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Injection Modes and Injectors
Chapter 5
73
Injection Modes and
Injectors
There are a number of ways to inject fuel, based on the
number of independent channels available to the ECM,
number and type of injectors, and the engine configuration.
Each mode has advantages and disadvantages depending
upon its application. The following general rule applies to them
all: the longer it takes to inject fuel, the better control you have
over it. It follows that if an injection mode allows a longer
injection time, it also offers better control. It also follows that
injectors should be sized according to the injection mode.
The fuel injection hardware operates independently of
software. The software calculates a pulse width or widths and
sends it to the injection hardware, which then drives the
injectors.
Synchronous and Asynchronous Injection
Synchronous injection means that the injection pulses are
timed to the ignition reference pulses in some fashion. That is,
they can be some multiple of reference pulses, or they can be
delayed from the start of the reference pulse. Synchronous
injection is normally used, except in the following
circumstances:
• When output pulse width becomes too small to be reliably
delivered.
• For transient acceleration modes, where fuel is required
instantly and not at the next injection pulse.
Vol 1, Chapter 5 Injection Modes and Injectors
73