What are engines and Types of Engines

The exterior of a car defines its beauty while the interior tells what the car can do for us. We hardly ever pay attention to the engine, which is a car’s most crucial component. The engine is the first thing on the minds of car enthusiasts, but for the common man, it is probably the last. Don’t just assume that power and mileage numbers are the only information that matters. Knowing a little bit more about your car’s engine can help you make the best choice for your needs and minimize servicing costs. Let’s start with what is an engine.

Table of Contents

• What is an Engine?
• Internal Combustion Engine
• External Combustion Engine
• Engine Types Based on Number Strokes
• Engine Types Based on Design of Engine
• Engine Types Based on Ignition Method
• Engine Types Based on Number of Cylinders
• Engine Types Based on Arrangement of the Cylinders
• Engine Types Based on Valve Arrangement
• Engine Types Based on Type of Cooling
• Engine Types According to Air-intake Process

What is an Engine?

Prior to hybrid and electric-powered vehicle engines, a car’s engine could easily be described as a machine that facilitates the internal combustion of energy-producing liquids like diesel and petrol. However, since the introduction of hybrid and electric cars, explaining how a modern car engine works requires a bit more information and know-how. Modern car engines are complicated and specifically designed to meet various customer needs. A few people prefer more power, while others focus only on fuel efficiency. To satisfy the needs of every customer, car manufacturers have devised several different car engine types over the past few decades. Today, we are going to explain each type of car engine out there to increase your knowledge about engines. The major distinction between engines is internal combustion engine and external combustion engine. So let’s start with internal combustion engine.

Internal Combustion Engine

An internal combustion engine is a type of heat engine where the combustion of fuel takes place inside the chamber. When the fuel burns inside the engine, it causes the temperature and pressure to increase. This high pressure produced by combustion is then applied directly to power pistons, rotors, or a nozzle. It’s the force that moves your car over a distance, transforming chemical energy into useful mechanical energy. These engines are generally used in the automobile industry to power cars. An internal combustion engine can be categorized on many bases, for instance, type of ignition, number of strokes, design, and so on. To understand the steps of how a four-stroke internal combustion engine works, the four strokes are used: intake, compression, power, exhaust. In the intake stroke, the piston starts the process by descending and drawing air into the cylinder via intake valves. Then, fuel is delivered into a cylinder that houses the piston. In the compression stroke, the intake valves close, allowing the piston to move back up, thereby compressing the air and fuel within the cylinder. In the power stroke, a spark plug ignites the compressed fuel-air mixture to create a small explosion. The process is repeated continuously when the engine is running. In the exhaust stroke, the waste fumes produced by the explosion in each cylinder are expelled through the vehicle’s exhaust system.

External Combustion Engine

As the name suggests, in an external combustion engine, combustion of fuel takes place outside the engine. Here, the extra heat is utilized to produce low-pressure steam, which is used in the turbine to produce electricity. In this type of engine, the fuel is burned outside the engine, so we can also use solid fuel. External combustion engines are not used in cars.

Engine Types Based on Number Strokes

First is the two-stroke engine. In a two-stroke engine, a piston completes a power cycle with two strokes – one up and one down inside the cylinder – to complete one crankshaft revolution during a single fuel burn. In this type of engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, which means the intake and exhaust functions occur at the same time.

Next is the four-stroke engine. A four-stroke engine is an internal combustion engine variant in which the piston completes four strokes while turning a crankshaft. The piston moves two times up and down inside the cylinder and completes two crankshaft revolutions. This type of engine offers high mileage compared to two-stroke engines.

There’s also the six-stroke engine, although it’s in its development phase. The six-stroke internal combustion engine is already creating a lot of buzz in the motor industry. It has several dedicated advantages over traditional motors and may result in increased fuel efficiency, reduced mechanical complexity, and lower emissions.

Engine Types Based on Design of Engine

Now let’s explore engine types based on the design of the engine.

First is the reciprocating engine. The main component of a reciprocating engine is a piston, which is used to convert pressure into a rotating motion. There may be one or more pistons in an engine, each of them located inside a cylinder. When pressurized gas is injected and heated inside the cylinder, the piston initiates reciprocating or to-and-fro motion.

Next is the Wankel engine, also known as a rotor engine, which uses an eccentric rotary system to convert pressure into rotating motion. It is simpler, smoother, and much more compact compared to its more popular competitor, the reciprocating or piston engine. Wankel engines are often used in racing cars.

Engine Types Based on Ignition Method

Now let’s categorize engines based on the ignition method.

There’s the compression ignition engine, where the combustion of fuel in the chamber is triggered by the high temperatures achieved by gas or air due to adiabatic compression. Diesel engines are a perfect example of a compression ignition engine.

On the other hand, there’s the spark ignition engine. All petrol engines are based on spark ignition, where a spark plug ignites the combustion of the air-fuel mixture. Even though spark ignition engines are commonly referred to as petrol engines, they can also run on auto gas, methanol, bioethanol, compressed natural gas, hydrogen, and nitromethane.

