Unit III: Ignition System
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Questions and Answers

What is the primary function of an ignition system?

  • To supply fuel to the engine's cylinders
  • To generate a high-voltage spark at the right moment to ignite the air-fuel mixture (correct)
  • To generate a low-voltage spark
  • To control the engine's speed

    • What is the primary function of an ignition system?

  • To distribute fuel to the cylinders
  • To produce a high voltage necessary to produce a spark at the plug gap (correct)
  • To generate power for the engine
  • To cool the engine

    • What is the role of the battery in an ignition system?

  • To distribute high voltage to the spark plugs
  • To control the ignition system's operation
  • To provide electrical power to the ignition system (correct)
  • To generate a high-voltage spark

    • What is the typical voltage range required to produce a spark at the plug gap?

    <p>5000-20000 volts</p> Signup and view all the answers

    What is the function of the ignition coil?

    <p>To convert low voltage into high voltage</p> Signup and view all the answers

    What is the term used to describe the ignition process in diesel engines?

    <p>Compression Ignition</p> Signup and view all the answers

    What is the role of the distributor in an ignition system?

    <p>To distribute high voltage to the correct spark plug at the precise time</p> Signup and view all the answers

    What is the function of the spark plugs?

    <p>To create a spark to ignite the air-fuel mixture</p> Signup and view all the answers

    What is the purpose of the contact breaker in a battery ignition system?

    <p>To open and close the primary circuit</p> Signup and view all the answers

    What is the function of the timing sensor in an electronic ignition system?

    <p>To sense engine speed and adjust ignition timing</p> Signup and view all the answers

    What is the typical voltage supplied by the battery to the ignition coil?

    <p>12 volts</p> Signup and view all the answers

    What is the name of the system that uses a carburetor or fuel injection system to initiate combustion?

    <p>Spark Ignition</p> Signup and view all the answers

    What controls the timing of the spark in an ignition system?

    <p>The engine's electronic control unit (ECU)</p> Signup and view all the answers

    What is the purpose of the capacitor in a battery ignition system?

    <p>To filter out electrical noise</p> Signup and view all the answers

    What type of ignition system uses a mechanical distributor to control spark timing?

    <p>Conventional (Mechanical) Ignition System</p> Signup and view all the answers

    What is the name of the system that uses a magneto to generate power for the ignition system?

    <p>Magneto Ignition System</p> Signup and view all the answers

    What is the purpose of the distributor cap and rotor in a battery ignition system?

    <p>To distribute the spark to all the cylinders</p> Signup and view all the answers

    What is the primary difference between a 2-stroke and 4-stroke cycle engine?

    <p>The number of strokes per cycle</p> Signup and view all the answers

    What is the primary function of the primary winding in an ignition coil?

    <p>To create a magnetic field</p> Signup and view all the answers

    What is the effect of the high ratio of secondary to primary turns in an ignition coil?

    <p>A very high voltage in the secondary circuit</p> Signup and view all the answers

    What is the purpose of the capacitor in the ignition system?

    <p>To store electrical energy</p> Signup and view all the answers

    What determines the capacitance of a capacitor?

    <p>The area of the plates and the distance between them</p> Signup and view all the answers

    What happens when a capacitor is discharged?

    <p>Electrons flow from the negative plate to the positive plate</p> Signup and view all the answers

    What is the unit of capacitance?

    <p>Farad</p> Signup and view all the answers

    What is the effect of increasing the distance between the plates of a capacitor?

    <p>The capacitance decreases</p> Signup and view all the answers

    What is the purpose of the contact breaker points in the ignition coil?

    <p>To break the primary circuit and create a spark</p> Signup and view all the answers

    What is the term for the loss of electrical charge from a capacitor?

    <p>Leakage</p> Signup and view all the answers

    What is the effect of using a thinner dielectric material in a capacitor?

    <p>The capacitance increases</p> Signup and view all the answers

    What is the principle of operation of the ignition coils of inductive ignition systems?

    <p>Electromagnetic induction</p> Signup and view all the answers

    What is the factor that determines the strength of the magnetic field produced in the coil primary winding?

