Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 82

0
FOR L-TYPE EFI
EFI - Functions of Engine EC U
This is the most basic injection duration, and is
determined by the volume of air being taken in
(VS, KS or VG signal) and the engine speed (NE
signal) . The basic injection duration can be ex-
pressed as follows :
Basic injection Intake air volume
duration =K x Engine spee d
where K : correction coefficient
-RELEVANT SIGNAL S
• Intake air volume (VS, KS or VG)
• Engine speed (NE)
2 Injection corrections
The Engine ECU is kept informed of engine
running conditions at each moment by means of
signals from various sensors . It then makes
various corrections in the basic injection
duration based on these signals .
INTAKE AIR TEMPERATURE CORRECTIO N
The density of the intake air will change
depending on its temperature . For this reason,
the Engine ECU must be kept accurately
informed of the intake air temperature (by
means of the intake air temperature sensor) so
that it can adjust the injection duration to
maintain the air-fuel ratio that is currently
required by the engine . For this purpose, the
ECU considers 20°C (68°F) to be the "standard
temperature" and increases or decreases the
amount of fuel injected depending upon whether
the intake air temperature falls below or rises
above this temperature .
This correction results in an increase or decrease
in the injection volume by a maximum of about
10% (for the Karman vortex type air flow meter,
this is about 20%) .
In case of hot-wire type air flow meters, since
the air flow meter itself outputs a signal that is
corrected by the intake air temperature, the in-
take air temperature correction is not
necessary .
,,-
ivv
I r-
Low
20
High
(68 )
Intake air temperature °C (°F )
-RELEVANT
SIGNA L
• Intake air temperature (THA)
OHP 5 5
72