Ignition system
- 1. Requirements of Ignition System 1. Spark plug electrodes must be synchronously timed w.r.t cylinder-piston position at all speeds & loads 2. Sufficiently strong spark to burn lean-mixtures 2.1 Requires higher voltage 2.2 Increased electrical insulation 3. Sufficient spark duration 4. Spark should be produced even when electrodes are shunted 4.1 Carbon, oil, lead, liquid fuel, water condensation deposits 5. Should consume minimum power 6. Should have service life at least equal to that of engine 7. Should not cause radio interference 8. Should be easy to maintain 9. Should be light & compact, cheap & convenient to handle 10. Should be adaptable to mass production
- 2. Types of Ignition System 1 Contact-Point Ignition System 2. Electronic Ignition System 1.1 Battery Ignition System 1.2 Magneto Ignition System Uses mechanical contact breaker switch to make & break the contact Uses battery for power supply to produce sparks Generates its own ignition current 1.2.1 Rotating Magnet Type Magneto Ignition System 1.2.2 Rotating Armature Type Magneto Ignition System 1.2.3 Polar Inductor Type Magneto Ignition System 2.1 Distributor Type with mechanical centrifugal & vacuum advance 2.2 Distributor Type with electronic spark advance 2.3 Distributorless Type with multiple ignition coils 2.4 Distributorless Type with direct capacitor-discharge (CD) ignition for each spark plug
- 3. Components of Battery Ignition System 1 Battery 2 Ignition Switch 3 Ignition Coil 4 Distributor 6 High Tension Ignition Cables 5 Spark Plugs 4.1 Capacitor 4.2 Contact Breaker 4.3 Centrifugal Advance Mechanism 4.4 Vacuum Advance Mechanism 3.1 Primary Coil 3.2 Secondary Coil
- 4. Breakdown Voltage of Air-Gap 1 It depends on: 1.1 Air gap: Larger air-gap requires higher voltage 1.3 Polarity of plug electrodes 1.2 Condition of plug electrodes: 1.4 Condition of plug insulation 1.5 Moisture on distributor-cap & spark-plugs 1.6 Pressure, temperature, type of Mixture in combustion chamber 1.2.1 Used spark-plugs require higher voltage 1.2.2 Round center-electrode requires higher voltage 1.6.2 Lean mixtures requires higher voltage for stronger spark 1.6.1 Higher combustion pressures requires higher voltage
- 5. Disadvantages of Contact Point Ignition 1 Inertia of mechanical components like contact-breaker 2 Insufficient dwell period to build adequate coil magnetic field strength at high engine speeds 3 Wear of contact-breaker