What is An Engine? – Different Types of Engines

An engine is a machine that burns fuel and converts it into mechanical power. Most modern vehicles use internal combustion engines (ICE), which ignite fuel and use the reaction to move mechanical parts.

ICE engines burn gasoline or diesel fuel to drive pistons up and down, turning the crankshaft and eventually moving the vehicle’s wheels. Technicians measure engines by the number of cylinders and the volume of those cylinders.

For instance, a 350 V8 is an engine with eight cylinders arranged in a V formation, displacing 350 cubic inches.

It’s not uncommon to hear someone refer to the engine in their electric car, but EVs do not have engines; they have motors. Motors are machines that convert electrical energy into motion.

What is An Engine?

An engine is a machine that burns fuel and converts it into mechanical power. Most modern vehicles use internal combustion engines (ICE) that ignite the fuel and use the reaction to move mechanical parts.

Engines – such as those used to power vehicles – can run on a variety of different fuels, particularly gasoline, and diesel in cars.

However, there are some alternative fuel types such as biofuels and natural gas. In thermodynamic terms, engines are commonly referred to as heat engines that produce macroscopic motion from heat.

The heat in this case comes from the combustion of fuel in the engine, which moves pistons.

Mechanical heat engines convert heat into work via various thermodynamic processes.

The internal combustion engine is perhaps the most common example of a mechanical heat engine, in which the heat from the combustion of fuel causes rapid pressurization of the gaseous products of combustion in the combustion chamber, causing them to expand and drive a piston that rotates a crankshaft.

Unlike internal combustion engines, a reaction engine generates thrust by expelling reaction mass according to Newton’s third law of motion.

Apart from heat engines, electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy.

In biological systems, molecular motors, like myosins in muscles, use chemical energy to generate forces and ultimately motion (a chemical engine, but not a heat motor).

Chemical heat engines that use air as part of the fuel reaction are considered air-breathing engines, e.g., Rocket, deeply submerged submarines

How do Engines work?

In an 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 to work.

The engine consists of a fixed cylinder and a moving piston. The expanding combustion gases push the piston, which in turn rotates the crankshaft. Ultimately, through a system of gears in the powertrain, this motion drives the vehicle’s wheels.

There are two kinds of internal combustion engines currently in production: the spark ignition gasoline engine and the compression ignition diesel engine.

Most of these are four-stroke cycle engines, meaning four piston strokes are needed to complete a cycle. The cycle includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.

Spark-ignition gasoline and compression-ignition diesel engines differ in how they supply and ignite the fuel. 

In a spark ignition engine, the fuel is mixed with air and then inducted into the cylinder during the intake process. After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion.

The expansion of the combustion gases pushes the piston during the power stroke. In a diesel engine, only air is inducted into the engine and then compressed. Diesel engines then spray the fuel into the hot compressed air at a suitable, measured rate, causing it to ignite.

Combustion Cycle

There are thousands of controlled explosions occurring every minute the engine is running. Most internal combustion engines have a four-stroke combustion cycle:

• Intake: The air-fuel mixture gets drawn in through intake valves and sent to the cylinders.
• Compression: Both intake and exhaust valves are closed during the compression stroke. As pistons move up, the air and fuel mixture gets compressed toward the spark plugs.
• Combustion: The spark plugs ignite the air-fuel mixture with a spark, creating a small explosion. This causes the pistons to get pushed down forcefully.
• Exhaust: The final process in the cycle is the exhaust stroke. The exhaust valve opens, and gases created during combustion are expelled as the piston moves back up.

Diesel engines are also often four-stroke engines, but they’re different from gasoline-powered engines in how they complete the combustion process. Instead of using spark plugs to ignite the air-fuel mixture, they rely on high compression ratios.

Engineers measure engines by the number of cylinders and the volume of those cylinders. For example, a 350 V8 is an engine with eight cylinders arranged in a V formation and displacing 350 cubic inches.

In 2021, modern vehicle engines can be more easily understood once divided into their three primary categories, which include:

• Internal combustion engines
• Hybrid engine (Internal combustion engine + electric engine)
• Electric engine

So, let’s discuss different types of engines one by one.

Types Of Engines

Basically, engines are of two types, and these are external combustion engines and internal combustion engines.

#1. External Combustion Engine.

External combustion engines (EC engines) separate the fuel and exhaust products – they burn the fuel in a chamber and heat the working fluid inside the engine through a heat exchanger or the engine wall. The grandfather of the industrial revolution, the steam engine, falls into this category.

In some ways, EC engines work similarly to their IC counterparts – both require heat, which is obtained by burning matter. However, there are also some differences.

EC engines use fluids that undergo thermal dilation contraction or phase shifting, but whose chemical composition remains unchanged.

The fluid used can be either gaseous (as in the Stirling engine), liquid (the organic Rankine cycle engine) or undergoing a phase change (as in the steam engine) – in internal combustion engines the fluid is almost always a liquid fuel, and air mixture, which burns (changes its chemical composition).

