Automobile Ignition System: Mechanism, Components and Working

A vehicle has many components which are crucial for its functioning. An automobile ignition system is one of them. All parts of an ignition system have to work in perfect sync, or your vehicle will not even start.

The following article will explore how ignition systems work in automobiles and its various types.

What Is an Automobile Ignition System?

An ignition system is used in internal combustion engines to create an electric spark in the engine combustion chamber to ignite a petrol and air mixture. It is an integral component of automobiles often treated as the sub-section of the engine-management system.

What Is the Function of Ignition Systems in Automobiles?

The main function of a vehicle's ignition system is to ignite the air-fuel mixture in its internal combustion engine. To do this, it creates a high-voltage spark using its spark plugs which makes a car fuel burn, causing its pistons to turn its wheels.

An automobile ignition system must work in tandem with all other parts of an engine. So, igniting the fuel at the right time is necessary to make a vehicle function smoothly. The timing of a high-voltage electric spark depends on a vehicle’s load, speed and other factors.

How Do Automobile Ignition Systems Work?

Listed below are basic points on how the ignition system works:

In a conventional ignition system, there are two main sets of windings/circuits—primary and secondary. The primary circuit works on battery current and is responsible for carrying low voltage. Some breaker points and an ignition switch control this primary circuit. When a driver turns on the ignition key of a vehicle, its battery supplies 12 volts of current to its ignition coil through the contact breaker points. This flow of current creates a magnetic field around this coil.
The secondary circuit is not electrically connected to the primary circuit. It has secondary windings in its coil and high tension lead between the distributor and coil wire on external coil distributors. Furthermore, it also consists of a distributor rotor, a distributor cap, spark plug leads and spark plugs. The engine's rotation turns the distributor shaft cam which separates the breaker points, which, in turn, stops the current flow. This leads to a collapse of the magnetic field around this coil.
When these contacts break, a high voltage current of 20,000-25,000 volts passes through the secondary winding. Then, the current flows through the high-tension cable and reaches the distributor cap, which moves along the drive shaft’s direction. Its movements are aligned with the high-tension cables corresponding to each spark plug. This alignment enables the cam lobes to open all contact points after each compression stroke of the cylinder. This lets the high-voltage current pass to the respective spark plug, ultimately creating a spark.

What Are the Components of an Automobile Ignition System?

Let us look at some important features in an automobile ignition system that creates a spark:

1. Spark Plug

Discussed below are important points related to this feature:

A spark plug is not difficult to understand. It enables high-voltage electricity to move across a gap and create a spark. The voltage at a spark plug can range from 40,000 to 100,000 volts.
Spark plugs need to have insulated passageways which would allow high-voltage electricity to reach the electrode. Moreover, a spark plug's design enables it to withstand heat and pressure inside the cylinder. It ensures that this spark plug does not accumulate deposits from fuel additives.
Generally, spark plugs use ceramic inserts to separate high-voltage electricity at the electrode. This material ensures that the spark takes place at the tip of the electrode only and not anywhere else.

2. Ignition System Coil

The ignition coil is a high-voltage transformer with two wires coils—primary and secondary coils. Given below are some important points about this part of the automobile ignition system:

It is the primary winding of a coil through which current first flows. Note that the current in a coil primary winding can face disruptions from breaker points.
For a simpler understanding, an ignition system coil resembles an electromagnet and functions as an inductor.
The primary coil's magnetic field collapses when the breaker points break the circuit. On the other hand, a strong magnetic field takes over the secondary coil and gives rise to a high-voltage current.
The secondary coil transfers this voltage to the distributor through a high-voltage and well-insulated wire.

3. Ignition System Distributor

Listed below are important points:

Its primary function is to distribute high-voltage electricity from the coil to the correct cylinder with the help of a cap and rotor. A rotor, spinning inside the cap, is connected to its ignition coil.
The secondary coil releases a high-voltage pulse every time the rotor comes in contact with the cylinders. This high-voltage pulse moves to the spark plug on the right cylinder.

What Are Different Types of Ignition Systems in Automobiles?

Now, let us look at various types of ignition systems in automobiles used in spark-ignition internal combustion engines. Generally, it can be categorised into three types:

Magneto ignition system
Electronic ignition system
Battery ignition system

As mentioned before, the main function of an ignition system is to facilitate an electric spark in the engine combustion chamber at the right time. Let us take a detailed look at how this works for different automobile ignition systems:

1. Magneto Ignition System

Listed below are important points:

A magneto is a small generator that runs on electricity. When an engine rotates the generator, it produces a voltage. In this ignition system, a magneto is responsible for creating high-voltage energy.
This high voltage, in turn, generates electricity that helps a vehicle run. For example, a distributor and a generator are built as a single unit in a magneto ignition system.

2. Electronic Ignition System

Here are the important points on this automobile ignition system:

It is entirely controlled electronically and is powered by a battery. As a result, it has negative and positive terminals.
The negative terminal remains grounded while the positive terminal is used to connect with the ignition switch. If it is on, power supply to the electronic ignition module takes place through the wires.
After that, an electronic ignition module transfers power to its ignition coil with two main windings—primary and secondary—which are insulated. Note that the thickness of its primary winding should be more than its secondary one.
An iron rod, located in between primary and secondary winding, creates a magnetic field. When the armature rotates, it produces power and connects with the electronic module. This results in magnetic pick-up.
The connection between magnetic pick-up and armature creates a voltage signal that transfers to a distributor with a rotor. The connection between rotors and distributor points transfers voltage to the high-tension cable. The resulting voltage difference between the central and ground electrodes creates a spark at the spark plug, resulting in combustion.

3. Battery Ignition System

Listed below are its essential points:

This ignition system primarily uses a 6 or 12-volt battery that the car engine-driven generator recharges.
Ignition coil present in this system is responsible for increasing its voltage while its distributors take charge of directing the current to each cylinder.
After this, the spark plug, which has a central electrode with an insulating ceramic around it, is responsible for projecting the current into each cylinder.

What Are the Advantages of Different Automobile Ignition Systems?

Detailed below are some advantages of the different types of ignition systems:

Magneto ignition systems require less maintenance and less space, and their associated costs are also low. In addition, the high-intensity spark results in high working efficiency.
A major advantage of an electronic ignition system is that it leads to increased fuel efficiency. Moreover, it generates less emission.
An important benefit of a battery ignition system is the high concentration and intensity of sparks.

What Are the Disadvantages of Different Automobile Ignition Systems?

Listed below are some disadvantages of different ignition systems:

When a vehicle starts, poor quality of spark is a major limitation of the magneto ignition system.
An electronic ignition system is associated with high expenses. Considering that the system needs a battery to function, it requires a lot of space.
Periodic maintenance of the battery and more storage space are limitations of a battery ignition system. In addition, if spark intensity decreases, its efficiency reduces.

FAQs About Automobile Ignitions System

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How long does an ignition coil last?

Generally, an ignition coil lasts for 100,000 miles or more. But there might be several reasons behind its premature damage. For instance, heat and moisture may cause damage to the copper wire inside the ignition coil.

What are the symptoms of a damaged ignition coil?

Difficulty in starting a vehicle’s engine and poor fuel economy are some of the symptoms of a faulty ignition coil. Moreover, if a car engine misfires or stalls, it indicates a problem with the ignition coil.