    <p>The strength of the magnetic field itself</p> Signup and view all the answers

    What is the purpose of the laminated soft iron core in the ignition coil?

    <p>To minimize the effects of eddy currents</p> Signup and view all the answers

    What is the function of the outer soft iron cover in the ignition coil?

    <p>To allow circulation of the oil filling for cooling purposes</p> Signup and view all the answers

    What is the purpose of the ceramic insulator at the base of the coil?

    <p>To support the core and winding</p> Signup and view all the answers

    How many turns of very fine insulated copper wire are typically found in the secondary winding?

    <p>Approximately 20,000 turns</p> Signup and view all the answers

    What is the current carried by the primary winding in standard systems?

    <p>Approximately 2 ampere</p> Signup and view all the answers

    Why is the primary winding placed over the secondary winding?

    <p>To give ready access to the cooling oil for the secondary winding</p> Signup and view all the answers

    What is the purpose of the top insulator in the ignition coil?

    <p>To seal the outer case of the coil</p> Signup and view all the answers

    What is the effect of creating a voltage in a conductor by means of relative movement between the conductor and a magnetic field?

    <p>Electromagnetic induction</p> Signup and view all the answers

    What is the main advantage of modern engines with electronic ignition systems?

    <p>More precise control over ignition timing</p> Signup and view all the answers

    What is the primary function of the starter motor?

    <p>To crank the engine by turning the crankshaft</p> Signup and view all the answers

    What is the purpose of the starter solenoid?

    <p>To control the flow of electrical power to the starter motor</p> Signup and view all the answers

    What is the role of the flywheel or flex plate in the starting system?

    <p>To provide a surface for the starter motor's drive gear to engage with</p> Signup and view all the answers

    What is the purpose of the ignition switch?

    <p>To operate the vehicle's electrical systems when the key is turned</p> Signup and view all the answers

    What is the role of the starter relay in some vehicles?

    <p>To act as a remote switch, receiving a low-current signal from the ignition switch</p> Signup and view all the answers

    What is the primary function of the centrifugal and vacuum advance mechanisms?

    <p>To adjust ignition timing based on engine speed and load conditions</p> Signup and view all the answers

    What is the purpose of the bendix drive in the starting system?

    <p>To transmit the torque developed by the starting motor to the engine flywheel</p> Signup and view all the answers

    What is the role of the overrunning clutch in the starting system?

    <p>To allow the starter motor to freewheel once the engine is running</p> Signup and view all the answers

    What is the purpose of the storage battery in the starting system?

    <p>To supply electrical energy to the starter motor and ignition system</p> Signup and view all the answers

    What is the effect of advancing timing on engine performance?

    <p>It improves power and efficiency at higher RPMs</p> Signup and view all the answers

    What is the purpose of retarding timing in an engine?

    <p>To prevent knocking or pre-ignition at lower RPMs</p> Signup and view all the answers

    What is the symptom of incorrect ignition timing in an engine?

    <p>Knocking or pinging sounds from the engine</p> Signup and view all the answers

    What is the purpose of adjusting ignition timing during engine tuning?

    <p>To achieve optimal performance</p> Signup and view all the answers

    What is the typical adjustment made to ignition timing in modern vehicles?

    <p>Adjusting timing within a narrow range set by the manufacturer</p> Signup and view all the answers

    What is the unit of measurement used to express the capacitance of automotive capacitors?

    <p>Microfarad</p> Signup and view all the answers

    What is the primary function of the centrifugal advance mechanism?

    <p>To adjust ignition timing based on engine speed</p> Signup and view all the answers

    What is the purpose of the vacuum advance mechanism?

    <p>To adjust ignition timing based on engine load conditions</p> Signup and view all the answers

    What is the purpose of the auto-transformer in a battery ignition system?

    <p>To step up the voltage</p> Signup and view all the answers

    What is the advantage of using a centrifugal advance mechanism?

    <p>It is more reliable and effective for adjusting ignition timing based on engine speed</p> Signup and view all the answers

    What is the typical number of turns in the primary winding of a battery ignition system?

    <p>200-300 turns</p> Signup and view all the answers

    What happens when the contact breaker opens in a battery ignition system?

