Types of Engines and their Comparison

Introduction:

The cylinder is the power unit of the engine where fuel is burned and converted into mechanical energy that powers the vehicle. This means the more cylinders you have the more power you have. The number of cylinders in a typical car could be four, six, or eight. These different types of engine layouts every in their cylinder arrangements. However, the basic principles of an internal combustion engine are universal, and how these engines are designed and function varies greatly. Some engine configurations are designed inline others in a V. While others are flat.

Single-Cylinder engine:

Single cylinder engine is a piston engine with one cylinder. This engine is often used for motorcycles scooters go-karts and all-terrain vehicles. Single-cylinder engines are made both as four strokes and two strokes.  The first gasoline engine developed by KARL BENZ was a one-cylinder two-stroke unit that ran for the first in 1879.

Advantages:

• Single-cylinder engines are less expensive to build due to the greater potential for airflow around all sides of the cylinder air.
• Cooling is often more effective for single-cylinder than multi-cylinder engines.
• Single-cylinder engines produce higher torque at lower revs making them more suitable for load-lugging and for applications where high torque is required to lower the rev range
• Comprises torque delivery at the lower end.

These are more suitable for sport bikes where the lighter component tree has to make a little more effort initially to lift the load and get moving but ultimately can deliver better performance to higher up the rec range. Most single-cylinder engines used in Motor vehicles are fueled by petrol and use a four-stroke cycle. However, diesel single-cylinder engines are also used in stationary applications.

Problems with single-cylinder engines:

In a single-cylinder engine, the size of the piston and other components is heavy for its cubic capacity as the piston goes up and down in the cylinder. It creates a force that isn’t often balanced. The primary and secondary unbalanced forces remain in the engine that causes the vibration.

A fraction of the primary unbalanced force up to 85% to 90% is made balanced by providing counterweights on the crankshaft. These counterweights are generally located at the end of the connecting rod. In some cases, war extreme methods such as a dummy connecting rod are fitted.

Application:

In the DUCATI SUPER MONO, the dummy connecting rod is attached to the same crank working the piston while the other end is attached to a weighted rocker arm. This in theory should balance out the weight of the primary piston thus reducing vibrations.

The setup also enables the engine to Rev much higher which translates to more power. These balancing devices can reduce the benefits of single-cylinder engines regarding lower weight and complexity. The uneven power delivery often means that a single cylinder requires a heavier flywheel than a comparable multi-cylinder engine resulting in relatively slower changes in engine speed.

Inline engine:

The straight or inline engine is an internal combustion engine with all cylinders aligned in one row and having no offset. An inline engine has a simple design and is often denoted as an eye engine usually found in 4,6 and 8-cylinder configurations.

8 cylinders in a row would be too long to fit in most engine Bays. They have been used in many light mediums and heavy commercial vehicles earth-moving equipment locomotives and aeronautics.

A straight engine is considerably easier to build than in horizontally opposed or V engine because the cylinder bank and crankshaft can be milled from a single metal casting requiring fewer cylinder heads and camshafts. There is an even distribution of weight hence they maintain an optimum balance. These are smaller in size and therefore need relatively small space and are comparatively cheaper.

Example:

BMW is famous for its high-performance inline six-cylinder engines

4 cylinder inline have been widespread in recent years due to their;

• Affordability
• Fuel Economy
• Reduced Emissions

Advantages:

• Inline engines have a simple design and hints are easy to construct
• Require relatively small space.

Disadvantages:

• An inline-cylinder engine lacks rigidity like V8 and V6 engines.
• There is an issue of overheating associated with these types of cylinders
• Generally, it has a higher center of gravity when compared to other types.
• Generate a loud noise on roads.

V-engine:

V-engine are one of the most common engine types and they have their cylinders configured in a V-shape. It consists of two cylinder banks usually with the same number of cylinders in which each bank is connected to a common crankshaft.

In most cars today if the number of cylinders is more than 4. It will most likely be a V-type arrangement the typical examples are V6, V8, V10, or V12.

• The V-type engines are very smooth and balanced.
• When the number of cylinders increases the V-type arrangement offers better benefits and due to their shorter length.
• They are way more compact than the inline type.
• Compared with the less common flat engine.  A V engine is narrower, Taller, and has a high center of mass.
• The V engine between the cylinder banks varies significantly between the engines. Some of them have used a V angle of 180at the same angle as a flat engine such as several Ferrari V12
• At the other end of the scale the launch of V4 and the Volkswagen VR6 uses the angle of 15along with a single cylinder head used by both Banks of cylinders.
• The engine balance of a V12 engine is that perfect primary and secondary balance. Each bank of the V12 engine functions has a straight 6-engine which by itself has perfect primary and secondary engine balance.
• By using the correct V angle a V12 engine can therefore have a perfect balance.

