Ignition Coil: Description and Operation

Ignition Coils
The high voltage supply required to ignite the mixture in the combustion chambers is determined by the stored energy in the ignition coils. The stored energy contributes to the ignition duration, ignition current and rate of high voltage increase. The Coil circuit including primary and secondary components consists of:

- Coil Assembly
- Primary Winding
- Secondary Winding
- Resistor
- Spark Plug
- EMS2000 Final Stage Transistor

The Coil Assembly contains two copper windings insulated from each other. One winding is the primary winding, formed by a few turns of thick wire. The secondary winding is formed by a great many turns of thin wire.

The primary coil winding receives battery voltage from the Main Relay which is activated by the EMS2000. The EMS2000 provides a ground path for the primary coil (Terminal 1) by activating a Final Stage transistor. The length of time that current flows through the primary winding is the "dwell" which allows the coil to "saturate" or build up a magnetic field. After this storage process, the EMS2000 will interrupt the primary circuit at the point of ignition by deactivating the Final Stage transistor. The magnetic field built up within the primary winding collapses and induces the ignition voltage in the secondary winding.

The voltage generated in the secondary is capable of 40,000 volts (40KV). The high voltage is discharged through the secondary ignition spark plug connectors.

EMS2000 uses a dual output coil which provides voltage to fire two plugs simultaneously. Spark delivered to one cylinder is wasted as the cylinder is on the exhaust stroke and two of the components of cylinder combustion are missing, fuel and compression. Little or no resistance to the spark movement is provided thus the voltage consumed during the waste spark firing is very low.

Spark delivered to the other cylinder provides the ignition for power generation. The cylinder is on the firing stroke, fuel is in the cylinder and cylinder pressures are high. The spark has a higher resistance and requires greater KV's to jump the plug gap.


Function
In the case of static high-tension ignition distribution, two ignition coils are fitted in one module. Each of these ignition coils has two secondary voltage outputs and thus supplies the ignition voltage for two cylinders. The coils work according to the ignition redundancy principle, which means that ignition takes place in these two cylinders at the same time. One spark plug ignites during the compression stroke and the other during the throw-out stroke.

Installation location
The ignition coils are located in the middle of the cylinder head.

Failure
If one coil fails, either the motor cannot be started or poor idling characteristics are the consequence. The misfires can cause the MIL to light up.
light up.