    <p>The magnetic field begins to collapse</p> Signup and view all the answers

    What is the advantage of using a vacuum advance mechanism?

    <p>It improves engine efficiency by adjusting timing based on load and vacuum conditions</p> Signup and view all the answers

    What is the purpose of the condenser in a magneto ignition system?

    <p>To send back high voltage high current into the secondary winding</p> Signup and view all the answers

    What type of engines typically use a combination of centrifugal and vacuum advance mechanisms?

    <p>Older engines</p> Signup and view all the answers

    What is the term used to describe the precise moment when the spark plugs fire in the cylinders of an internal combustion engine?

    <p>Ignition timing</p> Signup and view all the answers

    What can be adjusted to optimize engine performance based on factors like engine speed, load, and fuel quality?

    <p>Ignition timing</p> Signup and view all the answers

    What is the difference between advance and retard ignition timing?

    <p>Advance is firing the spark earlier, while retard is firing the spark later</p> Signup and view all the answers

    What is the typical voltage range generated by the secondary winding in a battery ignition system?

    <p>20,000-30,000 volts</p> Signup and view all the answers

    What is the purpose of the distributor rotor in a battery ignition system?

    <p>To distribute the high voltage to the spark plugs</p> Signup and view all the answers

    What is the purpose of the neutral safety switch in an automatic transmission vehicle?

    <p>To prevent the engine from starting unless the transmission is in neutral</p> Signup and view all the answers

    What is the primary function of the Bendix drive?

    <p>To engage and disengage the starter motor from the engine's flywheel ring gear</p> Signup and view all the answers

    What is the component of the Bendix drive that allows the pinion gear to spin freely in one direction?

    <p>Overrunning clutch mechanism</p> Signup and view all the answers

    What happens to the pinion gear once the engine starts running?

    <p>It disengages from the flywheel ring gear</p> Signup and view all the answers

    What is the purpose of the starter motor in an engine?

    <p>To crank the engine</p> Signup and view all the answers

    What prevents the starter motor from being driven by the engine once it starts running?

    <p>The overrunning clutch mechanism</p> Signup and view all the answers

    What is the component of the Bendix drive that houses the pinion gear and overrunning clutch mechanism?

    <p>Drive housing</p> Signup and view all the answers

    What is the purpose of the ignition key in an engine start sequence?

    <p>To release the starter motor from the engine's flywheel ring gear</p> Signup and view all the answers

    What is the typical direction of rotation of the pinion gear in a Bendix drive?

    <p>In the same direction as the starter motor's rotation</p> Signup and view all the answers

    What is the purpose of over cranking protection systems in modern vehicles?

    <p>To prevent excessive cranking of the engine, which could lead to damage or drain the battery excessively</p> Signup and view all the answers

    Study Notes

    Ignition System in Internal Combustion Engines

    • An ignition system is a crucial component in internal combustion engines, responsible for initiating and controlling the combustion process.
    • Its primary function is to generate a high-voltage spark at the right moment to ignite the air-fuel mixture within the engine's cylinders.

    Components of an Ignition System

    • Battery: Provides electrical power to the ignition system.
    • Ignition Switch: Controls the ignition system's operation, allowing the driver to start and stop the engine.
    • Ignition Coil: Converts low voltage from the battery into high voltage, which is necessary to create a spark at the spark plugs.
    • Distributor (or Ignition Module): Distributes high voltage from the ignition coil to the correct cylinder's spark plug at the precise time.
    • Spark Plugs: Devices that create a spark to ignite the air-fuel mixture.

    Types of Ignition Systems

    • Conventional (Mechanical) Ignition Systems: Older systems that use a mechanical distributor to control spark timing.
    • Electronic Ignition Systems: Modern systems that use solid-state electronics and sensors to control ignition timing more precisely, improving efficiency and performance.

    Importance of Ignition System

    • The efficiency and reliability of an ignition system directly impact engine performance, fuel efficiency, and emissions.
    • A well-maintained ignition system ensures smooth engine operation and optimum power output.

    Battery Ignition System

    • Consists of primary ignition circuit (low voltage), secondary ignition circuit (high voltage), ignition switch, contact breaker, capacitor, and spark plugs.
    • The primary ignition circuit supplies low voltage to the ignition coil, which steps up the voltage to generate a high-voltage spark.

