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34 Chapter Ignition System Technology. 34 Chapter Ignition System Technology.

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Presentation on theme: "34 Chapter Ignition System Technology. 34 Chapter Ignition System Technology."— Presentation transcript:

1

2 34 Chapter Ignition System Technology

3 Objectives After studying this chapter, you will be able to:
Explain the operating principles of any type of automotive ignition system. Sketch the primary and secondary circuits of an ignition system. Identify and describe the function of major ignition system components.

4 Objectives Describe the purpose of secondary wires in an ignition system. Compare ignition coil, spark plug, and ignition circuit variations. Compare simple contact point systems with electronic ECM-controlled ignition systems. Distinguish between distributorless and direct ignition systems.

5 Objectives Explain the need for accurate ignition timing control.
Describe the three basic methods used to control ignition system spark timing. Correctly answer ASE certification test questions that require knowledge of ignition system theory and design.

6 Ignition System Fundamentals
Amplifies battery voltage or charging system voltage to over 40,000 volts, and delivers it to spark plugs Gasoline engines use ignition system to initiate combustion on the power stroke Diesels are compression ignition engines Do not need ignition system to start combustion

7 Ignition System Fundamentals (Cont.)
Basic ignition system parts Crankshaft position sensor Primary wires Ignition control module Ignition coil Spark plugs Secondary wires Ignition switch

8 Ignition System Operation
Ignition system supply voltage feeds to ignition system by battery or alternator Battery provides electricity for starting engine After engine is running, alternator supplies slightly higher voltage to battery and ignition system

9 Primary and Secondary Circuits
Primary circuit All components and wires operating on low 12-volt dc from battery, alternator, or current from HV power control module Secondary circuit All parts carrying high-voltage current Wires and parts between coil output windings and spark plug ground

10 Primary and Secondary Circuits (Cont.)
Secondary operating voltage of ignition system ranges from 4,000–100,000 volts, depending on system design

11 Ignition System Supply Voltage
Fed to ignition system by battery, alternator, or HV power control module 12-volt or HV battery provides electricity for starting engine After engine is running, alternator or HV PCM supply slightly higher voltage

12 Bypass Circuit Bypass circuit
Used in older ignition systems to supply direct battery voltage to ignition system during starting

13 Resistance Circuit Special resistance wire Ballast resistor
Wire having internal resistance Ballast resistor Heat sensitive resistor that regulates voltage to ignition coil Used in resistance circuit Ensures relatively steady voltage of about 9.5–10.5 volts applied to ignition system

14 Secondary Wires Coil wire Spark plug wires
Carries high-voltage current from ignition coil to distributor cap Spark plug wires Carries coil voltage from distributor cap to spark plugs Conductor is stranded metal wire No longer used because they cause radio interference Insulated boots fit over both ends to protect metal connectors

15 Secondary Wires (Cont.)
Resistance wires or radio suppression wires Used for most secondary wire applications because they contain internal resistance, which helps prevent radio interference (Champion Spark Plugs)

16 Spark Plugs Use ignition coil high voltage to ignite fuel mixture
Basic parts Center terminal (center electrode) Grounded side electrode Ceramic insulator Steel shell

17 Spark Plugs (Cont.) Spark plug reach Resistor spark plug
Distance between end of plug threads and seat or sealing surface on plug shell Resistor spark plug Internal resistance (around 10,000 ohms) to reduce static in radios and television sets Non-resistor spark plug Solid metal rod forming center electrode

18 Spark Plugs (Cont.) Spark plug gap Spark plug heat range
Distance between center and side electrodes Normal gap specifications range from 0.030"–0.080" (0.76 mm–2.0 mm) Spark plug heat range Rating of spark plug tip’s operating temperature

19 Spark Plugs (Cont.) Hot spark plug Cold spark plug
Long insulator tip and tends to burn off deposits Cold spark plug Shorter insulator tip Operates at cooler temperature Used in engines that operate at high speeds

20 Spark Plugs (Cont.) (Chrysler)

21 Ignition Coils Ignition coil Ignition coil open-circuit voltage
Pulse-type transformer that produces short bursts of high voltage to start combustion Ignition coil open-circuit voltage Maximum voltage potential Ranges from 40,000–100,000 volts in late-model designs

22 Ignition Coils (Cont.) Two primary terminals Iron core
High-voltage terminal Primary windings Several hundred turns of heavy wire Secondary windings Several thousand turns of very fine wire (Chrysler)

23 Ignition Coil Operation
Current flows through primary windings creating a strong magnetic field Iron core concentrates and strengthens this field When current is interrupted, magnetic field collapses Secondary windings have more turns than primary windings Up to 60,000 volts induced

24 Ignition Coil Operation (Cont.)
High voltage shoots out of high-voltage terminal Traveling through secondary circuit to spark plug (Saab)

25 Ignition Coil Designs Coil pack Waste-spark ignition coil
Several ignition coils combined into one assembly Used in distributorless ignition systems Waste-spark ignition coil Wired so it fires two spark plugs at the same time Direct ignition coil Bolts directly over top of spark plug on top of engine Fires only on power strokes for maximum efficiency

