Presentation - FuelTech Peak and Hold Manual De Instalación Y Operación

Peak and Hold

1. Presentation

In modern electronic injection systems, the electro valves, better known
as fuel injectors, are the parts responsible for injecting fuel into the
engine.
The fuel injector is a solenoid that works as a valve, freeing or blocking
the flow of fuel from the fuel line into the engine intake. The difference
between the fuel pressure and the manifold pressure (or wherever
the injector is located) makes the fuel to be atomized through the
EN
injector's orifice(s).
An injector may be fully open or closed. What determines the amount
of fuel injected is the time the injector stays open and closed at each
rotation cycle.
When the injection pulse is initiated, there is a short period of time in
which the injector's needle has not yet opened mechanically for fuel
flow, known as the injector "dead time".
Older fuel injectors as well as the modern high flow injectors feature a
heavier internal moving system, which requires a greater electric effort
to move the needle. Therefore, they have lower impedance (resistance
of the small internal coil) and need a greater electric current to be
driven. These injectors are the low impedance injectors and generally
feature less than 7Ω.
Modern injectors as well as the low flow injectors have a simpler
structure. Therefore, they need less energy to be driven and have
relatively high impedance, with no need of actuation current control.
A saturated high impedance fuel injector generally features between
7Ω and 20Ω.
The actuation of low impedance fuel injectors must be done through
an active current control, in which a greater current with maximum
power is applied until the needle opens mechanically ("peak" current).
Then, the current is limited to 25% of its initial value as to maintain
the injector open for the determined injection time (current to "hold"
the injector open).
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