Modern Ignition System:
Modern ignition systems use electronic circuits. The ability of a transistor to interrupt a circuit carrying a relatively high current makes it an ideal replacement for the breaker points and condenser.
In modern automobiles the following two types are in common use.
(i) Transistorized coil ignition system (TCI system)
(ii) Capacitive discharge ignition system (CDI system)
Transistorized Coil Ignition (TCI) System:
In automotive applications, the transistorized coil ignition systems which provide a higher output voltage and use electronic triggering to maintain the required timing are fast replacing the conventional ignition systems. These systems are also called high energy electronic ignition systems.
When the transistor is ON, current passes through the primary side of the ignition coil (coil hereinafter) from the battery to store the energy. And when the transistor is OFF, the current is shut off causing a sudden change in the current, generating high voltage on the secondary side of the coil and initiating ignition
Advantages:
(i) reduced ignition system maintenance
(ii) reduced wear of the components
(iii) increased reliability
(iv) extended spark plug life
(v) improved ignition of lean mixtures
In transistorized coil ignition system, the contact breaker and the cam assembly of the conventional ignition system are replaced by a magnetic pulse generating system which detects the distributor shaft position and sends electrical pulse to an electronic control module.
Features:
- Ignition is possible even without a battery connection.
- Built-in electrolytic capacitor for kick-start.
- Compatible with all types of control, such as ignition and vehicle load controlled by onboard CPU.
Capacitive discharge ignition system (CDI system):
The capacitive discharge ignition system, a capacitor rather than an induction coil is used to store the ignition energy. The capacitance and charging voltage of the capacitor determine the amount of stored energy. Ignition transformer steps up the primary volt-age generated at the time of spark by the discharge of the capacitor through the thyristor to the high voltage required at the spark plug.
The capacitor is charged via a direct connection with voltage from the ACG or the battery, or the voltage is increased to charge the capacitor. The charged electrical load is discharged all at once, generating a high voltage on the secondary side of the coil, initiating ignition and combustion.
The advantage of using this system is that it is insensitive to electrical shunts resulting from spark plug fouling. Because of the fast capacitive discharge, the spark is strong but short (0.1 to 0.3 ms) which leads to ignition failure during lean mixture operating conditions. This is the main disadvantage of the CDI system.
Features:
- Ignition is possible even without a battery connection.
- Stable ignition is possible up to high RPM range.
- Built-in electrolytic capacitor for kick-start.
- Compatible with all types of control, such as ignition and vehicle load controlled by onboard CPU.
- Using our own step-up transformers, diodes and thyristors to offer high reliability at a low cost.
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