Subaru 2002 Impreza Service Manual page 52

GENERAL
Fuel lniection (Fuel System)
1.
General
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The Multipoint Fuel Injection (MFI) system supplies optimum air-fuel mixture under every engine
operating condition through the use of the latest electronic control technology.
This system pressurizes the fuel to a constant pressure and injects it into each intake air port in
the cylinder head. The injection quantity of fuel is controlled by an intermittent injection system
where an electro-magnetic injection valve or injector opens for a short period that is precisely con-
trolled depending on the quantity of air appropriate for each condition of operation. In actual con-
trol, an optimum fuel injection quantity is achieved by varying the duration of an electric pulse ap-
plied to the injector. This way of control enables simple, yet highly precise metering of the fuel.
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The engine control module (ECM) that controls the fuel injection system corrects the fuel injec-
tion amount depending on the vehicle speed, throttle opening, coolant temperature and other ve-
hicle-operation-related information. The ECM receives the information in the form of electric sig-
nals from the corresponding sensors and switches.
The MFI system also has the following features:
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Reduced exhaust emissions
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Reduced fuel consumption
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Increased engine output
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Quick response to accelerator and brake pedal operation
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Superior startability and warm-up performance in cold weather due to corrective controls made
according to coolant and intake air temperatures
FU-2