Technical information

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN, EL PASO, TEXAS 79936 • [phone] • FAX [phone]
www.msdignition.com email: [e-mail]
9
TACH OUTPUT AND
ADAPTERS
GENERAL INSTALLATION TIPS
Plastic Spacers
MSD no longer supplies the
plastic spacers that were used on
some coil installations. This is due
to the changes in coil housings
and connectors not requiring the
spacers. The spacers were used
to simplify wiring on canister coil
applications. There is no electri-
cal continuity between the coil
post and the outside terminal of the plastic spacer.
BATTERY
The battery is one of the most important parts of
the automotive electrical system. A MINIMUM battery
rating, when used with an alternator, should be no less
than 25 amp/hours. If no alternator is used, allow at
least 15 amp/hour for every 1/2 hour of MSD opera-
tion. If the engine is cranked using the same battery or
other accessories such as fuel pumps and electric fans
are used, the rating should be more.
In all cases, to ensure adequate running time, the
battery should be fully charged at the start of opera-
tion. A fully charged 12 volt battery will read around
12.6 volts on a voltmeter and should not drop below 8
volts when cranking. Each cell of a fully charged bat-
tery will read 1.260 on a hydrometer.
An MSD Ignition Control will operate at full strength
with 11-18 volts.
Here are a few battery tips on charging and jump starts:
•
When charging the battery, DO NOT run the
engine. Some chargers may produce potentially
damaging high voltage spikes that could damage
the ignition control.
•
It is not necessary to disconnect the MSD when
charging the battery, as long as the charger is
making good contact with the battery.
•
Receiving a jump from another battery or car will
not damage the MSD Ignition.
The MSD 6, 7, 8 and 10 Ignition Controls all feature
a Tach Output terminal to provide a trigger signal to
tachometers, an MSD Shift Light, or rpm activated
switches. The Tach Output Terminal produces a 12 volt
square wave signal with a 30% duty cycle. A standard
female faston terminal is supplied for easy installation.
Most factory and aftermarket tachometers will accept
this signal, however there are exceptions (see the chart
on page 10).
Some factory and "budget" tachometers may require
a Tach Adapter to operate correctly. MSD offers a couple
different adapters for various applications. Before pur-
chasing an Adapter, try connecting the tachometer's
trigger wire directly to the MSD's tach output terminal.
If the tach still does not operate (and is properly wired)
you may need a Tach Adapter. There are two main Tach
Adapters available for single channel, MSD Ignitions:
PN 8920: If you are using the magnetic pickup con-
nector (Green and Violet wires) to trigger the MSD,
you need the PN 8920 Adapter.
PN 8910: If your tachometer was originally triggered
from the coil negative terminal (you are using the White
wire of the MSD), you need the PN 8910 Adapter.
The chart on page 10 lists common tachometers.