Hyundai Sonata 1991 Shop Manual page 243

MPI SYSTEM
2. Sequential injection (Synchronous injection)
After the engine is started, the injectors are activated at the
exhaust stroke of each cylinder, one cylinder after another.
Injection is, therefore, synchronized to the signals of the
crankshaft angle sensor.
The No.1 cylinder signal is the standard reference signal for
sequential injection; thus, using this signal as the standard
reference, the cylinder for fuel injection is determined, and
the fuel injection occurs in synchronization with the crank-
shaft angle sensor signals.
For each cylinder, there is one injection for each two rota-
tions of the crankshaft, in the firing order 1-3-4-2.
No.1 cyL --,
n
TOC
signal 1,- ----, ' - _
Crank
angle signal
Cylinder
No.1
No.3
No.4
No.2
Com-
E'J1
Inlake
Com-
Com-
bustion
haus!
preSSion buslian
Com-
Com- ".,,~
Intake
Com-
pression
bustian
haust
pression
Intake
Com-
Com- E'."l(.j
Intake
pressIOn bustian
hausl
E' . ,J(.I
Intake
Com- Com-
E,-,,\:!
hawsl
pression bustian hausl
Injector Driving Time
Y310EOA
Llnjection
31YQ07
Injector activation occurs one time per cycle for each cylinder,
and the injector activation time (amount of fuel injection), which
is the theoretical air/fuel mixture ratio relative to the amount
of intake air, is called the basic activation time.
The ECU functions to, first of all, calculate this basic activation
time according to air-flow sensor (AFS) signals and crankshaft
angle sensor signals.
When starting (cranking) the engine, the map value* determined
by the engine coolant temperature sensor signal is used as the
basic driving time.
During the deceleration, the basic driving time is set at zero.
The injector driving time is obtained by making the following cor-
rections on the above-mentioned basic driving time.
*Map value: The map value is a value set in advance and stored
in the ROM inside the ECU.
o Oxygen sensor feedback correction (Closed loop control cor-
rection)
In normal operation (including idling) after engine warm up,
the air/fuel ratio is corrected to an ideal air/fuel ratio by
using oxygen sensor signals. The three-way catalytic
converter gives the best degree of purification at the ideal
air/fuel ratio.
31-18