Advantages:

• It has a smaller size than the other engines and improves aerodynamics.
• They increased primary balance and reduce vibrations.
• They provide smoother operation for high-speed performance.
• Compactness of V engines makes them suitable for high-end sports cars.
• High-end superbikes use a V4 design and high-end cars such as saloons, sports cars, and SUVs commonly employ the V6 and V8 designs.

Disadvantages:

• It can be more expensive because they have more parts than inline engines.
• Due to its complex design. It is difficult to build a V engine for auto manufacturers.
• Cooling is another problem of the V engines.
• More components can make the engine heavier.
• V engines are generally not very fuel efficient therefore cars equipped with V engines generally fall into luxury and sports categories.

Flat engines:

Flat engines are horizontally opposed piston engines and have been around since the 1890s. A flat engine is a 180 V engine that works similarly to other V engines. Each pair of cylinders shares a single crank pin so that one piston moves inward and the other moves outward.

• The two opposing pistons will move in the same direction but one is compressing and the other is combusting.
• One piston will be at the top dead center and the other will be at the bottom dead center.

Advantages:

• Compared with the more common straight engines have better primary balance resulting in less vibration.
• Flat engines are famous for having perfect balance and offer sports cars high performance and power without vibrations
• Their low center of gravity can improve the aerodynamics of the vehicle.
• Flat engines are fairly easier to cool thanks to their horizontally opposed profile.

Disadvantages:

• The problem with these engines is that flat engines are wider than comparable inline or V engines.
• Repairs and maintenance can be an issue since the heads are basically on the side of the car.

Boxer Engine:

Flat engines are not boxers but boxer engines are flat. Due to their low height, they are also known as Pancake engines.

• The boxer engine is a horizontally opposed internal combustion engine that is designed with opposing cylinders on each side of a central rotating crankshaft.
• Each opposing piston will do the same stroke. When the left piston is compressing the right will also be compressing. When combusting the second will also be combusting and so on.

Applications:

• Currently PORSCHE, SUBARU, andTOYOTA are the only manufacturers that offer boxers.
• The PORSCHE 911has always come with boxer engines and the current lineup has a variety of six-cylinder versions or flat sixes.
• The PORSCHE 718 BOXSTER, 718 CAYMAN,and 718 SPYDER have four boxers known as flat fours.
• All current SUBARU enginesare the horizontally opposed type with four cylinders.
• The Toyota 86a mechanical twin of the SUBARU BRZ also uses a flat SUBARU engine.

Advantages:

• Boxer engines offer a good rotational balance to pistons and hence lowers vibrations.
• They have a low center of gravity which is highly advantageous for maintaining stability and handling the vehicle.

Disadvantages:

• Boxer engines are larger and hence occupy a lot of space.
• Maintaining these engines is difficult and expensive.
• It has a comparatively long production time.

W-engine:

A W-engine is a type of piston engine where there or four-cylinder Banks use the same crankshaft resembling the letter W when viewed from the front. W engines with three banks of cylinders are also called broad Arrow engines because of the resemblance. W engines are less common and are typically shorter and wider than V engines. The angle between the V in a regular V engine is around 60 to 90. However, the V and W engine is about 15.

• Over the year the W engine has been available in 3, 6, 8, 12, and 16-cylinder configurations.
• The biggest ever was W30 used in a SHERMAN tank during WORLD WAR 2.
• The VOLKSWAGEN AG more commonly known as VAG is responsible for the mass production of the W-type engine.

Advantages:

• W engines are used in heavy-duty luxury and exotic cars because they take up less space and provide more power.
• The W-engine is a better version of the V engine in terms of its compact size.

Disadvantages:

• The engine is compact but uses lots of components to stay together.
• The more components make it complicated for the auto manufacturers to produce it at a mass scale. This is the reason why W engines are very rare.

WANKEL Rotary engine:

The rotary engines are truly a unique concept and have been made successful by MAZDA. It was invented by German Engineer FELIX WANKEL. It consists of a three-lobe rotor of a triangular shape with curved sides that rotates eccentrically in an oval chamber. The rotor is mounted on the crankshaft through the external and internal gears.

• A WANKEL rotary engine has an ignition system and a fuel delivery system that are similar to the ones on piston engines.
• WANKEL rotary engines use the 4-stroke combustion cycle which is the same cycle that four-piston engines use but it is accomplished in a completely different way.

Advantages:

• Rotaries typically outperform piston reciprocating engines in endurance, performance, and simplicity of operation and maintenance.
• There aren’t many moving parts.
• The WANKEL design is;
• Extremely smooth
• Compact
• Lightweight
• Also it is not mounted vertically
• There are no pistons.
• The center of gravity is very low.

Problems with WANKEL rotary engine:

The problems with the WANKEL engine is that they;

• Tend to suck gas.
• Deliver poor emission
• They require frequent maintenance and are pricey to be fixed.

