7.3 Ignition Settings 7 ADDITIONAL ITEMS: BEYOND BASIC FUEL AND IGNITION CONTROL
• Off duty - The duty cycle to command when the fuel pump is deactivated.
• Minimum duty - The lowest duty cycle that produces fuel flow. 0% for most applications, but Ford FPDM
modules often need this set to 5%.
• Maximum duty - The highest duty cycle to command. Most applications will go to 100%, but Ford FPDM
modules need this set to 50%.
• Pressure sensor input - enables a fuel pressure sensor signal. Required if using closed loop PWM. Used
for correction on other modes.
• Sensor type - MS3Pro supports many different fuel pressure sensor types.
– Gauge - The sensor is referenced to atmospheric pressure, and read zero with no fuel pressure. With a
vacuum referenced regulator, the reported pressure will drop under vacuum and increase under boost.
– Absolute - These sensors are referenced to absolute vacuum, and read about 14.7 psi when there is no
fuel pressure.
– Differential - Differential sensors are referenced to manifold pressure, and will read a constant value
when the fuel pump is on if everything is working correctly.
• Temperature sensor input - Allows using a fuel temperature sensor.
• Temperature correction - If using a fuel temperature sensor, turns on a temperature correction curve.
• Closed loop PID settings - Changes the sensitivity of the closed loop PID control.
7.2.14 Fuel pressure safety
This table is enabled if you have configured a fuel pressure sensor under Fuel Pump and Pressure Control.
Fuel pressure safety is a failsafe feature that allows shutting down the engine in the same way as AFR Safety
if the fuel pressure goes out of range. You can specify what RPM and load to use when checking, as well as the
maximum allowable pressure drop and how long this can continue before triggering a shutdown.
7.3 Ignition Settings
7.3.1 Dwell battery correction
The dwell battery correction/adjustment curve is a built-in curve to automatically apply greater spark dwell at lower
battery voltages. This is required for inductive ignition systems - more time is required to charge the coil with less
voltage. The default curve as shown is suitable for most applications. Note that it is centered on 14.4V with 100%
- at this voltage the actual dwell time matches the dwell entered on the ignition options page.
7.3.2 Dwell vs RPM
The Dwell vs. RPM curve is a feature intended to be used with Saab Tri-ionic ignitions only. These require "Time
After Spark " to be enabled. The dwell vs. RPM curve must also be turned on under the Ignition Options / Wheel
Decoder mode, as shown below:
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 165
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