Electronic Ignition System – types, Advantages of EIS

Introduction:

• Although the conventional mechanical contact breaker point type electrical ignition system has been very common in use because of its simplicity, yet due to its drawbacks and limitations the same is being fast replaced by the electronic ignition system.
• By the early 1970s, most automotive engines using a contact-point distributor could not meet exhaust-emission standards.
• Contact points cannot do this. They burn and wear during normal operation.
• This changes the point gap, which changes ignition timing and reduces spark energy, thus necessitating their servicing and resetting at smaller periods.

TYPES OF ELECTRONIC IGNITION SYSTEM

Electronic Ignition System is as follow :
(a) Capacitance Discharge Ignition system
(b) Transistorized system
(c) Piezo-electric Ignition system
(d) The Texaco Ignition system

Capacitance Discharge Ignition System
It mainly consists of 6-12 V battery, ignition switch, DC to DC convertor, charging resistance, tank capacitor, Silicon Controlled Rectifier (SCR), SCR-triggering device, step up transformer, spark plugs. A 6-12 volt battery is connected to DC to DC converter i.e. power circuit through the ignition switch, which is designed to give or increase the voltage to 250-350 volts. This high voltage is used to charge the tank capacitor (or condenser) to this voltage through the charging resistance. The charging resistance is also so designed that it controls the required current in the SCR.

Depending upon the engine firing order, whenever the SCR triggering device, sends a pulse, then the current flowing through the primary winding is stopped.
And the magnetic field begins to collapse. This collapsing magnetic field will induce or step up high voltage current in the secondary, which while jumping the
spark plug gap produces the spark, and the charge of air fuel mixture is ignited.

Piezo-electric Ignition System
The development of synthetic piezo-electric materials producing about 22 kV by mechanical loading of a small crystal resulted in some ignition systems for single cylinder engines. But due to difficulties of high mechanical loading need of the order of 500 kg timely control and ability to produce sufficient voltage, these systems have not been able to come up.

The Texaco Ignition System
Due to the increased emphasis on exhaust emission control, there has been a sudden interest in exhaust gas recirculation systems and lean fuel-air mixtures.
To avoid the problems of burning of lean mixtures, the Texaco Ignition system has been developed. It provides a spark of controlled duration which means that the
spark duration in crank angle degrees can be made constant at all engine speeds. It is a AC system. This system consists of three basic units, a power unit, a control
unit and a distributor sensor.

ADVANTAGES OF ELECTRONIC IGNITION SYSTEM

Following are the advantages of electronic ignition system :
(a) Moving parts are absent-so no maintenance.
(b) Contact breaker points are absent-so no arcing.
(c) Spark plug life increases by 50% and they can be used for about 60000 km without any problem.
(d) Better combustion in combustion chamber, about 90-95% of air fuel mixture is burnt compared with 70-75% with conventional ignition system.
(e) More power output.
(f) More fuel efficiency.