Unit III: Ignition System
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Questions and Answers

What is the primary function of the secondary ignition circuit in a battery ignition system?

  • To regulate the fuel supply to the engine
  • To generate the high voltage necessary for spark plug operation (correct)
  • To sense the engine speed and crankshaft position
  • To provide a low voltage supply to the primary windings of the coil

    • What is the main difference between spark ignition and compression ignition systems?

  • The type of fuel used in the engine
  • The method of ignition initiation (correct)
  • The engine speed and load conditions
  • The compression ratio of the engine

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

  • To interrupt the primary circuit to create a spark (correct)
  • To regulate the fuel supply to the engine
  • To sense the engine speed and crankshaft position
  • To generate the high voltage necessary for spark plug operation

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

    <p>5,000 to 20,000 volts</p> Signup and view all the answers

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

    <p>To sense the engine speed and crankshaft position</p> Signup and view all the answers

    What is the primary 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 effect of increasing the speed of relative movement between the magnetic field and conductors in the ignition coil?

    <p>An increase in the voltage induced into the coil windings</p> Signup and view all the answers

    What is the purpose 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 typical number of turns in the secondary winding of the ignition coil?

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

    Why is the primary winding placed over the secondary winding in the ignition coil?

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

    What is the typical range of capacitance for automotive capacitors?

    <p>0.20 to 0.30 microfarads</p> Signup and view all the answers

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

    <p>To open and close the primary circuit 4 times per revolution</p> Signup and view all the answers

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

    <p>28000-30000 volts</p> Signup and view all the answers

    What is the primary effect of advancing timing on an engine's performance?

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

    What is the primary component used to generate electric current in a magneto ignition system?

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

    Which type of ignition advance mechanism is primarily used in older mechanical distributor-based ignition systems?

    <p>Centrifugal advance mechanism</p> Signup and view all the answers

    Under what condition does the vacuum advance mechanism typically retard the timing advance?

    <p>During heavy load or full throttle conditions</p> Signup and view all the answers

    What is the primary purpose of adjusting ignition timing in an internal combustion engine?

    <p>To optimize engine performance, fuel efficiency, and emissions</p> Signup and view all the answers

    What is the primary purpose of the centrifugal weights in a centrifugal advance mechanism?

    <p>To move outward as engine speed increases</p> Signup and view all the answers

    What is the primary advantage of using a combination of centrifugal and vacuum advance mechanisms?

    <p>Improved engine efficiency and smoother operation</p> Signup and view all the answers

    What is the primary function of an ignition system in an internal combustion engine?

    <p>To generate a high-voltage spark at the right moment to ignite the air-fuel mixture</p> Signup and view all the answers

    Which component of the ignition system is responsible for distributing high voltage to the correct spark plug at the precise time?

    <p>Distributor (or Ignition Module)</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 purpose of the ignition coil in the ignition system?

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

    What controls the timing of the spark in a modern ignition system?

    <p>Engine's Electronic Control Unit (ECU)</p> Signup and view all the answers

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

    <p>To create a magnetic field in the coil around the soft iron core</p> Signup and view all the answers

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

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

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

    <p>To produce a very high voltage in the secondary winding when the magnetic field is collapsed</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 term for the loss of electrical charge from a capacitor?

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

    What is the primary advantage of electronic ignition systems over mechanical advance mechanisms in modern engines?

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

    What is the purpose of the starter solenoid in the starting system of an automobile?

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

    Which component of the starting system is responsible for providing electrical energy to power the system?

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

    What is the function of the flywheel or flexplate in the starting system of an automobile?

    <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 in the starting system of an automobile?

    <p>To operate the starter relay and activate the starter solenoid</p> Signup and view all the answers

    What is the primary function of the neutral safety switch in automatic transmission vehicles?

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

    What is the purpose of the overrunning clutch mechanism in the Bendix drive?

    <p>To allow the pinion gear to spin freely in one direction and lock it in the opposite direction</p> Signup and view all the answers

    What happens when the pinion gear engages with the flywheel ring gear in the Bendix drive?

    <p>The rotation of the starter motor is transferred to the engine's crankshaft via the flywheel</p> Signup and view all the answers

    What is the purpose of the drive housing in the Bendix drive?

    <p>To prevent contamination and ensure proper operation of the Bendix drive</p> Signup and view all the answers

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

    <p>It disengages from the flywheel ring gear and spins freely</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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    Description

    Learn about the crucial components of an ignition system in internal combustion engines, including its primary function and key parts.

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