Diesel engine and gasoline engine are two types of internal combustion engine used in vehicles such as automobiles, motorcycles, motorboats, and aircraft, as well as small engines found in lawn mowers, chainsaws, and compact engine generators.
In buying an automotive vehicle, the type of engine plays a critical factor. Hence, it is important to understand the difference between diesel engine and gasoline engine due to cost considerations, performance aspects, and upkeep or maintenance, among others.
Diesel Engine vs Gasoline Engine: What is the Difference?
1. Ignition Mechanism
One of the primary difference between a diesel and petrol or gasoline engine is the mechanism for igniting the fuel. Note that both are internal combustion engines in which combustion occurs within an oxidizer or air in a combustion chamber.
In a diesel engine, the air gets compressed significantly during the compression stroke. This compression increases the temperature of the air very high. The fuel then undergoes combustion when it is injected into this hot and high-pressure environment.
A gasoline engine, on the other hand, requires an ignition-initiating apparatus like a spark plug to ignite the fuel and start a combustion. The spark produces a high voltage current that may be provided by a high-tension magneto or ignition coil.
It is also worth mentioning that a diesel engine is a type of compression-ignition engine while a gasoline engine is also called a spark-ignition engine.
2. Type of Fuel Used
Another main difference between a diesel engine and a gasoline engine is the type of fuel used. A diesel engine essentially uses a diesel fuel while a gasoline engine uses petrol or gasoline fuel.
There are specific differences between diesel fuel and gasoline. The first is that diesel has a higher energy density. To be precise, it contains about 15 percent more energy by volume than gasoline. This is the reason why a diesel engine is more energy efficient than a gasoline engine.
Note that diesel fuel contains more carbon atoms in longer chains than gasoline, thus making it more energy dense. Because of the same chemistry, diesel is also heavier and oilier, and it evaporates more slowly than gasoline.
Another difference between the two is emission. Diesel emits smaller amounts of carbon dioxide, carbon monoxide, and hydrocarbons than gasoline. However, it produces higher amounts of nitrogen compounds and soot or particulate matter.
3. Fuel Injection
Fuel injection is simply the process of direct introduction of fuel under pressure into the combustion chamber of an internal combustion engine. Diesel and gasoline engines use different fuel injection process.
A diesel engine uses direct fuel injection. This involves injecting a fine mist of fuel into the cylinder at the end of the compression stroke when the air is highly compressed and very hot. The high temperature of the compressed air ignites the fuel and causes a combustion.
Gasoline engine uses either direct injection or indirect injection. The direct injection process is similar to diesel engine but requires a spark plug to ignite the gasoline fuel. However, in indirect injection, the fuel is mixed with air during the intake stroke before it enters the cylinder.
4. Horsepower vs Torque
A horsepower is a unit of measurement of the power of an engine. On the other hand, torque is a measure of the twisting force of an engine on the driveline that causes an object to rotate. Diesel engines produce higher torque while gasoline engines have a higher horsepower and RPM.
Vehicles with diesel engines struggle to compete with their counterparts running on gasoline engines in terms of horsepower and acceleration. But these diesel-powered vehicles are still better at moving larger objects than their gasoline counterparts because diesel engines produce higher torque. This is the reason why trucks and heavy vehicles run on diesel.
There are several reasons why a diesel engine produces higher torque. These include higher compression ratio than a gasoline engine, spontaneous combustion without the need for a spark plug, longer stroke needed to compress more air, and the higher energy density of diesel fuel than petrol or gasoline fuel.
On the other hand, in terms of acceleration, a gasoline engine accelerates faster than a diesel engine because it is mechanically or physically lighter. A diesel engine is usually larger, more complex, and more durable to withstand high pressure and temperature.
Additional reasons why acceleration is faster in gasoline engine include shorter stroke length that can rev at higher rotations per minute, and the nature of the petrol or gasoline fuel, which burns and produces energy faster than diesel fuel.
5. Other Key Differences
There are other differences between diesel engine and gasoline engine. These include costs, reliability, pollution, and noise.
In terms of costs, diesel vehicles have higher entry prices due to the interplay between supply and demand. These vehicles can cost several thousand dollars more than gasoline-powered vehicles.
The maintenance costs of the two engines can relatively be the same. However, diesel engines are more durable but repairing them due to poor maintenance can be costlier due to more expensive mechanical parts.
Fuel cost is also important to take into consideration. In some countries, diesel fuel is 15 to 20 percent cheaper than gasoline. However, in countries where diesel vehicles are popular, diesel fuel has the same price as gasoline. There are also areas in which diesel are more expensive than gasoline due to high demands.
A diesel engine has been traditionally labeled as more polluting than gasoline engine because it produces particulate matters or snoot. However, when burned, diesel fuel produces lower carbon dioxide, carbon monoxide, and hydrocarbons than gasoline fuel.
Developments in engine technology and diesel fuel processing have made diesel engine considerably clean. However, when compared to a gasoline engine, it produces a significantly higher degree of noise pollution.
A Note on the Similarities Between Diesel Engine and Gasoline Engine
Remember that both diesel engine and petrol or gasoline engine are internal combustion engines. Their general working principles are similar. They are both based on the four-stroke process: intake, compression, combustion, and exhaust.
In addition, both engines are designed to utilize the chemical energy available in fuel and convert it to mechanical energy needed for the up-and-down motion of the pistons inside cylinders. The up and down movement of the piston creates the rotation needed to turn the wheels of a vehicle.
Both diesel and gasoline engines essentially convert the chemical energy in fuel into mechanical energy through combustion by ignition. In conclusion, the major difference between the two centers on how they produce combustion.
It is also worth mentioning that diesel engines have advantages or benefits than gasoline engine, although they also have drawbacks, limitations, and issues. The same is true for petrol or gasoline engines.
