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Ignition system
1. •Provides a method of turning a spark ignition engine on & off.
•Operates on various supply voltages (Battery & Alternator)
•Produces high voltage arcs at the spark plug electrode.
•Distributes spark to each plug in correct sequence.
•Times the spark so that it occurs as the piston nears the TDC on the
compression stroke.
•Varies the ignition timing as engine speed, load and other conditions
change.
2. BATTERY provides power for system.
IGNITION SWITCH allows driver to turn ignition on and off.
IGNITION COIL changes battery voltage to 30,000V during
normal operation and has a potential to produce up to 60,000V.
SWITCHING DEVICE mechanical or electronic switch that operates
Ignition coil(Pick-up coil, Crank sensor, Cam sensor).
SPARK PLUG uses high voltage from ignition coil to produce an arc
in the combustion chamber.
IGNITION SYSTEM WIRES connect components.
3. PRIMARY CIRCUIT
•Includes all the components
working on low voltage
(Battery, Alternator).
SECONDARY CIRCUIT
•Consists of wires and points
between coil out-put and the
spark plug ground.
4.
5. Primary Windings are made up of several
hundred turns of heavy wire wrapped around
or near the secondary windings.
Secondary Windings consist of several thousand
turns of very fine wire, located inside or near
the secondary windings.
6. •Actuates the on/off cycle of current flow through the ignition coil
primary windings.
•It distributes the coils high voltage to the plugs wires.
7. •It causes the spark to occur at each plug earlier in the compression
stroke as engine speed increases, and vice versa.
•Changes spark timing.
•Some distributor shafts operate the oil pump.
9. Points are wired in Primary Circuit – When the points are closed,
a magnetic field builds in the coil. When the points open, the field
collapses and voltage is sent to one of the spark plug.
13. •Transfers voltage from the distributor cap
center terminal(coil) to distributor cap
outer terminals(spark plugs).
•Provides spark in the correct Firing
Order.
•Sometimes the firing order can be found
on the intake manifold.
14. How early or late the spark plug fires in relation to the position of the
engine piston.
Ignition timing must change with the changes in engine speed, load,
and temperature.
15. Timing Advance occurs when the plug fires sooner on compression
stroke (High engine speed)
Timing Retard occurs when plug fires later on compression stroke
(Lower engine speed)
BASE TIMING Timing without vacuum or computer control.
16. Distributor Centrifugal Advance
•Controlled by engine speed.
•Consists of two weights and two springs.
•At high speeds the weights fly out(held by the springs), rotating the
cam, hence advancing the timing.
17. Vacuum Advance
•Controlled by engine intake manifold vacuum and engine load.
•The vacuum diaphragm rotates the pickup coil against the direction
of distributor shaft rotation.
18. Electronic Advance Sensors input influences the ignition timing.
•Crank shaft Position Sensor (RPM)
•Cam Position Sensor (tells which
cylinder is on compression stroke)
•Manifold Absolute Pressure (MAP)
(engine vacuum and load)
19. Electronic Advance Sensors input influences the ignition timing.
•Intake Air Temperature Sensor
•Knock Sensor (Retards timing when pinging
or knocking is sensed)
•Throttle Position Sensor(TPS)
•Engine coolant Temperature
21. •Less moving parts.
•No Distributor.
•Uses multiple ignition coils.
•Camshaft position sensor is installed in place of ignition distributor.
•ECM fires two coils at the same time.
