®
EFI - Functions of Engine EC
U
2
. FUEL INJECTION DURATION CONTRO
L
The actual fuel injection duration is determined
by two things
: 1) the basic injection duration,
which is, in turn, determined by the intake air
volume and the engine speed
; and 2) various
corrections based on signals from the various
sensors
. (During engine starting [cranking],
however, fuel injection duration is determined
differently, because the amount of intake air i
s
r- Sta
rt
ing injection contro
l
Fuel injection
duration control
' After-sta
rt
injection control
not stable during cranking . See page 70 for more
details
.) Corrections differ depending on the
engine model, because each respective engine
has its own characteristics to take into
consideration
.
The following table shows the main controls that
make up fuel injection control
:
Basic injection duration control
Intake air temp
. correction
Voltage correctio
n
Basic injection duration contro
l
Injection
correction
s
Voltage correctio
n
,,--
REFERENC
E
Fuel injection duration control consists of syn-
chronous injection, in which injection is per-
formed at a predetermined crankshaft angle as
described above as well as asynchronous injec-
tion in which injection is performed irrespective
of the crankshaft angle
.
Asynchronous injection consists of starting in-
jection control in which injection is performed
only once during cranking and acceleration in-
jection in which injection is performed only
once during acceleration
.
Synchronous
F
injectio
n
Fuel
injection
duration
control
Asynchronous
injection
Intake air temp
. correction
After-sta
rt
enrichment
Warm-up enrichmen
t
Air-fuel ratio correction during
transitio
n
Power enrichment
Air-fuel ratio feedback
correctio
n
CO emission control correction
Idling stability correction
High-altitude compensation
correctio
n
Fuel cut-of
f
Starting injection
~ contro
l
_After-start injection
contro
l
rStarting injection contro
l
L
Acceleration
injection
contro
l
68
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