Haltech E6K - Manual (Page 130)

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recommended if the desired flow is more than 20% than the system currently achieves. Fuel
flow is not in direct proportion to fuel pressure. Increasing fuel pressure will increase injector
dead time and reduce the flow rate of the pump.
D.3 Injector Staging
Another way of increasing injector flow, without compromising good drivability and fuel
economy is to employ staged injection. Injector staging allows the use of primary and
secondary injectors and is usually only used on high boost turbo or supercharged engines. The
ECU will fire only the primary set of injectors until a preset load point, where the ECU will
control both primary and secondary injectors.
The turn on point for the secondary injectors depends on injector size and engine
performance, but will usually occur just after the pressure in the intake manifold of the engine
has reached atmospheric pressure. Typically bar number 14 to 16 will work well in most
applications. The staging point must occur before the primary injectors have reached 100%
duty cycle. Go to the highest speed range in the fuel map that the engine is using, and make
sure that the last bar for primary injection is not too high. If it is, you must stage at a lower
pressure. (Refer to section 4.8 Duty Cycles).
Adjust the bars around the staging point with extreme care to ensure that the engine does not
lean out as the secondary injectors come in. When the Haltech ECU begins to stage it begins
firing both sets of injectors at once and fires them with the same duration. This means that if
both primary and secondary injectors are of the same flow rate then the first staged bar should
theoretically be slightly more than half that of the last un-staged bar. Allow a safety margin by
using 60% of the last bar.