Ignition system

Objective

1. Identify the major components of an ignition system

2. Explain the function of each ignition system component

ALL ABOUT IGNITION SYSTEM

An ignition system in an automobile is a crucial component that initiates the combustion process in the engine. Its primary function is to generate a spark that ignites the air-fuel mixture within the engine's cylinders, enabling the engine to produce power.

Main Components of the Ignition System

1. Ignition Coil

The ignition coil functions as a step-up transformer. It converts the vehicle’s 12-volt battery current into a much higher voltage (ranging from 12,000 to over 45,000 volts) required to create an arc across the spark plug gap (Erjavec & Thompson, 2015). The coil consists of two windings—primary and secondary—and works on the principle of electromagnetic induction.

2. Spark Plug

The spark plug is the endpoint of the ignition system where the actual spark is produced. This spark ignites the compressed air-fuel mixture inside the cylinder. Spark plugs must be durable enough to withstand extreme temperatures and pressures, and they must be properly gapped to ensure consistent performance (Delgado & Stockel, 2020).

3. Distributor (in conventional systems)

The distributor is responsible for directing the high-voltage current from the ignition coil to the correct cylinder at the correct time. It typically contains a rotating rotor, cap, breaker points, and a condenser. Timing is mechanically set and synchronized with the engine crankshaft. However, modern systems have largely replaced distributors with more reliable electronic modules (Erjavec & Thompson, 2015).

4. Ignition Switch

The ignition switch is the driver’s interface with the system. When the key is turned or the start button is pressed, the switch closes the circuit that powers the ignition coil and other engine systems. If this switch fails, the vehicle may not start or may lose power during operation (AutoZone, n.d.).

5. Crankshaft and Camshaft Position Sensors

In electronic and distributor-less systems, crankshaft and camshaft position sensors provide real-time information about the engine’s rotation and piston position. This data is sent to the Engine Control Unit (ECU), which determines the optimal timing for spark delivery (Monolithic Power Systems, 2020). These sensors are critical for accurate ignition timing, especially in variable valve timing engines.

6. Ignition Control Module (ICM) / ECU

The ignition control module or engine control unit (ECU) replaces mechanical timing in modern systems. It receives signals from various sensors and manages the ignition timing electronically, improving fuel efficiency, power output, and emission control (Delgado & Stockel, 2020).

SUMMARY

The ignition system is a vital component of a vehicle's internal combustion engine, responsible for initiating the combustion process by producing a high-voltage spark. This spark ignites the air-fuel mixture in the engine cylinders, enabling the engine to generate power. Key parts of the ignition system include the ignition coil, which steps up the battery’s low voltage to the high voltage needed for ignition; the spark plug, which delivers the spark to the combustion chamber; and, in older systems, the distributor, which directs the spark to the correct cylinder. The ignition switch initiates the process when the driver turns the key or presses the start button. Modern ignition systems often rely on crankshaft and camshaft position sensors and electronic control units (ECUs) to determine precise spark timing, improving performance and reducing emissions. Types of ignition systems range from traditional mechanical systems to advanced electronic setups like Coil-On-Plug (COP), Distributor-less Ignition Systems (DIS), and Capacitive Discharge Ignition (CDI). As technology evolves, ignition systems have become more reliable and efficient, requiring less maintenance while enhancing engine operation (Delgado & Stockel, 2020; Erjavec & Thompson, 2015).

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