Acura NSX 1991 Manual page 228

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PGM-FI System
System Description
PGM-FI System
The PGM-FI system on this model is a sequential multiport fuel injection system.
Fuel Injector Timing and Duration
The ECM contains memories for the basic discharge durations at various engine speeds and manifold pressures. The
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.
Throttle Valve Control
The ECM controls the throttle valve control motor based on accelerator pedal position, TCS control unit and various sig-
nals. The ECM also controls the idle control function, cruise control function, and other functions with the throttle valve
control.
Ignition Timing Control
• The ECM contains memories for basic ignition timing at various engine speeds and manifold pressures. Ignition timing
is also adjusted for engine coolant temperature.
• A knock control system is also used. When detonation is detected by the knock sensor (KS), the ignition timing is
retarded.
Other Control Functions
1. Starting Control
When the engine is started, the ECM provides a rich mixture by increasing fuel injector duration.
2. Fuel Pump Control
• When the ignition switch is initially turned on, the ECM supplies ground to the PGM-FI main relay that supplies
current to the fuel pump for two seconds to pressurize the fuel system.
• When the engine is running, the ECM supplies ground to the PGM-FI main relay that supplies current to the fuel pump.
• When the engine is not running and the ignition is on, the ECM cuts ground to the PGM-FI main relay which cuts
current to the fuel pump.
• Excellent engine performance is achieved through the use of VTEC (Variable Valve Timing and Valve Lift Electronic
Control System), intake air bypass control and discharge volume control of the fuel pump.
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