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INSTALLATION INSTRUCTIONS

THEORY OF OPERATION

CAPACITIVE DISCHARGE

The MSD Digital DIS Series Ignitions feature a capacitive discharge ignition design. The majority of

stock ignitions 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 to 460-480 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 Digital DIS Series Ignition produces full power multiple sparks for each firing of the spark

plug. The number of 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.

REV LIMITER

The MSD DIS-2 and 4 Ignitions are equipped with a built-in adjustable Soft Touch Rev Control. This

rev limit feature can be adjusted in 100 rpm increments using the program switches on the ignition's

end panel. The Soft Touch circuitry provides a smooth and accurate rev limit by dropping the spark

to individual cylinders. The Soft Touch produces a load-free rev limit that is accurate to within 10 rpm

of the selected rpm.

GENERAL INFORMATION

BATTERY

An MSD Digital DIS Series Ignition will operate on any negative ground, 12 volt electrical system

without a distributor. The MSD can be used with a 16 volt battery and can withstand a momentary 24

volts in case of a jump start. The ignition will deliver full voltage with a supply of 12 - 18 volts and will

operate with a supply voltage as low as 8 volts.

If your application does not use an alternator, allow at least 15 amp/hour for every half hour of operation.

If the engine is cranked with the same battery or other accessories such as an electric fuel pump, fan

or water pump are used, the amp/hour rating of the battery must be increased.

COILS

The MSD Digital DIS Ignitions can be used with most stock coils and most aftermarket coils that are

designed to replace the stock coils. If you have any questions concerning coils, contact our MSD

Customer Service Department at (915) 855-7123. Due to the increased energy driving the stock coils,

this ignition should

not be used for street use.

TACHOMETERS/FUEL INJECTION

The MSD Digital Series Ignitions feature a Tach Output Terminal on the side of the unit. This terminal

provides a trigger signal for tachometers, fuel injection, a shift light or other add-on devices that require

a 12 volt square wave rpm signal with a 20° duration.

Some vehicles may require an Ignition Adapter to operate properly with the MSD. For more information

on tachometers and MSD Ignition Adapters, refer to page 13.

NOTE: If you plan on welding on your vehicle, to avoid possible damage to the ignition, always

disconnect both MSD Heavy Power cables from the battery. It is also recommended that the

tach ground wire be disconnected.