Honda Acura NSX 1991 Service Manual page 1075

Description
ignition Timing Control:
The programmed ignition (PGM-IG) employed in this engine provides optimum control of ignition timing by determining
the optimum timing using a microcomputer in response to engine speed and vacuum pressure in the intake manifold,
which are transmitted by signals from CRANK/CYL
sensor. This system, not dependent on a governor or vacuum diaphragm, is capable of setting lead angles with compli-
cated characteristics which cannot be provided by conventional governors.
Battery voltage
MAP sensor
Thottle angle sensor
Coolant temperauture
sensor
Basic Control
Determination of ignition
The control unit has stored within it the optimum basic ignition timing for operating conditions based upon engine speed
and intake manifold pressure. With compensation by signals from sensors, the system determines optimum timing for
ambient conditions and sends voltage pulses to the igniter unit.
Compensation of ignition timing:
Compensation Item
lding
Compensation at
warm-up
Coolant temperature
compensation
Control at Start
Ignition timing is fixed at BTDC 15" for cranking. The cranking is detected by the CYL sensor (cranking revolution) and
starter signal.
sensor, throttle angle sensor, coolant temperature sensor and MAP
Voltage compensation
Current duration
Idling compensation
Coolant temperature compensation
Compensation at warm-up
timing/current duration:
Related Sensor and Information
MAP sensor
Coolant temperature sensor
Coolant temperature sensor
PGM-FI ECU
Compensation
Compensation
Ignition timing is controlled to the target speed
with compensation according to the idling speed.
Lag angle is adjusted in accordance with the
warming up conditions to bring about a good
balance between
exhaust gas level.
Compensation for lead angle at low coolant
temperature and lag angle at high coolant
temperature.
DIRECT
IGNITION
SYSTEM
Igniter unit
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Ignition coil
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Description
operating performance and
23-89
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II
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