IGNITION TIMING. Man, did that feel like 40,000 Volts!!!

IGNITION TIMINGIGNITION TIMING

Man, did that feel Man, did that feel like 40,000 Volts!!!like 40,000 Volts!!!

IGNITION TIMING FACTORSIGNITION TIMING FACTORS

Ignition timing is how early or late Ignition timing is how early or late spark plugs fire in relation to spark plugs fire in relation to position of engine pistonsposition of engine pistons

Ignition timing must vary with engine Ignition timing must vary with engine speed, load and temperaturespeed, load and temperature

Must be advanced at times and Must be advanced at times and retarded at other timesretarded at other times

METHODS OF IGNITION METHODS OF IGNITION TIMINGTIMING

DISTRIBUTOR CENTRIFUGAL DISTRIBUTOR CENTRIFUGAL ADVANCEADVANCE

DISTRIBUTOR VACUUM ADVANCEDISTRIBUTOR VACUUM ADVANCE ELECTRONIC (COMPUTER) ELECTRONIC (COMPUTER)

ADVANCEADVANCE

IGNITION TIMING IGNITION TIMING COMPENSATES FOR BURN COMPENSATES FOR BURN

TIMETIME

CENTRIFUGAL ADVANCECENTRIFUGAL ADVANCE

VARIES IN DIRECT VARIES IN DIRECT RELATION TO ENGINE RELATION TO ENGINE RPMRPM

CENTRIFUGAL FORCE CENTRIFUGAL FORCE THROWS WEIGHTS OUTTHROWS WEIGHTS OUT

ALLOWS SPARK TO ALLOWS SPARK TO HAPPEN SOONER TO HAPPEN SOONER TO ALLOW ENOUGH TIME ALLOW ENOUGH TIME FOR COMBUSTION TO FOR COMBUSTION TO TAKE PLACE ON POWER TAKE PLACE ON POWER STROKE.STROKE.

FIG 5-34

VACUUM ADVANCEVACUUM ADVANCE

Provide advance at Provide advance at lower engine lower engine speeds and part speeds and part throttle operationthrottle operation

Matches timing to Matches timing to engine loadengine load

Controlled by Controlled by venturi vacuum or venturi vacuum or manifold vacuummanifold vacuum

FIG 5-35

ELECTRONIC SPARK ELECTRONIC SPARK TIMINGTIMING

Distributor does not have a Distributor does not have a centrifugal or vacuum advance centrifugal or vacuum advance mechanismmechanism

Uses engine sensors as inputs to Uses engine sensors as inputs to computercomputer

You must disable spark advance You must disable spark advance when setting base timing on when setting base timing on computer controlled carscomputer controlled cars

DISTRIBUTORLESS DISTRIBUTORLESS IGNITION SYSTEMIGNITION SYSTEM

ENGINE FIRING ENGINE FIRING ORDERORDER

REFERS TO REFERS TO SEQUENCE SPARK SEQUENCE SPARK PLUGS FIREPLUGS FIRE

CAST INTO INTAKE CAST INTO INTAKE MANIFOLDMANIFOLD

EACH ENGINE WILL EACH ENGINE WILL HAVE DIFFERENT HAVE DIFFERENT FIRING ORDERFIRING ORDER

MUST USE DURING MUST USE DURING TUNE-UPTUNE-UP

FIG 5-3