MSD 7531 Programmable Digital-7 Plus Installation - Manual (Page 15)

INSTALLATION INSTRUCTIONS 15
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• W W W . M S D P E R F O R M A N C E . C O M • ( 9 1 5 ) 8 5 7 - 5 2 0 0 • F A X ( 9 1 5 ) 8 5 7 - 3 3 4 4
CONNECTING THE REV LIMITS
When you connect the Burnout, Launch and Spool Rev Limits, it is important to pay close attention to the
acquisition recording of the ignition. The Light Blue wire is responsible for resetting the Run History, as well
as activating the Burnout Rev Limt. The Dark Blue is responsible for beginning to record the information
and for turning on the Launch Rev Limit. The Spool limit is activated when the Dark Blue and the Light Blue
wires are activated at the same time (applied to 12 volts).
The Dark Blue wire must always be removed from 12 volts after the Light Blue wire is removed from 12
volts.
In order to reset the Run History you must be sure that the Light Blue wire is switched to 12 volts, then
removed. If this wire receives 12 volts during a pass, recording of the History will be stopped.
The Dark Blue wire arms the History Recording function when it is applied to 12 volts. When the 12 volts
are removed, it will begin recording, including the two seconds prior to the wire being removed (unless
the acquire program is set up to record on rev limit. See Acquire options on page 12.)
Having a reset switch for the History Record accessible to a crew person is a suggestion. This way, as
the car rolls into the lights the switch could be turned on and off to ensure that it is reset and ready to
record just before the car stages.
REV LIMIT WIRING THE SPOOL REV LIMIT
Many turbo cars use the Burnout limit when prestaged to build up boost pressure prior to going into the
staged beam where the Launch Rev Limit is activated. MSD added a fourth rev limit, the Spool Limit, that
can be used to help the car spool up boost prior to doing a burnout. This limit is activated when both the
Light Blue and Dark Blue wires are connected to 12 volts.
Before the burnout - Supply 12 volts to the Dark Blue and Light Blue wires to activate the Spool Rev Limit.
Pre-Staged - Apply 12 volts to the Light Blue wire to activate a lower limit to begin spooling the turbo.
This can be activated through a switch on the brake pedal.
Staged - The Light Blue wire must be removed from 12 volts in order to enable the History Record
Function, and the Dark Blue must be applied to 12 volts to activate the Launch Rev Limit. This can be
accomplished by connecting the Dark Blue wire to the transbrake circuit and removing your foot from
the brake to deactivate the Light Blue wire.
Figure 4 Typical Wiring of Rev Limits. Figure 5 Launch Wiring for Clutch Cars.