7.2 Fuel Settings 7 ADDITIONAL ITEMS: BEYOND BASIC FUEL AND IGNITION CONTROL
• Secondary staging logic - This setting is used to determine whether both the primary and secondary
staging parameters must be met to engage staged injection, or if only one of the parameters must be met.
This setting is not available in table-based staging mode.
• Relay Output - Allows using a relay to power secondary injectors in systems where the primary and sec-
ondary injectors are both wired to the same ECU output pin, with the secondary injectors receiving switched
power from a relay. This tends to produce a jerky, abrupt transition, and is mainly in place to support plug
and play applications where the factory wiring lacks separate outputs for primary and secondary injectors.
• Relay Output Polarity - If set to normal, turning the output on turns on the secondary injectors. Inverted
turns this off to activate the secondary injectors.
• Pre-Relay Output - Allows activating a relay before the secondary injectors are active. This is usually to
allow a secondary fuel pump to pressurize the second stage injector rail.
• Pre-Relay Output Polarity - If set to normal, the pre-relay is turned on before turning the injectors. If set to
inverted, the pre-relay output is set to off before turning on the secondary injectors.
• Pre-Relay Timer - Specifies the time, in seconds, between turning on the pre-staging relay and the sec-
ondary injector stage.
7.2.3.1 Tuning Staged Injection Our recommendation is that on any setup with secondaries are further up the
intake tract than the primaries, that you should use table-based staging. It is possible to achieve a much smoother
transition to staged injection in all situations when tuning with this method.
7.2.3.2 Tuning Table-based Staged Injection The following tips should be followed when tuning table-based
staged injection:
• RPM and Load transition bins - Make the two RPM bins and two Load bins where staged injection first
engages close together. Also make the staging percent jump to 10-20% almost immediately (as shown in
the dialog at the beginning of the staged injection section). This is so that a very small amount of time is
spent with the secondary injectors at or near the injector opening time for those injectors. Spending a lot
of time near the injector opening time can lead to inconsistent fueling, especially if the secondary injector
opening time has not been determined and the default value is being used.
• Transition to 100% engaged - The transition to 100% engaged should be determined using experimentation.
In general, the transition should be set so that the primaries stay close to their maximum duty cycle (80%
is recommended) for as long as possible. This ensures that reduction to the primary pulse-width does not
result in a lean situation. The table displayed at the beginning of the staged injection settings section is a
good example of how to tune table-based staging for a smooth transition on a naturally aspirated engine.
7.2.3.3 Tuning All other Staged Injection Modes All staged injection modes that do not use the table to
determine the staging amount can be tuned similarly. The following tips should be used:
• Primary staging parameter - It is usually recommended that the primary staging parameter used is Duty.
This ensures that staged injection engages when the duty cycle of the primary injectors warrants it instead
of trying to guess what RPM or load will cause use of the secondaries to be necessary.
• Secondary staging parameter - It is recommended that this parameter only be used with forced induction
engines. It should be used to ensure that staging is fully complete before going into boost so that any lean
spots caused by staging are gone.
• Gradual transition - The gradual transition code was introduced to try to solve the same problems that table-
based staging solves, notably the small lean spot in AFR briefly after staged injection engages. It should be
set to transition over as many ignition events as possible for the smoothest transition. If doing this still causes
a lean spot, the primary reduction delay can be used along with the secondary enrichment setting to make
sure that slightly more fuel than calculated using the normal fuel calculations is injected. If enabling the grad-
ual transition feature still does not get rid of the brief lean spot after staging is engaged, it is recommended
that table-based staging is used.
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 155
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