That’s why no one in the automotive industry is using a rotary engine nowadays. The car that’s sold with a WANKEL rotary engine was the MAZDA RX-8 which too was discontinued way back in 2012. The RX-8 had to abandon it largely to poor fuel efficiency and emissions. The Unburnt fuel, along with burned oil both result in terrible emissions.

Radial Engine:

The radial engine is a reciprocating type of internal combustion engine in which the cylinders radiate outward from a central crankcase like the spokes of a wheel. CM mainly constructed a water-cooled 5-cylinder radial engine in 1901. The radial configuration was commonly used for aircraft engines before gas turbine engines became predominant.

Radial engines have several advantages for airplanes. They can produce a lot of power. A typical radial engine in a B-17 has nine cylinders displacing 1,800 cubic inches (29.5 liters) and produces 1,200 RPM.

Working:

Radial engines work like any other four-stroke engines. They have both similar parts but their construction and design are different.  Each cylinder has an intake compression power and exhaust stroke. A radial engine cylinders are numbered from the top going clockwise with the first cylinder numbered 1. The 1 cylinder’s connecting rod is attached directly to the crankshaft and this is the master rod. The other cylinder’s rod is connected to pivoting points around the master rod. Every radial engine has an odd number of cylinders and they fire in an alternating order. So, a five-cylinder engine fires in a 1,3,5,2, and 4 order. A seven Cylinder engine fires in 1,3,5,7,2,4, and 6 orders.

Application:

This type of engine is used primarily in aviation but the radial engine isn’t exclusive to aircraft only. Throughout history, there have been tanks, cars, and bikes fitted with a radial engine.

X-engine:

X-engine is a piston engine with four banks of cylinders around the common crankshaft. The cylinders form an x-shape when viewed from the front. This X8 layout fascinated HENRY FORD and in 1920 he launched a secret project to build such an engine. But the X8 turned out to be a flawed concept and Ford finally abandoned the project in 1926 the Packard motor car company introduced the Packard X-2775 an American experimental liquid-cooled aircraft engine.

Construction:

The engine was constructed as a single crankcase with four banks of 6 cylinders in what is close to an X-configuration. The engine consisted of 260 V12 engines one upright and one inverted sharing a common crankcase.

Application:

The other example of an X-engine is the Rolls-Royce vulture a British Aero engine developed shortly before Word War 2 that was designed and built by Rolls-Royce Limited.

The vulture used the unusual X-24 configuration which was built using two Rolls-Royce Peregrine V12 engines.

U-engine:

A U engine also known as a double or twin bank engine is made up of two separate straight engines with separate crankshafts placed side by side and coupled to a shared output shaft. The engine block resembles the letter U when viewed from the front. The other variations of the U engine exist as well as square 4 engine resembles two U engines used together. This equals four straight engines all working together to share certain parts.

• The main benefit of a U-engine layout is the ability to share common parts with a straight engine upon which it is based. Additionally, if the two crankshafts rotate in opposite directions.
• The gyroscopic effect of the rotating components in each cylinder bank cancels each other out.

Applications:

• The first U engine was the Bugatti U16aircraft engine designed by EDERI BUGATTI in 1916 which had 16 cylinders and a displacement of 24.3 liters.
• In 1931, Aerial Square for motorcycles used a square 4-engine.
• In 1985, Suzuki RG500 and several related racing motorcycles used a water-cooled 4-cylinder U-engine.

H-engine:

An H engine is an engine configuration in which the cylinders are aligned so that if viewed from the front. They appear to be in a vertical or horizontal letter H. This engine comprises two flat engines with separate crankshafts most often geared to a common output shaft.

Advantages:

• The design of the H engine makes it narrow and suitable for long compact spaces where a large number of cylinders can be implemented to produce lots of pulling power.
• With the flat configuration there is excellent mechanical balance which results in less vibration.

Disadvantages:

• However, H engines are relatively heavy and high center of gravity not only because the crankshaft is located at the top of the other but also because the engine must be high enough off the ground to allow clearance underneath for the exhaust pipes.

Application:

• The most successful H engine in this form was the Napier Daggerand most famously the Napier Saber series
• The Lotus 43formula one car used a 16-cylinder H engine and an 8-cylinder H engine was used for powerboat racing in the 1970s.

Opposed-piston Engine:

The opposed type engine has two banks of cylinders directly opposite each other with a crankshaft in the center. The pistons of both cylinder banks are connected to the single crankshaft.

Advantages:

• An opposed-piston engine has an efficiency advantage because there are no cylinder heads and less heat to the cooling system.
• The quantity of pollutants generated is reduced through lower pressure and temperature during combustion.
• The longer length between the two cylinders enables the fuel to burn more fully leading to a further reduction in waste matter generation.

Disadvantage:

• The two opposing pistons power must be geared together. This added weight and complexity compared to conventional piston engines which use a single crankshaft as the power output.