4-14 FI SYSTEM
ECM (FI CONTROL UNIT)
The ECM is located under the seat.
The ECM consists of CPU (Central Processing Unit), memory (ROM) and I/O (Input/Output) sections. The signal
from each sensor is sent to the input section and then sent to CPU. On the basis of signal information received,
CPU calculates the volume of fuel necessary for injection using maps programmed for varying engine conditions.
Then, the operation signal of the fuel injection is sent from the output section to the fuel injector.
The eight kinds of independent program maps are programmed in the ROM.
These eight kinds of maps are designed to compensate for differences of the intake/exhaust systems and
cooling performance.
LIGHT LOAD: When the engine is running in a light load, the fuel injected volume (time) is determined the basis
of the intake air pressure and engine speed.
HEAVY LOAD: When the engine is running in a heavy load, the fuel injected volume (time) is determined the
basis of the throttle valve opening and engine speed.
INJECTION TIMING
The system employs a sequential, four-cylinder independent injection type, using the crankshaft position
sensor (signal generator) to determine the piston position (injection timing and ignition timing) and the cam-
shaft position sensor to identify the cylinder during operation, and these information are sent to the ECM. This
makes it possible to inject the optimum volume of fuel in the best timing for the engine operating conditions.
When the crankshaft begins to turn at the time of starting, the ECM sends the signals to the four injectors, #1,
#2, #3 and #4 to have them inject fuel simultaneously. From the second turn onward, the sequential four-
cylinder independent injection occurs as explained above.
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