How Does A Four Stroke Diesel Engine Work?

The majority of modern internal combustion engines are 4-strokes that run on either gasoline or diesel fuel. To achieve each power cycle, pistons go through four actions during engine operation. When it comes to emissions, 4-strokes mechanically segregate each event, reducing unburned fuel emissions.

What is 4 stroke diesel engine cycle?

Intake, compression, combustion (power), and exhaust are the four strokes of an internal-combustion engine. The crankshaft is turned by the piston as it moves during each stroke.

How does diesel engine work explain each strokes and cycles?

Engines with four strokes A diesel engine, like a gasoline engine, normally runs by repeating a cycle of four stages or strokes, during which the piston goes up and down twice (the crankshaft spins twice).

How does the diesel engine work?

The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which the fuel is ignited by the raised temperature of the air in the cylinder as a result of mechanical compression; it is thus a compression-ignition engine (CI engine). This is in contrast to engines that use a spark plug to ignite the air-fuel mixture, such as a petrol engine or a gas engine (using a gaseous fuel like natural gas or liquefied petroleum gas).

Air, or air plus residual combustion gases from the exhaust, known as exhaust gas recirculation (EGR), is introduced into the chamber during the intake stroke and compressed during the compression stroke in diesel engines. This raises the temperature of the air inside the cylinder to the point where atomized diesel fuel poured into the combustion chamber ignites. The fuel dispersion is uneven when it is introduced into the air right before combustion; this is known as a heterogeneous air-fuel mixture. The air-fuel ratio () is used to manage the torque produced by a diesel engine; rather of regulating the intake air, the diesel engine controls the amount of fuel injected, thus the air-fuel ratio is normally high.

Due to its extremely high expansion ratio and natural lean burn, which allows heat to be dissipated by extra air, the diesel engine has the best thermal efficiency (engine efficiency) of any practicable internal or external combustion engine. Because unburned fuel is not present during valve overlap, no fuel passes directly from the intake/injection to the exhaust, a slight efficiency loss is avoided when compared to non-direct-injection gasoline engines. Low-speed diesel engines (such as those used in ships and other applications where total engine weight is less of a concern) can achieve up to 55 percent effective efficiency. The combined cycle gas turbine (Brayton and Rankin cycle) is a more efficient combustion engine than a diesel engine, but it is unsuitable for automobiles, watercraft, or aircraft due to its mass and dimensions.

Diesel engines are available in two-stroke and four-stroke cycles. Originally, they were intended to be a more efficient alternative to stationary steam engines. They’ve been utilized in submarines and ships since the 1910s. Later applications included locomotives, buses, vehicles, heavy equipment, agricultural equipment, and power plants. They were first employed in a few autos in the 1930s. Diesel engines have been used in larger on-road and off-road vehicles in the United States since the 1970s. According to Konrad Reif (2012), diesel automobiles account for half of all newly registered cars in the EU.

14-cylinder, two-stroke marine diesel engines with a peak power of about 100 MW each are the world’s largest diesel engines in service.

What fuel do I use in a 4-stroke engine?

Clean, fresh, and free of lead. Minimum 87 octane/87 AKI (91 RON); see below if operating at high altitude. It is acceptable to use gasoline containing up to 10% ethanol (gasohol) or up to 15% MTBE (methyl tertiary butyl ether). Some gas stations currently sell gasoline containing up to 15% ethanol.

How are diesel and petrol engines different?

The diesel and gasoline engines found in most automobiles are very similar. They are, in essence, internal combustion engines with a two- or four-stroke cycle. The power cycle in an internal combustion engine consists of four phases: intake, compression, power, and exhaust.

The opening intake valve draws air into the cylinder during the intake phase. The intake valve closes during the compression phase, and air and gasoline are compressed together. The mixture of gasoline and air is ignited at this point, resulting in an explosion. The piston is driven downwards by this explosion, which drives the crankshaft to produce motion. This is the time when you have the most power. The spent air-fuel combination is blasted out of the cylinder by the opening exhaust valve in the final phase, allowing a fresh cycle to begin.

The major difference between diesel and gasoline engines is that gasoline engines utilize spark plugs to ignite the air-fuel mixture, whereas diesel engines rely entirely on compressed air. As previously stated, Rudolf Diesel discovered that by significantly compressing air, the temperature could be raised to a sufficient level. The temperature would climb to the point where it could cause diesel fuel to ignite.

