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Ignition systems
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- 3. IGNITION FUNCTION • Produces30,000 volt spark across spark plug • Distributes high voltage spark to each spark plug in correct sequence • Times the spark so it occurs as piston is nearing top dead center • Varies spark timing with load, speed, and other conditions
- 4. BASIC IGNITION SYSTEM COMPONENTS •BATTERY • IGNITION SWITCH • IGNITION COIL • SWITCHING DEVICE • SPARK PLUG • IGNITION SYSTEM WIRES
- 5. BASIC IGNITION SYSTEM • Batterysupplies power to entire system • Ignition Switch turns engine on or off • Coil transforms volts • Switching device triggers ignition coil • Spark Plug and wires distribute spark
- 6. PRIMARY CIRCUIT • Consistsof low voltage wiring and components • Uses conventional type automotive primary wires • Controls when ignition will take place. (When coil fires)
- 7. SECONDARY CIRCUIT • Distributescurrent to individual cylinders to jump spark plug gap • Must have thicker, heavier insulation on wires • Typical voltage to jump gap - 10K Volts
- 8. IGNITION COIL • TRANSFORMER •2 SETS OF WINDINGS – Primary windings – Secondary windings • IRON CORE • PRODUCES MAGNETIC FIELD
- 9. IGNITION SYSTEM TYPES •CONTACT POINT IGNITION SYSTEM • ELECTRONIC IGNITION SYSTEM • DISTRIBUTORLESS IGNITION SYSTEM
- 10. CONTACT POINT SYSTEM •Distributor turns 1/2 engine rpm • Distributor Cam • Contact Points • Condenser • Point Dwell (Cam angle) • Basis for all Systems
- 11. DWELL (CAM ANGLE) •Amount of time in distributor degrees that points remain closed between each opening • Coil saturation time is controlled by amount of dwell
- 12. ELECTRONIC IGNITION SYSTEM •Uses electronic control circuit to operate the ignition coil • More dependable than contact system • Higher secondary Ignition voltages
- 13. MAGNETIC PICK UPCOIL • Produces tiny voltage pulses to create magnetic field changes • Trigger Wheel interrupts magnetic field • Tell control unit (amplifier) when to fire ignition coil
- 14. HALL EFFECT DEVICE • HallEffect element is a solid state device • Contains a permanent magnet next to element • A Tab shunts magnetic field to send signal to control unit • Signal is On or Off
- 15. IGNITION CONTROL UNIT AMPLIFIER •Controls Primary current to tell Ignition Coil when to fire spark plugs
- 16. HIGH VOLTAGE SECONDARY COMPONENTS •IGNITION COIL • COIL WIRE • DISTRIBUTOR • DISTRIBUTOR CAP • DISTRIBUTOR ROTOR • SPARK PLUG WIRE • SPARK PLUG
- 17. SECONDARY CIRCUIT • DISTRIBUTESSPARK TO RIGHT PLACE AT RIGHT TIME • PARTS ARE DESIGNED TO CONTROL HIGH VOLTAGES
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- 19. 1 2 34 7 5 6 8 9 10 1.Normal 2.Overheated 3.Pre-ignition 4.Cracked insulator 5.Bridged gap 6.Deposit fouled 7.Carbon glazed 8.Splashed 9.Glazed 10. Oil fouled
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- 21. DISTRIBUTORLESS IGNITION • Timingis very precise • No mechanical parts to wear out • Requires less maintenance • Ignition timing is USUALLY not adjustable • Computer relies on ignition sensors • On-board computer controls ignition timing usually through a ignition module
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- 24. IGNITION TIMING FACTORS •Ignition timing is how early or late spark plugs fire in relation to position of engine pistons • Ignition timing must vary with engine speed, load and temperature • Must be advanced at times and retarded at other times
- 25. METHODS OF IGNITIONTIMING • DISTRIBUTOR CENTRIFUGAL ADVANCE • DISTRIBUTOR VACUUM ADVANCE • ELECTRONIC (COMPUTER) ADVANCE
- 29. IGNITION TIMING COMPENSATES FORBURN TIME
- 30. CENTRIFUGAL ADVANCE • VARIESIN DIRECT RELATION TO ENGINE RPM • CENTRIFUGAL FORCE THROWS WEIGHTS OUT • ALLOWS SPARK TO HAPPEN SOONER TO ALLOW ENOUGH TIME FOR COMBUSTION TO TAKE PLACE ON POWER STROKE. FIG 5-34
- 31. VACUUM ADVANCE • Provideadvance at lower engine speeds and part throttle operation • Matches timing to engine load • Controlled by venturi vacuum or manifold vacuum FIG 5-35
- 32. ELECTRONIC SPARK TIMING •Distributor does not have a centrifugal or vacuum advance mechanism • Uses engine sensors as inputs to computer • You must disable spark advance when setting base timing on computer controlled cars
- 34. ENGINE FIRING ORDER • REFERSTO SEQUENCE SPARK PLUGS FIRE • CAST INTO INTAKE MANIFOLD • EACH ENGINE WILL HAVE DIFFERENT FIRING ORDER • MUST USE DURING TUNE-UP FIG 5-3