pair of pistons sliding back and forth resembles that of boxers during a fight, throwing punches at each other, hence the name.
d. 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 using them. They have grabbed the attention of many car enthusiasts as the engine is capable and likes running at high RPMs.
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 tremendous forces.
After all, the power that keeps your relatively heavy car moving passes through the crankshaft. Furthermore, 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 between the crankshaft and transmission.
The transmission is connected to the output shaft, which in turn is connected to the axles. The axles are connected to the wheels, completing the journey of the power created by 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 other car components such as the alternator, camshaft, and power steering pump.
As you have seen, the piston is something that is mentioned frequently 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 attached to the piston, create a perfect seal in order to provide the compression necessary for combusting the fuel. The top part of the cylinder, the part the piston does not occupy, 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 is created and the fuel-air mixture explodes, releasing energy and producing 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 ensure that the valves open fully when the piston is in the lower position, providing fuel and air to the cylinder, and close the valves when the piston is heading toward the top of the cylinder, igniting the fuel. If your car has a timing belt, it is important to change it at 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 do so violently.
5. Fuel injector
Older 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, so did fuel. The air “dragged” the fuel with it from the carburetor’s fuel container called a “float bowl”. This was possible thanks to 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 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 defined by external mixture formation and internal mixture formation.
In general, as the name suggests, external mixture formation fuel injectors are mixed before it enters the combustion chamber. Internal mixture formation usually directly injects fuel into the combustion chamber. Modern cars have different types of sensors and other electronics that ensure the air-fuel ratio is satisfactory, with the help of the fuel injection system.
6. Exhaust manifold
When the fuel has been combusted, the exhaust gases must escape the combustion chamber. It does this while the piston is moving upwards and the exhaust valve is open. It might seem that this is a very simple process. In comparison to other components and systems in the engine, it is. However, there is also a lot of engineering behind these systems. To keep things simple, we won’t go into too much 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, providing feedback to the fuel injector system if the fuel-air ratio is too rich or lean.
Hybrid vehicle engines
By now, you should have a general understanding of how a car engine works. So far, mostly gasoline and diesel engine cars have been described, but there is a type of car that is a bit more complex: the hybrid vehicle engine. A hybrid is something created by combining two different elements. In the car world, a hybrid vehicle usually means that the car runs 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.
- A full hybrid vehicle can run on both the engine and the batteries, or with either of the two individually
- A mild hybrid vehicle does not have an electrical motor or generator that is capable of powering the car by 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, standing 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 generated by the wheels spinning is stored as electricity. In a sense, this is much like an alternator that produces electricity. However, instead of the kinetic power of the crankshaft, this energy comes from the wheels
- A plug-in hybrid is similar to a full hybrid. The difference lies in the size of the battery, as a plug-in hybrid is much bigger. You also need to plug in the car to fully charge it, hence the name plug-in hybrid
How do hybrid vehicle engines work?
The classifications above are defined by the ability of the electrical motor. In the following sections, the different types of hybrid implementation in design will be discussed. We will look at three types of hybrid designs. They are:
- Parallel hybrid
- Series hybrid
- Series-parallel hybrid
a. Parallel hybrid
Imagine a car engine producing power and transferring that power to an axis which, in turn, transfers that power to the wheels. At 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.
b. 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 key with series hybrids is that the engine is not connected to the wheels in any way. Instead, the engine is connected to a generator, which supplies 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.
c. Series-parallel hybrid
As its name suggests, the series-parallel hybrid combines 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?
Fully electric cars lack an engine. In terms of components, they have a much simpler design with no need for alternators, exhaust systems, fuel injections, cylinders, and so on. Because of the lack of a large engine, many electric cars, in addition to a trunk, possess a front trunk, sometimes called a “frunk”. This 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, while others have dual motors for the front and back axle. Some high-end electric sports cars even use a motor for every wheel. Whatever the price, electric vehicles work in very similar ways. An all-electric car consists of several components, including:
- Electric traction motor
- Thermal system
- Charge port
- DC/DC converter
- Power electronics controller
- Traction battery
There aren’t too many components, nor do they need traditional oil lubrication, an exhaust system, and so on. Thanks to this, electric cars are much easier to maintain and service than traditional internal combustion engine-powered cars.
From the outlet to the world
There are dedicated chargers for electric cars. However, most electric cars support charging from a regular outlet you have at home. How does the electricity from your home make your car drive potentially all over the world (as long as electricity is available)? Let’s look at the various components of an electric car:
a. 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 then stored in the traction battery pack.
b. DC/DC converter
The high voltage DC power that is stored in the traction battery pack is too strong for the vehicle accessories to use. To fix that problem, the DC/DC converter converts it to low-voltage DC, which can power the vehicle’s accessories. The battery stores and provides electricity for the same accessories.
c. Electric traction motor
The electric motor is what makes the wheels spin and keeps the car moving. The power comes from the traction battery.
d. Traction battery
The traction battery is the battery responsible for powering the car. They are typically lithium-ion lithium polymer batteries. Due to the large size, the battery is located at the bottom of the car.
e. 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.
g. Thermal system
The thermal system cools down the entire system. It is a very important component as the car’s performance is greatly affected by its temperature.
An internal combustion engine is a very sophisticated engine that usually runs on either gasoline or diesel. The greatest difference between gasoline and diesel engines is that a diesel engine does not rely on spark plugs but rather compression. Car engines that use two or more sources of power are called hybrids. Usually, hybrids consist of an internal combustion engine and 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.