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Spark Plugs Chapter 1 Outline 08 From the following statements about ignition system, select the incorrect one. Both gasoline engines and diesel engines require spark plugs to ignite the air-fuel mixture. The ignition timing is adjusted according to changes in the engine speed and load. The air-fuel mixture for gasoline engines is the proportion of air and gasoline by weight and about 15:1 is called the stoichiometric air-fuel ratio. The spark voltage for spark plugs is generated when the primary current through the igniter is cut off. 4-cycle engines ignite and combust each cylinder one time for two rotations for the engine crankshaft. Answer on next page Contact Ignition Type (Ordinary Ignition Type) Transistor Ignition Type Electronic Spark Advance (ESA, DLI) Comprehensive Test Types of Ignition System Structurally, ignition system can be classified into the following three types. In this system, the current (primary current) flowing to the ignition coil from the battery is cut off at the mechanical contacts (breaker points) in the distributer to generate high voltage. Demerit Since these are mechanical contacts, sparks can fly between the contacts or the voltage drops at low speed. Also, sometimes current does not flow adequately due to soiling of the contact surface. This system generates high voltage by cutting off the current with transistors in the igniter. This system can provide stable high voltage. Demerit The ignition timing is controlled by the signal generator in the distributor, so there are limits to fine control. The ignition timing and dwell angle are controlled by microcomputer, which sends the ignition signals to the igniter, where the transistors inside the igniter cut off the current and generate high voltage. This makes more precise control possible and is the current mainstream ignition system. Battery 1 Ignition switch 2 Ignition coil 3 Breaker point 4 Distributor 5 Rotor 6 Spark plug 7 Battery 1 Ignition switch 2 Coil with an igniter 3 Signal generator 4 Distributor 5 Rotor Spark plug Distributor ECU Igniter Ignition Ignition Engine speed .NE Ignition signal IGt IGf Crankshaft position detection .G Sensors Air flow sensor Water temperature sensor Air conditioner signal etc 1 2 3 4 5 6 7 Ignition timing control Dwell angle control Constant-current control Dwell angle reduction Types of Ignition System Electronic ignition type (ESA:Electronic Spark Advance, DLI:Distributorless Ignition) Ignition monitor signal Comprehensive Test 4 5