As a result, in diesel engines, the air in the cylinder is compressed to roughly 14 to 23 times its original volume. Because petrol engines rely more on the spark plug to start the power phase, the compression ratio is typically significantly lower. Compression ratios in petrol engines are normally between 7 and 10, with high-performance automobiles having up to 13 compression ratios.

High compression ratios are advantageous because they increase thermal efficiency. In other words, the air-fuel mixture can be used for more energy. This also helps to explain why diesel engines are far more efficient than gasoline ones. In fact, of all internal combustion engines, diesel engines have the highest thermal efficiency.

The Pros and Cons

What other advantages do diesel engines have over gasoline engines, besides from being more efficient? What are the drawbacks of diesel engines? Let’s take a quick look at a few of the most crucial ones.


  • Diesel engines are not only more efficient, but diesel fuel is also less expensive. Diesel fuel is about 40% cheaper per liter than gasoline at the time of writing. This means diesel vehicles will be less expensive to operate, which is why most buses and taxis are powered by diesel engines.
  • Cars can get fantastic mileage out of diesel engines since they are so efficient. Passengers cars with modest 50 liter fuel tanks may easily drive over 1000 kilometers on a single tank. This means that you’ll spend more time traveling and less time refueling.
  • Diesel engines are built to endure the tremendous compression of gases within the cylinders and will normally survive longer than their petrol counterparts. They can also go longer without having to be serviced.
  • With minimal or no modifications, diesel engines can run on alternative and renewable fuels like biodiesel. Biodiesel is used vegetable oil that has been used for cooking that has been recycled and treated so that it may be used to fuel diesel vehicles.


  • Because diesel engines must be built tougher to resist the tremendous compression of gases, they are typically more expensive to produce. As a result, diesel cars can occasionally be more expensive than their gasoline counterparts. This is highly dependent on the manufacturer.
  • Diesel engines have a unique knocking sound known as diesel clatter. This sound is caused by a pressure wave caused by the quick igniting of gasoline. Diesel engines become less refined and noisier as a result of this.
  • Diesel engines are heavier and less willing to rev than gasoline engines, making them unsuitable for sports cars. Diesel automobiles are also less zippy and engaging to drive as a result of this.
  • Diesel cars in Singapore are subject to a specific charge on top of the standard road tax, which can increase the car’s operating costs. We’ll go through this tax in greater detail below because it can be rather high.

Special Tax

Diesel cars were once uncommon in Singapore, which is understandable given the industry’s poor reputation. Diesel cars are frequently regarded as polluting and slow, and a hefty special tax was imposed on them to make matters worse. Because there is no charge on diesel fuel, this particular tax is imposed on diesel vehicles. Petrol, on the other hand, is subject to a petrol charge, which, according to the LTA, fosters fuel conservation and discourages the excessive use of petrol cars, which can contribute to traffic congestion and pollution.

However, in the last ten years, things have altered tremendously. Diesel technology is quickly improving, and governments are realizing the environmental benefits of diesel vehicles and enacting regulations to encourage their use. As a result, diesel vehicle sales have increased. Diesel car sales are on level with or even exceeding those of gasoline cars in numerous European countries, including Austria, Belgium, and Germany.

Diesel automobile sales are increasing in Singapore, albeit slowly. Knowledgeable car buyers are now willing to try diesel, thanks in part to the government’s revision of the special tax on diesel vehicles. The special tax on modern diesel cars that fulfill Euro V requirements has been considerably cut. One only needs to look at the tax rates to see how much cheaper it is to drive a diesel car now.

The extra tax for a pre-Euro IV compliant car is a whopping 6 times the petrol equivalent road tax. To put it another way, if a 1600cc diesel car had a 6-month basic road tax of S$372, the special tax on a pre-Euro IV compliant diesel automobile would be a stunning S$2,232. The total tax for the six months would be S$2,604.

The extra tax for a Euro IV compliant car is determined at $0.625 per cc of engine capacity, with a minimum of S$625. This means that in addition to the S$372 regular road tax, we must pay an additional S$1000 special tax. As a result, the total road tax for 6 months would be S$1,372. It’s a lot less, but it’s still a big premium above a gasoline-powered automobile.

The special tax is determined at a lower rate of $0.20 per cc and is subject to a minimum of $200 if you bought a new diesel that is Euro V or JPN2009 compliant. This means that the special tax levied on a 1600cc diesel would be only S$320, lowering the total 6-month road tax to a far more reasonable and economical S$692.

Here’s a table that summarizes the various taxes due, using a 1600cc engine as a comparison.

