The three essential elements of a gasoline engine aregood air-fuel mixture, good compression, and good spark. The ignition system generates a powerful spark through proper ignition timing in order to ignite the air-fuel mixture.
1. Powerful sparks
In the ignition system, sparks are generated between the electrodes of the spark plugs to burn the air-fuel mixture. Because even air has electrical resistance, when it is compressed highly, tens of thousands of volts must be generated to ensure the generation of powerful sparks that can ignite the air-fuel mixture.
2. Proper ignition timing
The ignition system must provide proper ignition timing at all times to accommodate the changes in engine speed and load.
3. Sufficient durability
The ignition system must be able to provide sufficient reliability to withstand the vibrations and heat that are generated by the engine.
The ignition system uses the high voltage that is generated by the ignition coil to produce sparks, which ignite the airfuel mixture that has been compressed. The air-fuel mixture is compressed and burns in the cylinder. This combustion generates the motive force of the engine. Through self-induction and mutual induction, the coil generates the high voltage that is necessary for ignition. The primary coil generates several hundred volts and the secondary coil generates tens of thousands of volts.
Changes in Ignition Systems
The types of ignition systems are as follows:
1. Breaker points type
This type of ignition system has the most basic construction. With this type, the primary current and ignition timing are mechanically controlled. The primary current of the ignition coil is controlled to flow intermittently through the breaker points. The governor advancer and the vacuum advancer control the ignition timing. The distributor distributes the high voltage that is generated by the secondary coil to the spark plugs.
HINT
In this type, the breaker points must be regularly adjusted or replaced. An external resistor is used for reducing the number of windings of the primary coil, improving the rise of the primary current, and minimizing the reduction in the secondary voltage at high speeds. Reducing the number of windings of the primary coil reduces resistance, increases the primary current, and increases the generation of heat. For this reason, an external resistor is provided to prevent the primary current from increasing excessively.
2. Transistorized type
In this type, the transistor controls the primary current so that it flows intermittently in accordance with the electric signals that are generated by the signal generator. Timing advance is controlled mechanically in the same way as in the breaker points type system.
3. Transistorized type with ESA
(Electronic Spark Advance)
The use of the mechanical vacuum advancer and the governor advancer has been discontinued in this type. Instead, the ESA function of the engine ECU controls the ignition timing.
4. DIS (Direct Ignition System)
Instead of a distributor, this type employs multiple ignition coils to supply high voltage directly to the spark plugs. The ignition timing is controlled by the ESA function of the engine ECU. This system is predominant in recent gasoline engines.
HINT
Type 2 ignites two cylinders simultaneously. One spark occurs in the compression stroke and the other in the exhaust stroke.