IGNITION COILS

Hytec Automotive ignition coils feature advanced engineering technology high-quality steel cores with optimized winding, resistance, and turn ratios to deliver 10-15 percent more energy than OEM coils. They are designed as a direct plug OEM replacement part. Their specialized high-temperature epoxy resists shock and vibration while increasing thermal conductivity. They feature bodies and/or secondary towers and brass secondary contacts (except direct fire coil on plug applications).

An ignition coil consists of a laminated iron core surrounded by two coils of copper wire. Unlike a power transformer, an ignition coil has an open magnetic circuit – the iron core does not form a closed loop around the windings. The energy stored in the core’s magnetic field is transferred to the spark plug. The primary winding has relatively few turns of heavy wire. The secondary winding consists of thousands of turns of smaller wires, protected to the high voltage by enamel on the wires and oiled paper insulation layers. The coil is usually inserted into a metal can or plastic case with insulated terminals for high and low voltage connections. When the contact breaker closes, it allows a current from the battery to build up in the primary winding of the ignition coil, and it does not flow instantly because of the coil inductance.

Current flowing in the coil produces a magnetic field in the core and the air surrounding it. The current must flow long enough to store enough energy in the field for the spark. The contact breaker opens once the current has built up to its full. Since it has a capacitor connected across it, the primary winding and the capacitor form a tuned circuit, so, as the stored energy oscillates between the inductor formed by the coil and the capacitor, the changing magnetic field in the coil core induces a much larger voltage in the secondary of the coil. The amount of energy in the spark required to ignite the air-fuel mixture varies based on the mixture pressure, composition, and engine speed.

Initially, every ignition coil system required mechanical contact breaker points and a capacitor. More recent electronic ignition systems, such as Hytec Automotive products, use a power transistor to supply pulses to the ignition coil. A modern passenger automobile may use one ignition coil for each engine cylinder (or pair of cylinders), eliminating fault-prone spark plug cables and a distributor to route the high voltage pulses. Ignition systems are not required for diesel engines, which rely on compression to ignite the fuel/air mixture.

In modern systems, the distributor is omitted, and ignition is electronically controlled. Much smaller coils are used with one coil for each spark plug or two spark plugs (for example, two coils in a four-cylinder engine or three coils in a six-cylinder engine). A large ignition coil puts out about 20 kV, and a small one -i.e., from a lawn mower- puts out about 15 kV. These coils may be remotely mounted or placed on top of the spark plug.

One coil serves two spark plugs (in two cylinders) through the “wasted spark” system. The coil generates two sparks per cycle to both cylinders in this arrangement. The fuel in the cylinder nearing the end of its compression stroke is ignited, whereas the spark in its companion nearing the end of its exhaust stroke has no effect. The wasted spark system is more reliable than a single coil system with a distributor and less expensive than coil-on-plug.