How Does an Automotive Ignition System Work?
3 Answers
When a gasoline engine operates, the combustion of the air-fuel mixture is controlled by the spark plug ignition. The working principle of the ignition system is to supply the spark plug with high-voltage electricity of sufficient energy at the appropriate moment, according to the engine's operating state and sequence, causing a spark between its electrodes to ensure the ignition of the air-fuel mixture and enable the engine to perform work. The ignition process of the ignition system can be divided into the following three stages: Stage 1: Contact closure, formation and growth of the primary current. When the contacts are closed, a low current flows through the circuit, following this path: positive terminal of the battery - ignition switch - primary winding of the ignition coil - breaker contacts - negative terminal of the battery. Stage 2: Contact opening, generation of the secondary high-voltage stage. At the instant the breaker contacts open, the distributor rotor aligns precisely with one of the side electrodes. The current path at this stage is: secondary winding of the ignition coil - positive terminal of the battery - side electrode of the spark plug - center electrode of the spark plug - high-voltage wire - side electrode of the distributor - center electrode of the distributor - secondary winding of the ignition coil. Stage 3: Spark plug discharge stage. After the spark plug is energized, a discharge spark occurs between its center electrode and side electrode, igniting the atomized gasoline under compression in the cylinder, thereby activating the engine.
The ignition system is the key component that allows the engine to start. Its working principle begins with the battery supplying power: the battery provides low-voltage electricity, which is transmitted to the ignition coil. The coil, designed with a primary and a secondary winding, generates a high-voltage pulse when the current is interrupted. This pulse is sent through wires to the spark plugs in each cylinder. The spark plugs create a small arc inside the cylinder, igniting the mixture of air and gasoline, which produces an explosion that drives the piston. The entire process is controlled by the engine's computer to ensure ignition at the correct piston position. If the timing is off, the engine may shake, be hard to start, or consume more fuel, especially during cold starts in winter. Therefore, regular checks of the spark plugs and coil can prevent malfunctions.
Over the years of driving, the ignition system has taught me many lessons. At its core, it works by using the ignition coil to boost the battery's low voltage to a high voltage, which can reach up to around 20,000 volts, and then distributing it to the spark plugs. The spark plugs ignite the air-fuel mixture inside the cylinders, which is the source of the engine's power. Older cars relied on mechanical distributors to control the firing order of each cylinder, but newer cars use electronic control units that automatically adjust the timing based on engine speed and temperature. This improves reliability; if ignition is delayed, the car may experience poor acceleration or knocking; if ignition occurs too early, it might cause backfiring. So during routine maintenance, I always check the spark plug gaps and the condition of the wires to avoid breakdowns on the road. This is crucial for both driving safety and fuel efficiency.
