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Difference Between Petrol and Diesel Engine for JEE Main 2024

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Last updated date: 09th Apr 2024
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What are Petrol and Diesel Engines?

Car, trucks, bus and other automobiles run on engines based on fossil fuels. The two most common types of engine are petrol engine and diesel engine. Most of the vehicles run either on petrol engine or diesel engine. The main difference between the petrol engine and diesel engine is that in a petrol engine, fuel and air both are compressed with a spark, while in a diesel engine, only air is compressed, and fuel is injected in compressed air. Petrol engines and diesel engines work on the otto cycle and diesel cycle, respectively. 


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Petrol Engine

Petrol engines are mostly used in cars, scooters, machines, etc. It is an internal combustion engine with spark ignition. It is also known as a gasoline engine. It was 1st invented in Europe, 1876. It was a very basic model of the petrol engine. After this many improvisations have been done and the present model which people are using is the latest one. In petrol engines, air and fuel are mixed before compression and then an electric spark is used for ignition. Ignition temperature is the lowest temperature at which a fuel or combustible substance, when heated, catches fire. It works on the Otto cycle. Otto cycle explains how in gasoline engines, chemical energy is converted into thermal energy and then into motion.



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Petrol Engine 


How Does The Petrol Engine Work?

Working of petrol engine can be expressed by the following four steps shown in the image below.



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Working of a Petrol Engine

Step 1. Fuel (petrol) and air are added to the cylinder and mixed.

Step 2. The mixture of petrol and air is compressed by the use of a crankshaft.

Step 3. Now spark is used in the mixture and the mixture forces the piston down.

Step 4. Gases go out from the exhaust valve. 


Diesel Engine

Generally, trucks and other heavy vehicles run on diesel engines. It is also an internal combustion engine that works on diesel. In these engines, the air is compressed, so it becomes very hot and then fuel (diesel) is injected into it. Thus, diesel reaches its ignition temperature by the heat of compressed air. It is also known as a compression-ignition engine. It was 1st developed by Rudolf Diesel in 1893 in Germany. Diesel engines were mainly used in trains at that time.



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How Does a Diesel Engine Work?

A diesel engine works on a diesel cycle. It can be explained by the following steps shown in the figures below:



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Step 1. Induction Stroke ā€“ Piston of the engine goes down and air comes into the cylinder.

Step 2. Compression Stroke ā€“ Piston goes up and compresses the air. Now the air is getting hot. 

Step 3. Power Stroke ā€“ Now, fuel or diesel is added to the cylinder.

Step 4. Exhaust Stroke ā€“ Fuel or diesel starts burning due to ignition temperature provided by hot air. Smoke goes out from the valve.


Petrol Engine vs Diesel Engine

Diesel and petrol both are fossil fuels, but the working of petrol engines and diesel engines differ from each other. The difference between a petrol engine and a diesel engine can be explained by the following points.


Petrol vs Diesel Engine in Tabular Form

Petrol Engine

Diesel Engine

Petrol engine works on an otto cycle.

Diesel engines work on diesel engine cycle.

In this type of engine fuel and air mixture is compressed together.

In this type of engine fuel and air are not compressed together.

These engines work with highly volatile fuels.

These engines work with low volatile fuels.

In this type of engine ignition is induced by spark.

In this type of engine ignition is induced by heat generated by compression of air.

This engine has low compression ratios (7-10).

This engine has high compression ratios (11-20).

This engine has lower efficiency than a diesel engine.

This engine has higher efficiency than a petrol engine.

In this type of engine fuel consumption is higher.

In this type of engine fuel consumption is lower.

While working this engine makes less noise.

While working this engine makes more noise.

This engine has a high running cost.

This engine has low running cost.

It is mostly applicable for light duty applications.

It is mostly applicable for heavy duty applications.

In this type of engine, fuel and air are injected together.

In this type of engine, first air is injected and compressed, then fuel is added.

FAQs on Difference Between Petrol and Diesel Engine for JEE Main 2024

1.What is the primary difference between petrol and diesel engines?

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. 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.

2.Give the other name of the diesel engine.

Diesel engines are sometimes known as compression-ignition engines. They're also self-igniting engines. It's because, at the end of the compression stroke, the air compresses and gasoline injects into extremely hot air. As a result, the engine uses the heat of compression to start the ignition.

3.What are gasoline engines?

Petrol engines, as the name suggests, run on petrol, which we also refer to as gasoline. As a result, we also call them gasoline engines.