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

INSTALLATION INSTRUCTIONS 7
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capabilities. At lower rpm, there are less revolutions per second so the Margin should be set lower. At
high rpm there are more combustion events taking place as well as more mechanical variables (such
as crank flex) so the high Margin should be set higher.
Low: Default is 200 rpm.
High: Default is 400 rpm.
LAUNCH SLEW
This controls the status of the Slew Rev Limiting feature.
SlewOff: Activates the Slew Rev Limiting feature. Default is Off.
Inhibit: This feature allows you to inhibit the activation of the Slew for an adjustable length of
time after the launch. It is adjustable from .02 - 5 seconds in 20ms increments.
TARGET
HoldCnt: The number of cylinder counts that occur after a Slew rev limit is active before the
Slew Target rpm is repositioned. The default is 10 which is typical for an engine in the 7000-
8000 rpm range.
Higher revving engines should use a higher Hold Count. A pro stock engine typically will be
set around 11 or higher. The count is adjustable from 1-99 and is most effective in the 5-20
range.
LIMIT CNT
The Limit Count will set a maximum number of Rev Limits by the Slew Rate Rev Limiter. Adjustable
from 0-500 maximum, in increments of 2.
Note: Reviewing the Launch History will help set the Target and Margin settings.
START RETARD
Program an amount of retard that will occur while the engine is cranking. This helps reduce the load
on the starter for easier cranking. It is adjustable from 0° - 25° in 1° increments. This is an automatic
feature and will enable below 500 rpm and will deactivate when the engine reaches above 800 rpm.
Default is 10°.
LAUNCH RETARD
This is the time based retard ramp. It can be programmed from 0°-15° in 0.1° increments and from
0-2.5 seconds. When the Dark Blue Launch/Reset wire is connected to 12 volts, the retard value is
activated and is added to the retard sum. When 12 volts are removed from the Dark Blue wire, the
retard value begins to ramp up to 0° over the programmed time. Once the time is over, the retard will
not be activated again.
STEP RETARDS
There are three step retards that are controlled through three corresponding activation wires or through
rpm. They can also have an rpm point that the engine must reach before the retard becomes active.
(A minimum rpm can also be programmed that must be reached before a step becomes active.) A
time based ramp can be programmed to gradually bring the retard to its full On amount, or to ramp
the retard amount out (back to no retard) from its setting.
Step 1 – Pink Step 2 – Violet Step 3 – Tan
Note: These wires can also be used as Gear Select Indicators. See page 9.
Activation through Wiring: Each step is activated when 12 volts are applied to its
corresponding wire. When the steps are enabled at the same time the retard amounts are