Finally, the engines can either drain the fluid after use, as internal combustion engines do (open-cycle engines), or continuously use the same fluid (closed-cycle engines).

#2. Internal Combustion Engine.

The internal combustion engine is an engine in which the combustion of fuel takes place in a confined space called the combustion chamber. This exothermic reaction of a fuel with an oxidizer produces high-temperature, high-pressure gases that can expand.

The defining characteristic of an internal combustion engine is that the expanding hot gases do useful work by acting directly to cause movement, such as by acting on pistons, and rotors, or even pushing and moving the entire engine itself.

Two types of internal combustion engines are currently manufactured: the spark-ignition gasoline engine and the compression-ignition diesel engine.

Most of these are four-stroke engines, meaning it takes four piston strokes to complete a cycle. The cycle includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.

Spark-ignition gasoline and compression-ignition diesel engines differ in how they deliver and ignite the fuel. In a gasoline engine, the fuel is mixed with air and then sucked into the cylinder during the intake process.

After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion.

The expansion of the combustion gases pushes the piston during the power stroke. In a diesel engine, only air is drawn into the engine and then compressed. Diesel engines then spray the fuel in a suitable, metered amount into the hot compressed air, causing it to ignite.

#3. Gasoline Engines.

Most cars on the road today are powered by gasoline engines. These engines burn a mixture of gasoline and air to generate power.

They are known for their smooth operation and are suitable for a wide range of driving conditions. The air-fuel mixture is compressed to a ratio of between 8:1 and 12:1 so the energy is condensed.

When the mixture is compressed in the combustion chamber, a spark plug ignites it, causing an explosion that forces the piston downward.

#4. Diesel Engines.

Diesel engines, commonly found in trucks and some passenger vehicles, operate on diesel fuel. These engines are known for their fuel efficiency and torque, making them ideal for heavy-duty applications. In these engines, the air-fuel mixture is compressed to a ratio of between 14:1 to 22:1 typically.

When it’s compressed, the kinetic energy is quicky forced to an extreme level, and the temperature skyrockets. The mixture doesn’t need a spark to ignite it – instead, it combusts on its own.

#5. Forced Air Induction.

Two other designs are adaptations on gas and diesel engines: turbocharging and supercharging. Turbocharging involves compressing the air by a turbine in the exhaust before it enters the combustion chamber.

It results in more air and fuel being burned, and thus, more power. Turbocharged engines are popular in performance-oriented gas vehicles, and many diesel engines use turbos to produce higher horsepower and torque too.

Similar to turbocharging, supercharging increases the amount of air entering the engine but uses a different method. A supercharger is driven by a belt connected to the engine’s crankshaft, providing instant power and responsiveness.

You typically only see superchargers on gas engines.

#6. Electric Motors.

As technology continues to advance, electric vehicles (EVs) are becoming increasingly prevalent on our roads. Electric motors offer a different approach to powering vehicles, relying on electricity stored in batteries rather than traditional combustion processes.

Electric motors operate on the principle of electromagnetism. When an electric current flows through a coil of wire in the presence of a magnetic field, it generates a force that causes the rotor to turn.

These rotors are in a direct-drive electric motor that could drive a pair of wheels, or there could be two or four motors in one vehicle. In EVs, this process is powered by lithium-ion batteries, which store and deliver electricity to the motor.

Electric motors offer plenty of advantages, such as instant torque, quiet operation, and zero emissions. As technology evolves, electric vehicles are becoming more accessible and practical for everyday use.

#7. Hybrid Engines.

Hybrid vehicles combine the benefits of internal combustion engines and electric motors, offering a versatile, efficient powertrain.

These vehicles can operate on electric power at lower speeds and seamlessly switch to the combustion engine for higher speeds or when additional power is needed.

Advantages of hybrid technology include:

• Fuel efficiency – Hybrids achieve better fuel efficiency by utilizing electric power for city driving, where combustion engines are less efficient, and seamlessly transitioning to the combustion engine on the highway.
• Reduced emissions – The electric mode of hybrid vehicles produces zero emissions, contributing to a cleaner environment, especially during stop-and-go traffic.
• Regenerative braking – Hybrids often incorporate regenerative braking, where the kinetic energy during braking is converted into electrical energy and stored in the battery, recouping a small amount for later use.

#8. Rotary Engines.

Rotary engines, also known as Wankel engines, offer a distinctive alternative to traditional piston-driven engines. Instead of pistons moving up and down, rotary engines use a triangular rotor that spins in a circular motion within a housing.

They produce similar power to a small V6 in a much lower-displacement design. Mazda made them popular with the introduction of the Cosmo, RX-7, and RX-8 models.

Why is this car engine desirable? Reasons include:

• High RPM and smooth operation – Rotary engines can achieve high revolutions per minute (RPM) and get there faster, and they operate more smoothly than traditional engines due to their simple design with fewer moving parts.
• Compact size – Rotary engines are inherently compact, making them suitable for applications where space is a constraint, such as in sports cars.
• Unique sound and performance – The design of rotary engines results in a distinct sound and performance characteristics, appealing to enthusiasts seeking something different.

