Staged Injection

Staged injection allows the use of one set of small injectors for low-load and/or low RPM operation of the engine with the ability to engage a second set of injectors at higher load and RPM when the primary set of injectors would otherwise reach their maximum operational duty cycle. The MSIII's staged injection function supports staging equally between the primary injectors and secondary injectors during staged operation as well as staging completely to the secondary set of injectors.

Staged Injection Behavior in Upgrade Mode

In Upgrade mode, all primary injectors should be connected to injector channel 1, and all secondary injectors should be connected to injector channel 2.

Staged Injection Behavior in MS3X Mode

In MS3X mode, When used with a 4 cylinder (or less) engine, The primary injectors are injector channels A through D, and the secondaries are channels E through H, or optionally, the secondaries can be connected non-sequentially to the mainboard channels 1 and 2. If connected to channels 1 and 2, the secondaries will run in "2 squirts alternating" configuration.

If used with more than 4 cylinders, the secondaries will automatically run on the mainboard channels 1 and 2 in "2 squirts alternating" configuration.

Staged Injection Behavior in MS3X Sequential Mode

In MS3X Sequential mode, the same output guidelines apply as in MS3X non-sequential mode except that in the case that the secondaries can be connected to the MS3X outputs, they run fully sequential, and if they are connected to the V3 board, they run semi-sequential.

Additionally, the Secondary Injection Timing Table is enabled (in addition to the standard injection timing table) when using staged injection, so the user must remember to tune secondary injection timing separately from primary injection timing.

Staged Injection Settings

This section describes the all the settings associated with staged injection.

• Staged Injection First Parameter - This setting enables staged injection and sets the primary staging parameter, which is used to determine when to engage the secondary injectors. This setting includes the following options:
  • Off - Staging disabled.
  • RPM Stage at a specific RPM.
  • MAP Stage at a specific MAP.
  • TPS Stage at a specific throttle position.
  • Duty Stage at a specific primary injector duty cycle.
  • Table Stage based on the table included in the dialog.

    For table-based staging, 0% means not staged at all, and 100% means fully staged. Anywhere between 0% and 100% means partially staged. The firmware calculates the primary and secondary pulse-widths based on the injector sizes specified elsewhere in the dialog.

• Primary Injector size (cc) - Size of primary injectors in cubic centimeters.
• Secondary Injector size (cc) - Size of secondary injectors in cubic centimeters.
• Transition fully to secondaries - This setting is used to determine whether the fully staged state means that the primary and secondary pulse-widths are equal, or if the fully staged state means that primaries are shut down completely and staging transitions fully to the secondary injectors. The following settings are possible:
  • Off - The fully staged state means that the primary and secondary injector pulse-widths are equal.
  • On - The fully staged state means that the primaries are shut down, and staging transitions fully to the secondary injectors.
• Secondary Outputs - This setting controls whether the MS3X outputs are used for secondaries or the V3 board outputs are used. This option is only available with 4 or less cylinders. The following options are possible:
  • Use MS3x (if possible) - Use the MS3x board outputs if it is possible to do so.
  • Use V3 - Use the V3 board outputs.
• Secondary V3 Alternate - This setting controls whether the secondaries (when using the V3 board outputs) alternate between injector channel 1 and injector channel 2, or inject simultaneously on injector channel 1 and injector channel 2. The following settings are available:
  • Alternating (2 squirts) - Alternate between injector channel 1 and injector channel 2. Note that when in alternating mode, the firmware injects 2 squirts per cycle.
  • Simultaneous (1 squirt) - Squirt fuel on injector channel 1 and injector channel 2 simultaneously. Note that when in simultaneous mode, the firmware injects 1 squirt per cycle.
• Gradual Transition - This setting enables the ability to gradually reduce the pulse width of the primary injectors and gradually increase the pulse width of the secondary injectors as staged injection engages. This setting is most useful when the secondary injectors are located far away from the primaries on the intake tract. Gradual transition and associated settings are not available when using table-based staged injection. The following settings are available:
  • On - Gradual staging is enabled. The associated settings will be used to control how quickly the secondaries are engaged.
  • Off - Gradual staging is disabled. When staged injection engages, the pulse width will go immediately to the fully staged width.

• Transition events (ign events) - This setting is used when Gradual staging is enabled to determine how many ignition events it will take to go from no staging to fully staged.
• Primary reduction delay (ign events) - This setting is used to delay the reduction of the primary pulse width by the number of ignition events after the secondaries start coming online. It is only enabled when the gradual transition feature is enabled.
• Secondary Enrichment (ms) - This setting is used to inject more fuel on the secondaries than the fully staged calculation determines. This is useful when there is a small lean spot just after staged injection fully engages. This setting is only available when the gradual transition feature is enabled.
• Primary staging threshold (units) - This setting is used to determine when staged injection engages when using RPM, MAP, TPS, or Duty. It is not available when using table-based staging.
• Primary staging hysteresis - This setting is used to determine when staged injection shuts off. For example, if RPM is selected as the staged injection first parameter, and the primary staging threshold is 4100, and the primary staging hysteresis is 300, then staged injection will shut off the secondaries and return the primaries to their normal pulse width at 3800 rpm. This setting is not available when using table-based staging.
• Second parameter - This setting is used to add a second method for determining when to stage. The following settings are available:
  • Off
  • RPM
  • MAP
  • TPS
  • Duty

  Note that this setting should not be set the same as the first parameter setting. This setting is not available with table-based staging.

• Secondary staging threshold (units) - This setting determines the RPM, MAP, TPS, or Duty at which the secondary staged parameter allows staged injection to engage. This setting is not available unless a second staging parameter is enabled.
• Secondary staging hysteresis (units) - This setting is used with the secondary staging threshold setting to determine when staged injection will shut off. This setting is not available unless a second staging parameter is enabled.
• 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.

Tuning Staged Injection

It is recommended that on any setup with secondaries placed further up the intake tract than the primaries, table-based staging is used. It is possible to achieve a much smoother transition to staged injection in all situations when tuning with this method.

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.

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 gradual 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.