26 Distributorless Ignition System
Also called computer-coil ignition Crankshaft-triggered ignition system Multiple ignition coils Coil control unit Engine sensors Computer (engine control module) Operate sparks plugs Distributor not needed in this type of system

27 Distributorless Ignition System (Cont.)
Electronic coil module Consists of two or more ignition coils and coil control unit Each coil in module serves two cylinders

28 Distributorless Ignition System (Cont.)

29 Distributorless Ignition System Operation

30 Direct Ignition System
One coil assembly mounted directly above each spark plug Eliminates need for spark plug wires Allows use of smaller ignition coils Other components in direct ignition system are the same as those in distributorless system

31 Direct Ignition System (Cont.)
Ionization knock sensing system Detects abnormal combustion and knocking Dual spark plug ignition system Two spark plugs used in each cylinder Multiple discharge ignition system Fires spark plugs more than once during each power stroke

32 Distributor Ignition Systems
Used in older ignition systems Actuates on/off cycles of current flow through ignition coil primary windings It causes spark to occur at each plug earlier in compression stroke as engine speed increases and vice versa It changes spark timing with changes in engine load

33 Distributor Ignition Systems (Cont.)
Sometimes, bottom of distributor shaft powers engine oil pump Some distributors house ignition coil and electronic switching circuit in one assembly Unitized distributors

34 Distributor Ignition Systems (Cont.)
Distributor types Contact point distributor Pickup coil distributor Hall-effect distributor Optical distributor Distributor drive Refers to method used to rotate distributor shaft to match engine rpm

35 Contact Point Ignition Systems
Contact point distributor major parts Distributor cam Contact points (breaker points) Condenser (capacitor) Point dwell or cam angle Amount of time contact points remain closed between each opening Point gap Distance between fully open contact points

36 Contact Point Ignition Systems (Cont.)
(Deere & Co.)

37 Point Dwell Amount of time contact points remain closed between each opening Without enough point dwell, a weak spark would be produced (Echlin)

38 Electronic Ignition System
Also called solid-state system or transistor ignition system Uses ignition control module and either distributor pickup coil, Hall-effect device, or optical pickup to operate ignition coil More dependable than contact point system No mechanical breakers to wear or burn

39 Pickup Coil Also called sensor assembly or sensor coil
Produces tiny voltage pulses that are sent to ignition control module Trigger wheel Also called reluctor or pole piece Fastened to upper end of distributor shaft Replaces distributor cam Has one tooth for each engine cylinder

40 Pickup Coil (Cont.)

41 Hall-Effect Pickup Solid-state chip or module
Produces electrical signal when triggered by slotted wheel Constant amount of current sent through device Permanent magnet located next to Hall-effect chip (Ford)

42 Optical Pickup Slotted rotor plate rotates between LEDs and photo diodes When slot passes, light from LED strikes photo diode Electrical signal is generated (Nissan)

43 Ignition Control Modules
“Electronic switch” Turns ignition coil primary current on and off Module does same thing as opening and closing contact points

44 Crankshaft-Triggered Ignition
Can maintain more precise ignition timing than system with distributor-mounted pickup Crankshaft trigger wheel Also called pulse ring or reluctor ring Provides engine speed and crankshaft position data for sensors and computer Performs same function as trigger wheel in electronic ignition’s distributor

45 Crankshaft-Triggered Ignition (Cont.)
(Robert Bosch)

46 Engine Firing Order Sequence in which spark plugs fire to cause combustion in each cylinder Firing order information used when Installing plug wires Checking ignition timing (Mitchell Manuals and Echlin)

47 Ignition Timing Ignition timing or called spark timing Timing advance
How early or late spark plugs fire in relation to engine pistons’ position Timing advance Occurs when spark plugs fire sooner during engine’s compression strokes Timing retard Occurs when spark plugs fire later during compression strokes

48 Ignition Timing (Cont.)
Three basic methods to control ignition system spark timing Electronic advance Distributor centrifugal advance Distributor vacuum advance

49 Electronic (Computer) Spark Advance
Engine sensors, ignition control module, and computer adjusts ignition timing Engine sensors Check various operating conditions Send data to computer Computer analyzes data Changes timing for maximum efficiency

50 Electronic Spark Advance (Cont.)
Sensors that influence ignition timing Crankshaft position sensor Camshaft position sensor Manifold absolute pressure sensor Intake air temperature sensor Engine coolant temperature sensor Knock sensor Throttle position sensor

51 Distributor Centrifugal and Vacuum Advance
Distributor centrifugal advance Ignition coil and spark plugs fire sooner as engine speed increases Distributor vacuum advance Additional spark advance at part throttle positions when engine load is low (Robert Bosch)

52 Base Ignition Timing All late-model cars use computers to control ignition timing advance To check timing, may have to trigger computer to go to base timing Base timing is ignition timing without computer controlled advance


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