Whether you’re driving a traditional gasoline-powered car, exploring the world of electric vehicles, benefiting from hybrid technology, or enjoying the unique characteristics of a rotary engine, each type has its advantages and applications.

As technology continues to evolve, the automotive landscape will undoubtedly witness further innovations in the realm of car engines.

Types of Engines’ Layouts

While most vehicles use internal combustion engines, the setup of these engines can vary. The cylinder layouts can vary, depending on the amount of power a manufacturer wants the car to have or to ensure the engine will fit the space that’s allotted.

The most common cylinder layouts include:

• Straight: Cylinders in a straight engine layout are arranged in a line parallel to the car from front to back. This allows more cylinders to fit, making this layout popular for powerful sedan models.
• Inline: Inline engines feature cylinders that are arranged side-by-side and upright. This is a popular configuration since it allows for a smaller, compact engine.
• V: When viewed from the front, the cylinders in a V-engine are arranged in a V-shape. They feature the cylinders arranged at a 60-degree angle. These engines allow a lot of cylinders to fit and are often found in high-performance models.
• Flat: Also referred to as a boxer engine, the cylinders lie horizontally. This engine type is uncommon and is most often found in Porsche vehicles. They do offer the benefit of a low center of gravity within the engine bay.

#1. V Style Engines.

This used to be the most common car engine on the market and is still heavily used by car manufacturers today.

V-engines, one of the most common engine types, have their cylinders arranged in a V-shape and always have an even number of cylinders – the same number on either side of the V.

These engines are usually arranged at a 90-degree angle and are typically found in 6, 8, 10 or 12 cylinders.

V Engines Pros and Cons:

• V-type engines usually boast of high-quality engine displacement and a rigid design.
• They are expensive to maintain and complex for people to understand.
• Compact and allows for more cabin space.
• Ideal for larger family vehicles, trucks, and other automobiles where greater power and towing capacity are required.

Examples of vehicles commonly found in our inventory section with V-style engines include:

• Ford Expedition
• Honda Ridgeline
• Ford F-150
• Honda Odyssey

#2. Inline Engines.

In-line (or “straight”) engines have all the cylinders in a row, meaning they tend to be longer than the V configuration. For this reason, in-line engines are usually found in 3-, 4-, 5- and 6-cylinder variants, as 8 cylinders in a row would be too long to fit in most engine compartments.

BMW is famous for its powerful “line sixes” (in-line 6-cylinder engines). In-line four-cylinder engines have been extremely popular in recent years due to their affordability, fuel economy, and reduced emissions.

Some examples of great, quality used vehicles that have inline engines are:

• Mitsubishi Mirage
• Honda Accord
• Buick Regal
• Chevrolet Cruze

Pros and Cons of an Inline Engine

• These engines are compact and lightweight.
• They are easy to fix.
• They are rather delicate engines.

When shopping for a used sedan, compact, or fuel-efficient vehicle, you should expect to find one with a 4-cylinder inline engine. Their compact size, lightweight materials, and good fuel efficiency make them ideal for powering smaller-sized passenger vehicles.

#3. Flat Engines.

Flat engines (also known as “boxer” engines) are arranged with the cylinders aligned horizontally so that when they fire, they face each other (as if boxing each other). A boxer engine is essentially a V-style engine where the V is opened to lie flat. Boxer engines are known to be used in Porsches and some Subaru models.

Motorcycles, such as the ones made by BMW in 2021, largely rely on two-cylinder flat engines.

High-performance vehicles with flat engines have included the JaguarXK6,

Pros and Cons of Flat Engines

• Vehicles with flat engines are well-balanced and easy to handle.
• They can be huge engines and rather complex to understand.

#4. Rotary Engines.

A rotary engine is an internal combustion engine, like the engine in your car, but it works very differently from the traditional piston engine.

In a piston engine, the same volume of space (the cylinder) alternately performs four different tasks – intake, compression, combustion and exhaust. A rotary motor does the same four jobs, but each happens in its own part of the case.

It’s like having a separate cylinder for each of the four jobs, with the piston continuously moving from one to the next.

Pros and Cons of Rotary Engines

• These engines are simple to understand.
• They are durable engines.
• Very hard to find skilled mechanics in case of failure.

Cylinder Configurations

The number of cylinders a vehicle has helps determine the amount of power an engine can produce. Items like turbochargers allow for extra compression in the combustion chamber, meaning engine power can be increased without adding more cylinders.

The smallest engine configuration is a twin-cylinder, but these don’t offer much power or capacity. However, they are sometimes found on smaller eco-friendly engines.

Three-cylinder engines typically are arranged in a straight-engine layout and can sometimes be found on smaller vehicles or hatchbacks. This compact design provides good fuel economy, and cars can still have a decent amount of power with the addition of a turbocharger.

The most common engine configuration is the four-cylinder, which is found on a variety of vehicles from small to midrange. A four-cylinder engine is set up in an inline design and offers a good amount of engine output.

The number of cylinders in an engine can continue to increase, like six-cylinder engines that are found on high-end performance and sports cars.

FAQs.