Staged injection uses primary injectors operating all the time and secondary injectors which operate only at higher load/rpm. Both sets of injectors are controlled by the main fuel table (Fuel Table 1 and/or Fuel Table 2), however the percentage of the total fuel delivered by each injector set is controlled by the Secondary Injection Staging Table.
The secondary injectors may be brought on at any stage after the lockout conditions are met by entering non-zero numbers into the Secondary Injection table.
Setup Notes
·Staged Injection is visible only when the Injection Mode is set to Group/Staged, Sequential/Staged or Sequential/Multi-Point Group Staged.
·It is very important that BOTH the primary and secondary injector duty cycles are closely watched to ensure that neither set of injectors are being operated at an excessive duty cycle.
Staged Injection Settings
Determines how the fuel flow is split between the primary and secondary injectors. Options are:
It is recommended to use Sec/Pri Flow Ratio, especially if using modeled fuel (modeled won't work correctly with secondary extra as it is adding fuel on top of the calculated required amount).
·Sec/Pri Flow Ratio - The Sec/Pri Ratio setting determines the injection pulse widths of the primary and secondary injectors. Refer to the Sec/Pri Ratio setting for a detailed description.
·Secondary Extra - In this mode, primary injection pulse widths remain untouched, while secondary fuel is added as an addition. In this mode: Secondary Effective PW = Secondary Injection Table% x Primary Effective PW + Primary Effective PW. Note: this mode is being removed, please contact tech support if you need this mode.
In Sec/Pri Flow Ratio mode each injector is fired for some percentage of the Injection Effective PW.
With an Injection Effective PW of 10ms:
If the Secondary Injection Staging Table reads 25% - Primary injectors will have an effective PW of 7.5ms and secondary injectors will have an effective PW of 2.5ms.
If the Secondary Injection Staging Table reads 50% - Primary injectors will have an effective PW of 5ms and secondary injectors will have an effective PW of 5ms.
If the Secondary Injection Staging Table reads 75% - Primary injectors will have an effective PW of 2.5ms and secondary injectors will have an effective PW of 7.5ms.
In Secondary Extra mode, the primary injector will always fire for the Injection Effective PW time and the secondary injector time, some multiple of the Injection Effective PW.
With an Injection Effective PW of 10ms:
If the Secondary Injection Staging Table reads 25% - Primary injectors will have an effective PW of 10ms and secondary injectors will have an effective PW of 12.5ms.
If the Secondary Injection Staging Table reads 50% - Primary injectors will have an effective PW of 10ms and secondary injectors will have an effective PW of 15ms.
If the Secondary Injection Staging Table reads 75% - Primary injectors will have an effective PW of 10ms and secondary injectors will have an effective PW of 17.5ms.
This setting is only available when Staging Mode is set to Pri/Sec Flow Ratio.
The Sec/Pri Ratio is ratio of the total secondary injector flow to that of the primary injectors. This number must be entered before tuning. If primary and secondary injector flow rate is unknown it will be necessary to determine these either from injector specifications or on an injector flow bench. To calculate the correct number to enter as the Sec/Pri Ratio, divide the total secondary injector flow rate by the total primary injector flow rate. Total flow rate means the sum of all primary injector flows and sum of all secondary injector flows.
If the Sec/Pri Ratio is set too high then the engine will run leaner as the secondary injectors are activated. If the Sec/Pri Ratio is set too low then the engine will run richer as the secondary injectors are activated.
Example:
If an engine has four 240 cc/min primary injectors and two 650 cc/min secondary injectors then the Sec/Pri Ratio is calculated as follows:
·Total primary injector flow rate is 4 x 240 = 960 cc/min.
·Total secondary injector flow rate is 2 x 650 = 1300 cc/min.
·Sec/Pri Ratio is 1300 / 960 = 1.354.
The Sec PW Lockout is the minimum pulse width that the ECU will use for the secondary injectors (including the short pulse width adder but not including the deadtime). If the ECU calculates a required secondary pulse width that is below this then the secondary injectors will stay off and all fuel will be delivered by the primary injectors (including the fuel that was calculated for the secondary injectors). Once the ECU calculates a pulse width greater than the Sec PW Lockout value, fuel will be delivered through the primary and secondary injectors.
In some applications the primary and secondary injectors are physically mounted in different locations. Often the primary injectors will be mounted closer to the engine’s intake port with the secondary injectors further up the intake runner. If there is a large distance between the two injectors then the engine will run lean momentarily as the secondary injectors are activated. This occurs because the fuel delivered by the primary injectors has been reduced, but there is a delay in the secondary injector’s fuel reaching the engine.
Accel Fuel is the number of injection events (for each primary injector) after the secondary injectors become active that the primary injectors will inject the primary fuel volume + the same volume of fuel the secondary injectors are flowing (i.e. total fuel = primary + 2 * secondary). This is done to account for the time delay of the fuel coming from the secondary injectors reaching the inlet port. Values after the decimal point represent partial enrichments, for example a value of 2.5 when using sequential staged would result in the 3rd primary injection event being primary fuel volume + 0.5 * secondary fuel volume.
Staged Injection will not operate below this engine speed.
Secondary Injector Short Pulse Adder Table
Compensates for the non-linear flow characteristics of the secondary fuel injectors when at low pulse-widths. Functions the same as the primary Injector Short Pulse Width Adder Table.
Secondary Injector Dead Time Table
Specifies the secondary Injector Dead Time as a function of system voltage. Functions the same as the primary Injector Dead Time Table.
Determine the percentage of the total fuel flow which is delivered via the secondary injectors. This value can be changed depending on load.
·A value of 0% represents complete fuel delivery through the primary injectors. The secondary injectors will be off. Typically a value of 0% will be used at low load.
·A value of 50% results in half of the fuel being delivered by the secondary injectors.
·A value of 100% represents complete fuel delivery through the secondary injectors. The primary injectors will be off.
In typical applications the engine will run on the primary injectors at low load (0%). Often as load increases the Secondary Injection Table values will increase until the secondary and primary injectors operate at the same pulse width. Note that the Secondary Injection Table value required to give matched pulse widths depends on the size of the injectors in relation to each other.
The Secondary Injection Table value required to give equal pulse widths can be found by the following equation:
·Secondary Injection Table value for matched Pulse Width = (100 * Sec/Pri Ratio) / (1 + Sec/Pri Ratio)
Example:
The following example calculates the required Secondary Injection Table value to give equal primary and secondary injector pulse widths. Assuming the following information:
·Total Primary Injector Flow = 1100 cc/min.
·Total Secondary Injector Flow = 3200 cc/min.
·Sec/Pri Ratio = 2.9 (3200 / 1100 = 2.9)
Therefore the Secondary Injection Table required for matched pulse widths:
Table Value = (100 * Sec/Pri Ratio) / (1 + Sec/Pri Ratio)
= (100 * 2.9) / (1 + 2.9)
= 290 / 3.9
= 74.4 %
i.e. when the pulse widths are the same 25.6% of the fuel is delivered by the primary injectors, while 74.4% of the fuel is delivered by the secondary injectors.