Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 81

EFI - Functions of Engine EC U
AFTER-START INJECTION CONTRO L
When the engine is running at a more-or-less
steady speed above a predetermined rpm, the
Engine ECU determines the injection signal
duration as explained below :
Injection signal duration = basic injection
duration x injection correction* + voltage
correctio n
*Injection correction is the sum and product of
various correction coefficients .
Basic injection duration
• VS, KS, VG or PI M
• N E
Injection corrections
• TH W
• TH A
• PSW or VTA
• Other s
Voltage correction
• + B
Actual injection duratio n
Injection signal
OHP 55
1 Basic injection duratio n
FOR D-TYPE EF I
This is the most basic injection duration, and is
determined by the manifold pressure (PIM
signal) and the engine speed (NE signal) . The
internal memory of the Engine ECU contains
data on various basic injection durations for
various manifold pressures and engine speeds .
-RELEVANT SIGNALS
• Intake manifold pressure (PIM)
• Engine speed (NE )
REFERENCE
Since the intake efficiency varies depending on
the valve clearance, the intake air volume may
vary even if the intake manifold pressure stays
the same .
Therefore, in D-type EFI, when the valve
clearance varies, the air-fuel ratio of the air-fuel
mixture will change slightly .
• Since engines equipped with an oxygen sen-
sor correct injection duration according to
the air-fuel ratio feedback correction, the
air-fuel ratio is always maintained at the op-
timal level .
• In engines which are not equipped with an
oxygen sensor, the air-fuel ratio is adjusted
by a variable resistor (See page 41) .
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