Chapter 9Chapter 9

Ignition SystemsIgnition Systems

page 147page 147

Basic Ignition System Operation Basic Ignition System Operation

charge builds up in coil (12 volts in)charge builds up in coil (12 volts in)

creates a magnetic field (windings of wire)creates a magnetic field (windings of wire)

voltage is stepped up (secondary voltage is stepped up (secondary windings)windings)

switch open (magnetic field collapses)switch open (magnetic field collapses)

high voltage discharged (to plug)high voltage discharged (to plug)

Fundamental Electrical Fundamental Electrical PrinciplesPrinciples

Electricity is lazyElectricity is lazy

Electricity wants to go to groundElectricity wants to go to ground

electron theory (-) to (+)electron theory (-) to (+)

conventional theory (+) to (-)conventional theory (+) to (-)

ConductorsConductors

InsulatorsInsulators

The Electron TheoryThe Electron Theory

Electricity moves from – to +Electricity moves from – to +

Electrical Units of MeasurementElectrical Units of Measurement

Volts---- PushVolts---- Push VV

Current ---QuantityCurrent ---Quantity AA

Resistance ----Resistance to flowResistance ----Resistance to flow

Ohm’s LawOhm’s Law

E = I x R E = I x R

E / I = RE / I = R

E / R = IE / R = I E

I R

MagnetismMagnetism

Alike charges repel (-) (-)Alike charges repel (-) (-)

Dissimilar charges attract (-) (+)Dissimilar charges attract (-) (+)

Magnets & ElectricityMagnets & Electricity

Magnets can be used to for electricityMagnets can be used to for electricity

Electricity can be used to form magnetsElectricity can be used to form magnets

Electricity when applied to magnets make Electricity when applied to magnets make stronger magnetsstronger magnets

Ignition CoilsIgnition Coils

Coils of wire wrapped around an iron coreCoils of wire wrapped around an iron core

Step up transformerStep up transformer

Spark PlugsSpark Plugs

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

Heat Heat RangesRanges

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 The manufacturers will select the right-temperature plug for each engine.plug for each engine.

Some engines with high-performance naturally Some engines with high-performance naturally generate more heat, so they need colder plugs.generate more heat, so they need colder plugs.

If the spark plug gets too hot, it could ignite the fuel If the spark plug gets too hot, it could ignite the fuel before the spark firesbefore the spark fires

It is important to stick with the right type of plugIt is important to stick with the right type of plug

Engine that burn oil may need hot plugsEngine that burn oil may need hot plugs

Measuring Spark Plug Measuring Spark Plug TemperatureTemperature

Types of ElectrodesTypes of Electrodes

Center electrodeCenter electrode

Side electrodeSide electrode

Switching DevicesSwitching DevicesBreaker pointsBreaker points

ElectronicElectronic

Breaker PointsBreaker Points

Ran by cam shaftRan by cam shaft

Electronic Switching DevicesElectronic Switching Devices

NO breaker pointsNO breaker points to burn or wear out to burn or wear out

The MBI Magneto SystemThe MBI Magneto System

Mechanical Breaker Point IgnitionMechanical Breaker Point Ignition

produce power without an outside power produce power without an outside power sourcesource

Condenser-prevents archingCondenser-prevents arching

The MBI Magneto CycleThe MBI Magneto Cycle

Magnets pass legsMagnets pass legs

CoilCoil

150 turns of large wire150 turns of large wire

20,000 turns of fine wire20,000 turns of fine wire

Iron coreIron core

The Stop SwitchThe Stop Switch

Plug only fires when points openPlug only fires when points open

Switch grounds pointsSwitch grounds points

Fasten metal to head boldFasten metal to head bold

Ignition Advance SystemsIgnition Advance Systems

Cause spark earlierCause spark earlier

BTDC BTDC

As engine warms upAs engine warms up

Speeds upSpeeds up

CentrifugalCentrifugal

VacuumVacuum

MechanicalMechanical

Dwell & Cam AnglesDwell & Cam Angles

Time points stay closedTime points stay closed

Lobes size = dwell timeLobes size = dwell time

Electronic IgnitionElectronic Ignition

Solid stateSolid stateNo maintenanceNo maintenanceNo points-burningNo points-burningSpark plug lifeSpark plug lifeEasy startingEasy startingHigher outputHigher outputStarts flooded engineStarts flooded engineHigher spark outputHigher spark output

Electronic IgnitionElectronic Ignition

Hermetically sealedHermetically sealed

Uniform performanceUniform performance

Good under adversityGood under adversity

Improved idlingImproved idling

Smoother power under loadSmoother power under load

Operation of Capacitive Operation of Capacitive Discharge Ignition ( CDI)Discharge Ignition ( CDI)

Solid StateSolid State

NewestNewest

NO Breaker pointsNO Breaker points

Magnets only moving partsMagnets only moving parts

Operation of Transistor Operation of Transistor Controlled Ignition (TCI) Controlled Ignition (TCI)

SystemsSystems

Magneto Ignition Systems Magneto Ignition Systems ComparedCompared

Battery Ignition SystemsBattery Ignition Systems

Low voltage primary circuitLow voltage primary circuit

High voltage secondary circuitHigh voltage secondary circuit

ignition switchignition switch

builds fieldbuilds field

field collapsesfield collapses

spark to plugspark to plug

High Voltage Secondary High Voltage Secondary CircuitsCircuits

Uses a step up transformerUses a step up transformer

Several winding of wire / iron coreSeveral winding of wire / iron core

Auto-Transformer Type Ignition Auto-Transformer Type Ignition CoilsCoils

The Lead Acid BatteryThe Lead Acid Battery

Vehicle batteriesVehicle batteries