Pgm-Fi Control System; System Description; Electronic Air Control Valve; Air Conditioning Signal - Honda Acura NSX 1991 Service Manual

PGM-FI Control System

. System Description

INPUTS
MAP Sensor
TW Sensor
TA Sensor
Throttle Angle Sensor
Oxygen Sensors
Vehicle Speed Sensor
Ignition Timing Adjuster
Knock Sensers
A/T FI Signals
TCS Signals
Starter Signal

Alternator FR Signal

Air Conditioning Signal

A/T Shift Position Signal

M/T Neutral Switch Signal

M/T Clutch Switch Signal
Battery Voltage (IGN. 1)
Fuel Pump Terminal Voltage
VTEC Oil Pressure Switch
Signals
The ECU contains memories for the basic discharge durations at various
basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors
to obtain the final discharge duration.
Electronic Air Control
Electronic Air Control Valve (EACV)
When the engine is cold, the A/C Fompressor is on, the transmission is in gear (A/T only) or the alternator is charging, the ECU
controls current to the EACV to msintain correct idle speed.
Ignition Timing Control
is also adjusted for coolant temperature.
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A Knock Control System is also used. When detonation is detected by the knock sensor, the ignition timing is
retarded.
Other Control Functions
1 . Starting Control
When the engine is started, the ECU provides a rich mixture.
2. Fuel Pump Control
When the ignition switch is initially turned on, the ECU supplies ground to the main relay which supplies current to
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the fuel pump for two seconds to pressurize the fuel system.
When the engine is running, the ECU supplies ground to the main relay which supplres current to the fuel pump.
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When the engine is not running and the ignition is on, the ECU cuts ground to the main relay which cuts current
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to the fuel pump.
Excellent engine performance is achieved through the use of VTEC (Variable Valve Timing and Lift Electronic Con-
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trol System), intake manifold chamber control and discharge volume control of the fuel pump.
3. Fuel Cut-off Control
During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at
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speeds over 1,500 rpm.
Fuel cut-off action also takes place when engine speed exceeds, 8,300 rpm regardless of the position of the
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throttle valve to protect the engine from over-revving.
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ELECTRONIC CONTROL UNIT
Injector Timing and Duration
Electronic Idle Control
Other Control Functions
Ignition Timing Control
ECU Back-up Functions
Injectors
Main Relay (Fuel Pump)
Fuel Pump Relay
Check Engine Light
EACV
A/C Compressor Clutch
Igniter Unit
1
Purge Cut-Off Solenoid Valve
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EGR Control Solenoid Valve
Chamber Volume Control Solenoid Valve
Radiator Fan Relay
Engine Compertment Fan Relay
VTEC Spool Valves
TCS Control Signals
Relay