    Magneto Ignition System

    • Uses a magneto to generate electric current for producing spark.
    • Main components include frame, permanent magnet, armature, soft iron field, rotor, primary and secondary winding, contact breaker, and condenser.

    Ignition Timing

    • Refers to the precise moment when the spark plugs fire in the cylinders of an internal combustion engine.
    • Timing is crucial because it determines when the fuel-air mixture ignites, which directly affects engine performance, fuel efficiency, and emissions.

    Factors Affecting Ignition Timing

    • Engine speed, load, and fuel quality.
    • Mechanical vs. electronic methods of adjusting ignition timing.
    • Advance and retard timing to optimize engine performance.

    Ignition Advance Mechanism

    • Centrifugal Advance Mechanism:

      • Adjusts ignition timing based on engine speed.
      • Uses centrifugal weights and springs to rotate the distributor shaft and advance the spark timing.

    • Vacuum Advance Mechanism:

      • Adjusts ignition timing based on engine load and vacuum pressure.
      • Uses a vacuum sensor to advance the spark timing when the engine is under load.### Ignition Timing

    • The amount of advance in ignition timing is designed to compensate for the time it takes for combustion to complete at higher engine speeds, optimizing engine performance.

    • Centrifugal advance mechanisms are mechanical and work without additional sensors or electronic controls, making them reliable and effective for adjusting ignition timing based on engine speed variations.

    • Vacuum advance mechanisms are used in conjunction with centrifugal advance to optimize ignition timing based on engine load conditions.

    • During light throttle or low-load conditions, vacuum advance mechanisms advance the timing to improve fuel efficiency and reduce emissions.

    • Under heavy load or full throttle, vacuum advance mechanisms retard the timing to prevent knocking or pre-ignition.

    Starting System

    • The starting system is responsible for initiating the engine's operation from a stationary position.
    • Components of the starting system include:
      • Battery: provides electrical energy to power the starting system
      • Starter Motor: an electric motor specifically designed for high torque output
      • Starter Solenoid: a relay switch that controls the high current needed to operate the starter motor
      • Ignition Switch: controls the flow of electrical power to the starter solenoid and other electrical systems
      • Starter Relay: controls the flow of current to the starter solenoid (in some vehicles)
      • Flywheel or Flex plate: toothed wheel attached to the engine's crankshaft
    • Operation of the starting system involves:
      • Initiation: electrical power flows from the battery to the starter motor
      • Starter solenoid activation: the starter relay or ignition switch sends a signal to the starter solenoid
      • Starter motor engagement: the starter motor spins and its drive gear extends to engage with the flywheel or flex plate teeth
      • Cranking the engine: the starter motor cranks the engine by turning the flywheel or flex plate
      • Engine start: the engine fires and begins to run under its own power

    Bendix Drive

    • The Bendix drive is a type of starter drive mechanism commonly used in automobile starter motors.
    • Its primary function is to engage the starter motor with the engine's flywheel ring gear to start the engine.
    • The Bendix drive consists of a pinion gear mounted on an overrunning clutch mechanism.
    • The pinion gear is typically a helical gear mounted on a shaft connected to the armature shaft of the starter motor.
    • The overrunning clutch allows the pinion gear to spin freely in one direction and locks it in the opposite direction, engaging with the flywheel.
    • The working process of the Bendix drive involves:
      • Starting process initiation: electrical current flows to the starter solenoid, which activates the starter motor
      • Pinion gear movement: the Bendix drive shaft rotates, moving the pinion gear towards the flywheel due to centrifugal force or a mechanical mechanism
      • Engagement with flywheel: the pinion gear engages with the flywheel ring gear, meshing with the teeth and transferring rotational motion from the starter motor to the engine's crankshaft
      • Engine starting: the engagement allows the starter motor to crank the engine
      • Automatic disengagement: once the engine starts running, the overrunning clutch mechanism allows the pinion gear to spin freely, disengaging it from the flywheel ring gear.

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    Learn about the components and functions of an ignition system in internal combustion engines, including its primary function of generating a high-voltage spark.

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