Ignition Coils: Notes
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.