EFI - Functions of Engine EC
U
-RELEVANT SIGNALS
• Throttle position (IDL)
• Engine
speed (NE
)
• Coolant temperature (THW)
• Stop lamp switch (STP
)
- REFERENC
E
1
. In some manual transmission models, the
clutch switch (N/C) signal is also used as a
condition for fuel cut-off
.
2
. There are some models in which the fuel
will be cut off when the injection volume
during deceleration falls below the predeter-
mined level even if the throttle valve is not
completely closed (idle contact off)
.
i
b
. Fuel Cut-Off at High Engine Speed
s
To prevent engine over-run, fuel injection is
halted if the engine speed rises above a
predetermined level
. Fuel injection is resumed
when the engine speed falls below this level
.
RELEVANT SIGNA
L
• Engine speed (NE
)
c
. Fuel Cut-Off at High Vehicle Speed
s
In some vehicles, fuel injection is halted if the
vehicle's speed exceeds a predetermined level
.
Fuel injection resumes after the speed drops
below a predetermined level
.
- RELEVANT SIGNAL
• Vehicle speed (SPD
)
IYV I
C
The Engine ECU also performs various other
corrections in addition to these (page 72 to
79)
.
3 Voltage correctio
n
There is a slight delay between the time that the
Engine ECU sends an injection signal to the
injectors and the time that the injectors actually
open
. This delay becomes longer the more the
voltage of the battery drops
. This means that
the length of time that the injector valves
remain open would become shorter than that
calculated by the ECU, causing the actual air-
fuel ratio to become higher (i
.e
., leaner) than
that required by the engine, if this were not
prevented by voltage correction
.
In voltage correction, the ECU compensates for
this delay by lengthening the duration of the
injection signal by a period corresponding to the
length of the delay
. This corrects the actual
injection period so that it corresponds with that
calculated by the ECU
. (The amount of this
correction value depends on the engine model
.
)
Voltage correctio
n
Off
Ope
n
Closed
Injector
actually open
OHP
68
0
I
----------------------------
Standard
operating
delay tim
e
Low
-
14
-
High
Ba
tt
e
ry
voltage (V)
OHP 5
8
RELEVANT SIGNA
L
• Ba
tt
e
ry
voltage (+B)
Injection
signa
l
~
79
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