Next is the electric motor. Unlike traditional internal combustion-powered cars, electric cars get power from their pre-installed rechargeable batteries. Electric motors convert electrical energy into mechanical energy and are more effective than traditional internal combustion engines in converting stored energy. Most electric cars either use lithium-ion or lead-acid batteries.

There’s also HCCI (Homogeneous Charge Compression Ignition) technology, which combines the characteristics of conventional gasoline engines and diesel engines to produce a hybrid solution. HCCI engines rely on a precise mixture of fuel and air that is compressed until it spontaneously combusts without the need for a spark or fuel injection. This combustion process results in high fuel efficiency and lower emissions compared to traditional engines, making HCCI engines a promising technology for the future of transportation.

Engine Types Based on Number of Cylinders

Let’s categorize engines based on the number of cylinders.

There’s the single-cylinder engine, which has only one cylinder connected to the crankshaft. Single-cylinder engines are compact, lightweight, and have a better weight-to-power ratio. They are used in motorcycles, motor scooters, dirt bikes, and go-karts.

On the other hand, there’s the multiple-cylinder engine, which has more than one cylinder. It can be either a two-stroke or four-stroke engine, either diesel or spark ignition. Multiple-cylinder engines are capable of achieving higher revolutions per minute and have a superior capability to neutralize imbalances.

Engine Types Based on Arrangement of the Cylinders

Now let’s explore engine types based on the arrangement of the cylinders.

In the inline engine, cylinders are arranged in a straight line, one behind the other along the length of the crankshaft. Inline-4 is the most popular in the automotive industry as it is compact, fuel-efficient, and gives a higher power-to-weight ratio than Flat-6 or 8 engines.

Next is the V-type engine, where the cylinders and pistons are aligned in two separate planes in such a way that they appear to be in V-shape when viewed from the top. The unique shape of this engine substantially reduces the overall engine weight and length compared to inline engines.

There’s also the W engine, a type of internal combustion engine featuring a unique configuration in which the cylinders are arranged in a W shape. This design allows for a high cylinder count and compact packaging, making W engines popular in high-performance and luxury vehicles.

An opposed-piston opposed-cylinder engine consists of two cylinders with a piston at both ends. There is no cylinder head and thus no valves. Compared to conventional engines, the opposed-piston opposed-cylinder engine has very low bearing loads, meaning there will be less friction. This type of engine is also relatively compact and lightweight, making it suitable for use in a range of applications, including automobiles, aircraft, and marine vessels.

In the radial engine, cylinders stick out from a central crankcase like spokes on a wheel. It is referred to as a star engine because it resembles a stylized star when viewed from the front. Radial engines are generally more reliable due to a shorter crankshaft, more straightforward construction, and less vibration. Before the gas turbine engine became the dominant option, radial engines were often used for aircraft engines.

Engine Types Based on Valve Arrangement

Now let’s categorize engines based on valve arrangement.

There’s the I-head engine or overhead valve engine, where the valves are located in the cylinder head. Inline engines usually have the valves in a single row, while V8 engines may have the valves in a single row or in a double row in each bank.

Next is the L-head engine, where the inlet and exhaust valves are located side by side and operated by a single camshaft. The combustion chamber and cylinder form an inverted L.

The F-head engine combines L-head and I-head engines, with one valve (usually the inlet valve) in the head and the exhaust valve in the cylinder block. Both sets are driven from the same camshaft.

There’s also the T-head engine, which has the inlet valves on one side and the exhaust valves on the other side of the cylinder. Thus, two camshafts are required to operate them.

Engine Types Based on Type of Cooling

Now let’s categorize engines based on the type of cooling.

Air-cooled engines are used in motorcycles and scooters. In air-cooled engines, the cylinder barrels are usually separate and equipped with metal fins, providing a large radiating surface to increase the rate of cooling. Many air-cooled engines have metal shrouds that direct the airflow around the cylinders for improved cooling. Since these engines do not use water, the problem of cold weather maintenance is eliminated.

On the other hand, water-cooled engines are used in buses, trucks, cars, and other four-wheeled heavy-duty motor vehicles. These engines use water with an anti-freeze compound added to serve as the cooling medium. The water is circulated through water jackets around each of the combustion chambers, cylinders, valve seats, and valve stems. After passing through the engine jackets in the cylinder block and cylinder head, the water is passed through the radiator, where it is cooled by air drawn through the radiator.

Engine Types According to Air-intake Process

Lastly, let’s categorize engines based on the air intake process.

There’s the naturally aspirated engine, which depends solely on atmospheric pressure for air intake and does not rely on forced induction through a turbocharger or a supercharger. Many sports cars specifically use naturally aspirated engines to avoid turbo lag.

Supercharged and turbocharged engines have some fundamental differences. A supercharger uses a crankshaft to drive energy and produce power, rather than an exhaust stream like in turbochargers. Superchargers are connected directly to the engine via a belt and can achieve speeds up to 50,000 RPM. In contrast, turbochargers are not directly connected to the engine and can go up to 15,000 RPM. Moreover, turbochargers are equipped with smog-altering instruments that lower carbon emissions, making them more eco-friendly than superchargers.