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Chapter 9 Ignition Systems page 147.

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1 Chapter 9 Ignition Systems page 147

2 Basic Ignition System Operation
charge builds up in coil (12 volts in) creates a magnetic field (windings of wire) voltage is stepped up (secondary windings) switch open (magnetic field collapses) high voltage discharged (to plug)

3 Fundamental Electrical Principles
Electricity is lazy Electricity wants to go to ground electron theory (-) to (+) conventional theory (+) to (-) Conductors Insulators

4 The Electron Theory Electricity moves from – to +

5 Electrical Units of Measurement
Volts---- Push V Current ---Quantity A Resistance ----Resistance to flow 

6 Ohm’s Law E = I x R E / I = R E / R = I E I R

7 Magnetism Alike charges repel (-) (-)
Dissimilar charges attract (-) (+)

8 Magnets & Electricity Magnets can be used to for electricity
Electricity can be used to form magnets Electricity when applied to magnets make stronger magnets

9 Ignition Coils Coils of wire wrapped around an iron core
Step up transformer

10 Spark Plugs Spark plugs contain an air gap for electricity to create a spark and make a seal

11 Heat Ranges The difference between a "hot" and a "cold" spark plug is in the shape of the ceramic tip. The manufacturers will select the right-temperature plug for each engine. Some engines with high-performance naturally generate more heat, so they need colder plugs. If the spark plug gets too hot, it could ignite the fuel before the spark fires It is important to stick with the right type of plug Engine that burn oil may need hot plugs

12 Measuring Spark Plug Temperature

13 Types of Electrodes Center electrode Side electrode

14 Switching Devices Breaker points Electronic

15 Breaker Points Ran by cam shaft

16 Electronic Switching Devices
NO breaker points to burn or wear out

17 The MBI Magneto System Mechanical Breaker Point Ignition
produce power without an outside power source Condenser-prevents arching

18 The MBI Magneto Cycle Magnets pass legs

19 Coil 150 turns of large wire 20,000 turns of fine wire Iron core

20 The Stop Switch Plug only fires when points open Switch grounds points
Fasten metal to head bold

21 Ignition Advance Systems
Cause spark earlier BTDC As engine warms up Speeds up Centrifugal Vacuum Mechanical

22 Dwell & Cam Angles Time points stay closed Lobes size = dwell time

23 Electronic Ignition Solid state No maintenance No points-burning
Spark plug life Easy starting Higher output Starts flooded engine Higher spark output

24 Electronic Ignition Hermetically sealed Uniform performance
Good under adversity Improved idling Smoother power under load

25 Operation of Capacitive Discharge Ignition ( CDI)
Solid State Newest NO Breaker points Magnets only moving parts

26 Operation of Transistor Controlled Ignition (TCI) Systems

27 Magneto Ignition Systems Compared

28 Battery Ignition Systems
Low voltage primary circuit High voltage secondary circuit ignition switch builds field field collapses spark to plug

29 High Voltage Secondary Circuits
Uses a step up transformer Several winding of wire / iron core

30 Auto-Transformer Type Ignition Coils

31 The Lead Acid Battery

32 Vehicle batteries

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