7.8 Advanced Engine 7 ADDITIONAL ITEMS: BEYOND BASIC FUEL AND IGNITION CONTROL
• Fuel adder percent calc - When using progressive nitrous in a time based or VSS based mode, the added
fuel also needs to be scaled based on RPM. The MS3Pro will scale the “additional fuel PW” settings based
on either the nitrous duty cycle table or a separate fuel percentage table. For example, if the additional fuel
pulse width at minimum RPM is 6 ms, and the percentage table gives 75%, the added fuel pulse width will
be cut back to 4.5 ms.
Stage 1 settings:
• Stage 1 output - nitrous - Selects output pin to use for stage 1 nitrous solenoid
• Stage 1 output - fuel - Selects output pin to use for stage 1 fuel solenoid (These will normally be the same
for an on/off system, but may be different for progressive.)
• Enable input on: - Selects the input pin to use to enable the nitrous system. We recommend using the
digital 12 volt input pin for nitrous. If you’re using a conventional arming switch, this allows you to wire the
input to the nitrous solenoid power source.
• Additional Fuel PW @ N2O min rpm - In on/off mode with a dry system the fuel PW to add at the min rpm.
In progressive mode, this value is scaled down by either the nitrous duty curve or the fuel percentage curve,
depending on how you have set the “fuel adder percent calc” setting.
• Additional Fuel PW @ N2O max rpm - In on/off mode with a dry system the fuel PW to add at the max rpm.
When using progressive nitrous, this is scaled in the same way as the minimum RPM fueling. (In between
these two rpm points, the MS3Pro calculates the required pulsewidth using linear interpolation.)
• Retard Ignition by - In on/off mode sets a fixed ignition retard.
• Nitrous delay after launch - Sets a minimum time after launch control before nitrous can activate.
• Nitrous delay after flat shift - Likewise for flat shift.
• Allow nitrous during launch - Allows turning nitrous stage 1 on while launch control is activated to use
nitrous to build boost on a turbo car.
• Max MAP during launch - The nitrous system will turn off if MAP goes over this value and launch is active.
Stage 2 settings:
• Stage 2 output - nitrous - Selects output pin to use for stage 2 nitrous solenoid
• Stage 2 output - fuel - Selects output pin to use for stage 2 fuel solenoid
• Enable stage 2 above - In on/off mode, sets the activation rpm for stage 2.
• Max rpm - In on/off mode, sets the maximum rpm for stage 2.
• Delay after stage 1 - Sets a minimum time delay after stage 1 activates before stage 2 can activate. (To
prevent a massive hit.)
• Retard Ignition by - In on/off mode sets a fixed ignition retard for stage 2.
• Additional Fuel PW @ N2O min rpm - In on/off mode with a dry system the fuel PW to add at the min rpm.
• Additional Fuel PW @ N2O max rpm - In on/off mode with a dry system the fuel PW to add at the max rpm.
The progressive feature adds another level of control and complexity. The solenoid duty, added fuel and timing
retard for one or two stages can be plotted out against rpm or time giving you fine control over nitrous operation.
You’ll need to experiment to determine the best duty cycles. The way most solenoids work, 50% duty is rarely
equal to 50% flow. You will likely find that fuel and nitrous solenoids vary in behavior too (due to different coils and
liquid pressures, among other factors.)
As always, experimentation and careful testing, datalogging and refinement will be required to make the most
of this feature.
Progressive nitrous control will require using solid state relays to control the solenoids (see section 4.11.1 for
more information on solid state relays). The diagram below shows a nitrous system armed with a button connected
to Digital Switched In 1, using High Current Out 1 for the first stage and High Current Out 2 for the second stage.
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 250
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