Acura NSX 1997 Service Manual page 913

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Description ———————————————————————————————————————
Ignition Timing Control:
The programmed ignition used in this engine provides optimum control of ignition timing. A microcomputer determines
the timing in response to engine speed and manifold vacuum pressure. The input signals are transmitted by the crank-
shaft position/cylinder position (CKP/CYP) sensor, throttle position (TP) sensor, ECT sensor, and MAP sensor. This sys-
tem, not dependent on a governor or vacuum diaphragm, is capable of setting lead angles with complicated characteristics
which cannot be provided by conventional governors or diaphragms.
Basic Control
Determination of ignition timing/current duration:
The ECM has stored within it the optimum basic ignition timing for operating conditions based upon engine speed and in-
take manifold pressure. With compensation by signals from sensors, the system determines optimum timing for ambient
conditions and sends voltage pulses to the ICM.
Compensation of Ignition Timing:
Compensation Item
Idling
Compensation at warm-up
Engine coolant
temperature compensation
Control at Start
Ignition timing is fixed at 5° BTDC for cranking. The cranking is detected by the CYP sensor (cranking rpm) and starter signal.
Misfiring Detection
As part of the OBD II misfiring detection system, each of the ignition coils has a built-in spark plug voltage sensor. This
sensor detects the long duration high voltage which occurs in case of unfavorable combustion or misfiring. (For details,
see section 11.)
Table of Contents
Related Sensor and Information
CKP/CYP sensor, MAP sensor
Engine coolant temperature
(ECT) sensor
ECT sensor
Description
Ignition timing is controlled to the target speed
with compensation according to the idling speed.
Lag angle is adjusted according to warm-up con-
ditions to bring about a good balance between
operating performance and exhaust gas level.
Compensation for lead angle at low coolant
temperature and lag angle at high coolant
temperature.