How an Ignition Coil Works: A Comprehensive Guide

The Science Behind Ignition Coils: How An Ignition Coil Works to produce 40,000 volts from a 12-volt input

An ignition coil is responsible for creating the high voltage needed to jump the spark plug gap and ignite the air-fuel mixtures. This article delves into the principles of operation, the design of ignition coils, and their role in modern automotive engines.

An Ignition Coil Creates High Voltage Through Magnetic Induction

The ignition coil is essentially a type of transformer, consisting of two coils of wire known as the primary winding and the secondary winding, wrapped around a laminated iron core.

The Primary Circuit Creates An Electro Magnet

The primary winding of the ignition coil is made up of relatively few turns of heavy-gauge wire wound around an iron core. It is connected to the car’s battery and the ignition switch. When the ignition switch is turned on, electrical current flows through the primary winding, creating a magnetic field around the coil. This magnetic field is the key to the coil’s operation.

The Secondary Circuit Converts The Collapsing Magnet Field into High Voltage

The secondary winding consists of many thousands of turns of fine-gauge wire and is connected to the spark plugs via the distributor (in older systems) or directly in modern coil-on-plug systems. The number of turns in the secondary winding is much higher than in the primary winding, which is essential for increasing the voltage.

How an Ignition Coil Works:

The ignition system is responsible for applying power and disconnecting power to the primary circuit. When the ignition system opens the circuit powering the primary circuit, the magnetic field around the primary winding collapses rapidly. This sudden collapse induces a high voltage in the secondary winding through electromagnetic induction. The voltage generated is proportional to the ratio of the number of turns in the secondary winding to the number of turns in the primary winding, which is why the secondary winding has so many more turns.

The high voltage generated in the secondary winding is then sent to the spark plugs. The spark plug gap acts as a barrier that the high voltage must overcome, creating a spark that ignites the air-fuel mixture.

Primary windings and the iron core

The primary winding consists of approximately 200 wraps of a thick gauge wire wound around an iron core. When 12 volts are applied to the primary windings, the primary winding creates a magnetic field, turning the unit into a powerful electromagnet.

Secondary windings

The secondary windings consist of approximately 20,000 wraps of small gauge wire wound around the primary windings and iron core.

See this post for information on bad ignition coil symptoms

See this post for information on how to test an ignition coil

How often does the ignition coil generate a spark?

The spark count per coil varies based on the type of ignition system. In a single coil (canister) ignition system, the formula to determine spark counts is:

Spark count = RPM x Number of cylinders÷2

For example: At 3,000 RPM on a 4-cylinder engine (3,000 x 4 ÷ 2) = 6,000 sparks per minute.

©, 2020 Rick Muscoplat