here continues with the basic types of transistor ignition
systems (breaker-point and magnetic-pulse), the
capacitor discharge ignition system, the Chrysler
electronic ignition system, the Delco-Remy unitized
ignition system, and the Ford computerized ignition
system.
TRANSISTOR IGNITION SYSTEM
(BREAKER-POINT TYPE)
The breaker-point type of transistor ignition system
was developed to replace the standard or conventional
ignition system. To obtain the maximum power and
speed that this engine can produce, you must install an
ignition system that outperforms the conventional one.
Electronic type of ignition systems provide a hotter,
more uniform spark at a more precise interval. This
promotes more efficient burning of the air/fuel mixture
in the combustion chamber, producing less exhaust
emissions, and resulting in better engine performance
and increased mileage. The increased reliability of
electronic ignition allows less frequent maintenance by
increasing parts life. At high speeds, the breaker points
of a conventional ignition system cannot handle the
increased current flowing across them without pitting
too much. Also, the dwell angle of the breaker points is
too small for complete saturation of the ignition coil.
The transistorized ignition system takes care of both
drawbacks.
By comparing figures 4-28 and 4-29, you can see
how the transistor ignition system differs from the
conventional. When the breaker points are connected to
the transistor, as shown in figure 4-29, it nearly
eliminates arcing across them since the current flow is
small (about one-half ampere). However, the current
flow in the primary windings of the coil is about 6
amperes. This amount is enough to saturate the coil
completely at high engine speeds, and results in a higher
output to the secondary circuit. Therefore, the transistor
ignition system is superior to the conventional system at
high engine speeds because there is less arcing across
Figure 4-28.-Conventional ignition system.
Figure 4-29.-Transistor ignition system (breaker-point type).
the breaker points and higher and steadier voltage in the
secondary circuit.
TRANSISTOR IGNITION SYSTEM
(MAGNETIC-PULSE TYPE)
The drawbacks of a conventional ignition system
operating at high engine speeds can also be overcome
with the magnetic-pulse type of transistor ignition
system (fig. 4-30). Notice that a magnetic pulse
distributor, which resembles a conventional distributor,
is used instead of a breaker-point type of distributor. An
iron timer core in this distributor replaces the standard
breaker cam. The timer core has equally spaced
projections (one for each cylinder of the engine) and
rotates inside a magnetic pickup assembly. This pickup
assembly replaces the breaker plate assembly of the
conventional distributor. Since there are no breaker
points and there is no condenser, there can be no arcing
across them. Capacitors in this system are for noise
suppression. This overcomes one of the drawbacks
already mentioned. The other drawback is overcome by
controlling the amount of current that flows through the
primary windings of the ignition coil and to ground.
Transistors in the ignition pulse amplifier do the
controlling. Another feature of this transistor ignition
system is its coil, which has fewer and heavier primary
windings and a higher turns ratio of primary to
secondary windings than the conventional coil.
Controlling the current flow and using a special coil
Figure 4-30.-Magnetic-pulse type transistor ignition system.
4-16
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