MSD 6421 6AL-2 Ignition Control Installation - Manual

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Parts Included:
1 - MSD Ignition 1 - Screwdriver 4 - Vibration Mounts
1 - Harness, PN 8860 1 - Parts Bag, ASY 28928
WARNING: During installation, disconnect the battery cables. When disconnecting the battery always
remove the Negative cable first and install it last.
Note: Solid Core spark plug wires cannot be used with an MSD Ignition.
Note: Do not use digital or dial back timing lights.
LED INDICATOR
There is an LED that monitors the status of the Ignition. The LED monitors the trigger signals and will
flash to warn if the supply voltage drops below 9 volts while under 3,000 rpm.
OPERATION AND FEATURES
DIGITAL OPERATION
The MSD 6AL-2 uses a high speed RISC microcontroller to control the ignition's output while constantly
analyzing the various inputs such as supply voltage, trigger signals and rpm. The high speed con-
troller can make extremely quick compensations to the output voltage, multiple spark series, timing
and rpm limits while maintaining accurate timing signals to within 1° and 1% of the rpm limits. The
circuits and controller of the 6AL-2 have been thoroughly filtered to create protection against Electro
Magnetic Interference (EMI).
CAPACITIVE DISCHARGE
The MSD 6AL-2 features a capacitive discharge ignition design. The majority of stock ignition
systems are inductive ignitions. In an inductive ignition, the coil must store and step up the voltage
to maximum strength in between each firing. At higher rpm, since there is less time to charge the coil
to full capacity, the voltage falls short of reaching maximum energy which results in a loss of power
or top end miss.
The MSD Ignition features a capacitor which is quickly charged with 520 - 535 volts and stores it until
the ignition is triggered. With the CD design, the voltage sent to the coil is always at full power even
at high rpm.
MULTIPLE SPARKS
The MSD produces full power multiple sparks for each firing of a plug. The number of multiple sparks
that occur decreases as rpm increases, however the spark series always lasts for 20° of crankshaft
rotation. Above 3,000 rpm there is simply not enough “time” to fire the spark plug more than once,
so there is only one powerful spark.
PROTECTION
The MSD 6AL-2 has a built in reverse polarity protection circuit. This will protect the ignition in the
event of wrong connections. It will also shut off for protection from a surge in power. The ignition will
still operate once the surge or polarity is corrected.
MSD 6AL-2 Ignition Control
PN 6421
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