Car Engine Mechanics (An insight)

In this brief article we analyse the various components of a car engine, its working.We also learn the characteristics of different types of engines based on the type of fuel consumed. 

Car Engine Mechanics

Engines are the heart and soul of a car.In its bare essence engines are machines that convert the chemical energy to mechanical work.They burn fuel i.e gasoline(petrol),diesel ,natural gas etc and deliver power to run the car.Cars use Internal Combustion(IC) engines as their prime movers.

Modern car engines,whether petrol or diesel use what is known as 4 stroke cycle.The cycle is as follows
3.Expansion or Power.

Various Parts of a Car Engine

The car engine is a complex amalgamation of various mechanical parts that work in tandem to draw air and fuel into the combustion chamber, burn the mixture and then release it through the exhaust.This produces power which is transmitted to the gearbox and subsequently to the wheels thus providing traction to the car.
Some of the crucial engine components are:

Inlet and Exhaust Valves

The opening and closing of these valves,also known as poppet valves.regulate the flow of air-fuel mixture into the engine( only air in case of diesel engine) and also exhaust gases out of the engine;s combustion chamber. Their timings are crucial to the proper operation of the car engine.


The camshaft is that part which operates the valves.Its rotary motion opens the poppet valves.It is driven by the crankshaft generally through a chain.


The piston is perhaps the most important component in the car engine.It reciprocates within the cylinder causing the stroke of the engine.It is the reciprocatory motion of the piston that causes the rotation of the crankshaft.It is sealed within the engine cylinder by piston rings.These rings secure that the engine oil in the crankcase does not enter the combustion chamber.

Connecting Rod

The connecting rod of the engine serves as a link between the piston and the crankshaft.


The crankshaft is that part which rotates due to the reciprocatory action of the piston.It is generally located below the connecting rod and is placed within the oil sump.The action of the crankshaft also drives the camshaft. It is the power that is delivered by the crankshaft that is transferred to the transmission unit of the car.

Mechanism of Fuel Ignition

It depends on the type of fuel. While petrol engines use the Spark Ignition(S.I) method, diesel engines are ignited by the pressure of compression within the combustion chamber.
In the petrol engine,the air-fuel mixture is sent to the engine via a device called carburetor.In the diesel engine, the fuel is injected by a fuel injector and only air at the end of the compression cycle.

The Working of a 4-Stroke Engine

The Four Stroke Car Engine which uses petrol/gasoline or diesel as fuel intakes the air-fuel (air only for diesel engine) mixture through an inlet manifold and power is produced by 4 strokes of the piston as explained below.

1.Inlet stroke:

In this stroke,the inlet valve is opened and the piston moves from the Top Dead Centre(T.D.C) to the Bottom Dead Centre B.D.C) thus allowing for the air-fuel mixture to enter the cylinder.

2.Compression Stroke:

In this stroke, the piston moves from the BDC to TDC.This compresses the air-fuel(air only for diesel engine) mixture and prepares it for combustion.At the end of this stroke, a spark plug causes a spark which ignites the air-fuel mixture in case of a petrol engine whereas in diesel engines, a fuel injector injects diesel into the combustion chamber.

3.Power Stroke:

Due to the combustion of air-fuel mixture in the cylinder of the car engine, the piston moves from the T.D.C to B.D.C. 

4.Exhaust Stroke:

In this stroke, the piston moves back to T.D.C from the B.D.C and drives the exhaust gases away through the exhaust valves.

Spark ignition vs Compression Ignition Engine:

The most popular car engines available in the present automotive industry are those that run either on petrol or diesel.Petrol engines are also called as Spark Ignition engines as the ignition of the air fuel mixture in the combustion chamber occurs through sparking by a spark plug.On the other hand, diesel engines are called Compression Ignition engine as it does not have a separate ignition mechanism. In a C.I engine, the pressure of the air at the end of the compression stroke is high enough to cause ignition of the air-fuel mixture after injection.

Some of the key differences are:

1.Type of Fuel

Spark Ignition car engines use petrol as fuel, whereas Compression Ignition engines use diesel.

2.Fuel Intake Mechanism

Petrol car engines use the carburation to mix air and fuel which is then sent to the engine by the inlet manifold. Diesel engines on the other hand uses a fuel injector to spray the diesel into  the combustion chamber.


Petrol engines are known for their silent operation whereas diesel engines operate with high levels of noise and vibration compared to petrol engines.

4. Supercharging and Turbocharging

These are methods to increase the power output of engines by increasing the pressure of intake air.While Diesel engines are turbocharged and supercharged, petrol engine supercharging is not popular as its efficiency is lower.

5.Cold Starting.

Petrol engines are easier to cold-start than diesel engines.

Frequently Asked Questions (FAQs):Car Engine Mechanics

1.What are the most important engine parts?

Engines are complex machines and contain numerous parts.Some of the basic engine parts include piston, valves, crankshaft, connecting rod, camshaft, engine block etc.

2. What are the different types of car engines?

Based on the type of fuel used, car engines can be classified into petrol or diesel engines. Petrol engines are also called Spark Ignition(S.I) engines and Diesel Engines are called Compression Ignition engines.

3.What is the job of the car engine?

The most important function of the car engine is to deliver power in order to get the car moving.However, it also has other functions such as running the air conditioner (A/c).

4.What are some of the common engine problems?

Some of the common troubles associated with car engines are overheating, wear of parts, improper spark timing, knocking etc. Regular maintenance of the car by servicing can avoid these problems.

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