This meant that, in the past, and with older diesel cars, you’d have to travel long distances to justify the special tax’s higher expenditures. However, thanks to lower tax rates, driving a diesel is now more economical and financially viable.

How often does a 4-stroke engine make power to turn the crankshaft?

Every second spin of the crankshaft, a 4-stroke engine ignites (every fourth stroke of the piston). The cycle is made up of four parts: induction (when the piston advances outwards from the cylinder head, the inlet valves open and the fuel/air mixture is admitted);

What does 4-stroke mean?

To simplify things, two-stroke motorbikes are no longer manufactured because they do not comply with many nations’ environmental rules and are not permitted to be driven in cities, and the dispute between the two types of engines is more relevant to off-road vehicles, such as dirt bikers.

A four-stroke engine, as the name implies, has a piston that completes one full cycle by going through four strokes (or two crankshaft revolutions): intake, compression, power, and exhaust. This means that when the piston descends from the top to the bottom of the cylinder, the pressure inside the cylinder decreases. Through the intake port, this reduced pressure draws a mixture of fuel and air into the cylinder. The piston then rises again, compressing the fuel and air combination before being ignited by a spark. The resultant combustion is what causes the piston to return to its original position in the “power stroke.” Finally, the piston returns to its original position and pushes the combustion gases out. Two-stroke engines work by combining multiple functions into a single piston movement; while the piston is moving upwards in the combustion chamber (compressing the air/fuel/oil mixture), a new combination of air/fuel/oil is being drawn into the hermetically closed crankcase beneath the piston. The fresh air/fuel/oil combination is compressed and fed through one or more flush ports to the combustion chamber during the downward movement of the piston (power stroke), flushing out the burnt gases through the exhaust port, which is opened by the downward movement of the piston. Following that, a new compression stroke is performed. A two-stroke engine requires one full crankshaft rotation or two piston strokes to complete one complete cycle, whereas a four-stroke engine requires the piston to complete four strokes or two full crankshaft revolutions.

So, which is the best option? This is entirely dependent on the rider’s own preferences. Two-stroke engines are often noisier and emit more exhaust fumes than four-stroke engines, but they also produce more power per pound of weight, making them popular for racing. While four-stroke engines are heavier and produce less power per unit of weight, they are said to operate smoother, release fewer exhaust pollutants, and last longer.

Because the two require completely different lubrication regimes, in which the oil is mixed with the fuel and then ignites (full loss of lubrication), whereas the oil used to lubricate the various engine parts flows back into the crankcase and is not burned in a four-stroke engine. This means that depending on their intended use, the two engine oils have radically different compositions. A two-stroke engine oil must mix properly with gasoline and burn efficiently in the combustion chamber, but a four-stroke engine oil must protect the valve train from wear and maintain the engine as clean as possible. Finally, a high-quality engine oil can considerably lengthen the life of your engine, regardless of the type of engine you have.

What is the difference between 4-stroke and 2?

The fundamental difference between a 4-stroke and a 2-stroke engine is that a 4-stroke engine completes one power stroke in four stages, or two complete revolutions, whereas a 2-stroke engine completes one power stroke in two stages, or one entire rotation. This means that a 2-stroke engine can possibly produce twice as much power and weigh half as much as a 4-stroke engine.

Stroke Engine

Four-stroke engines use less gasoline and are less harmful to the environment. They work in four stages:

  • Fuel is sucked in with a downward stroke through the intake valve, which is open.
  • The engine’s power is produced by igniting the compressed fuel once it has been compressed.

Stroke Engine

On the upstroke, the compression and ignition steps are combined, and on the downstroke, the power and exhaust steps are combined. This method uses fewer moving parts, making maintenance easier, but it produces less torque.

  • The piston rises, and air and fuel enter the crankcase on the upstroke (ignition/compression). The mixture of gasoline and air is compressed and ignited.
  • Downstroke (power/exhaust): The piston is pushed down and the exhaust is discharged after the fuel is ignited.

Both engine types have advantages and disadvantages, and which one will work best for you depends on your application’s requirements. Despite the fact that 4-stroke engines perform well and survive longer than 2-stroke engines, 2-stroke engines are lighter and faster.

How many cylinders does a 4-stroke engine have?

At any given time, a four-stroke engine with five or more cylinders can have at least one cylinder completing its power stroke. Four-cylinder engines, on the other hand, have gaps in the power delivery since each cylinder completes its power stroke before the next piston begins a new one. More vibrations are produced by this pulsing power supply than by engines with more than four cylinders.