Car ignition coils
Powerful performance and precise ignition
How a Car Ignition Coil Works Principle of Operation The ignition coil acts like a transformer, stepping up the low voltage of the battery (12 V) to the thousands of volts needed to generate a spark in the spark plugs. When current flows through the primary winding, a magnetic field is created around the laminated iron core. When this flow is abruptly interrupted (by a transistor or mechanical breaker), the field collapses, and a very high voltage spike is induced in the secondary winding. This high-voltage pulse, directed at the spark plug, ionizes the air-fuel mixture and creates the spark that initiates combustion. Main Components Laminated iron core: Concentrates and amplifies the magnetic field generated by the primary winding. Primary winding: Thick wires (150–200 turns) that operate at 12 V and form the magnetic field. Secondary winding: Fine wires (2,500–3,000 turns) that receive the induced energy and reach 20,000–40,000 V. Housing and insulation: Protects the windings from heat, moisture, and electrical interference. Diagnosis and maintenance The coil suffers wear from heat and vibration. Failure symptoms include: Difficulty or inability to start Engine that “spurts” or vibrates at idle Increased fuel consumption Check engine light on with codes P0300–P0312 To check it, you can measure the resistance of the windings with a multimeter and observe the presence of spark at the spark plug during starting. The ignition coil is essential for engine performance and efficiency. Keeping it in good condition ensures reliable starts, complete combustion, and controlled emissions. Below we review the most notable brands, their history, and their main attributes. Bosch Origin: Germany With over a century in the automotive industry, Bosch stands out for its OEM-level reliability and advanced protection against corrosion and electromagnetic interference. Its coils typically include: Housings sealed with special polymers to resist water and salt. Electronic management that refines the primary pulse to optimize spark duration. Wide application range, from urban vehicles to high-performance engines. Denso Origin: Japan Denso is a first-party supplier to nearly all major Asian and European manufacturers. A pioneer in compact and modular coils, it leads the development of designs that integrate surge protection resistors and built-in diagnostic circuitry. Its units are highly regarded for: Excellent thermal response and cold-start stability. Low failure rate in high-vibration environments. Compatible with the latest generation coil-on-plug systems. NGK Origin: Japan Famous for its spark plugs, NGK also manufactures ignition coils that share its global reputation for quality. Its strengths are: Secondary coils with reinforced coating to better isolate high-voltage pulses. Large production volumes ensure immediate availability in workshops. Specific versions for turbo and direct injection engines, where spark control is more demanding. Delphi Origin: United States Delphi combines decades of experience in electronic systems with very complete replacement lines. Its coils incorporate: Control electronics that adjust the shape of the secondary waveform according to engine speed. Integration with knock sensors to prevent connecting rod knock. Coverage of American, European, and Asian models with a single catalog. Hella Origin: Germany Hella is distinguished by offering lightweight coils with high-strength polymer housings. Among its advantages are: Reduced weight to reduce dynamic loads on the engine. Plug & play options that facilitate replacement in fleets and commercial vehicles. Electromagnetic compatibility (EMC) certifications to avoid interfering with the vehicle's electronics. Continental Origin: Germany A long-standing specialist in ignition systems, Beru (part of Continental) manufactures coils that combine: A ferrite core optimized for stronger magnetic fields. Stabilized internal resistance for a uniform pulse at any temperature. Direct integration into timing modules for V6/V8 engines. Magneti Marelli Origin: Italy A regular supplier to Ferrari, Alfa Romeo, and other FCA Group brands, Magneti Marelli offers: Coils designed for high firing rates (up to 10,000 rpm). Special insulation that reduces energy loss in hard alloy spark plugs. Versions for motorcycles and scooters, as well as passenger cars. When replacing ignition coils, it is best to prioritize OEM compatibility or equivalents from reputable manufacturers. Factors such as winding precision, insulation, control electronics, and resistance to adverse conditions (temperature, vibration, humidity) determine the engine's lifespan and performance.
