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GEN
INFO
FEATURES
Air-fuel ratio compensation equipment
An O
2
sensor is provided in the exhaust pipe upstream of the catalyst, to enable the catalyst to
operate at a high degree of efficiency. The O
2
sensor detects the level of concentration of the oxy-
gen remaining in the exhaust gases.
A high level of oxygen concentration signifies a lean air-fuel mixture, and when the O
2
sensor
detects this condition, it inputs a lean signal into the ECU. Conversely, when the level of oxygen
concentration is low, the O
2
sensor inputs a rich signal into the ECU.
The ECU system applies minute corrections to these signals so that the injection volume (the dura-
tion of the current applied to the injectors) comes to be within the vicinity of the stoichiometric ratio.
Thus, the system is designed to maximize the cleaning function of the catalyst.
Feedback compensation circuit
È
The ECU determines the basic injection volume based on the signals that are input from various sensors
and regulates the duration of the current applied to the injectors.
É
Current is applied to the injectors, enabling them to inject fuel.
Ê
The engine undergoes combustion and exhaust.
Ë
The O
2
sensor detects the level of oxygen concentration in the exhaust gases, and outputs a lean or rich
air-fuel ratio signal in accordance with the detected data.
Ì
In accordance with the signals from the O
2
sensor, the ECU applies minute corrections to the basic injec-
tion duration, determines the subsequent injection volume, and provides instructions to the injectors.
The above processes are repeated in order to maintain the mixture at the stoichiometric ratio.
Rich signal
Lean signal
Air-fuel ratio
judged as
lean
Air-fuel ratio
judged as
rich
Prolongs the duration of the current
applied to the injectors
Injection duration correction circuit
Shortens the duration of the current
applied to the injectors
Signal from
various sen-
sors
Injector
O
2
sensor
Basic injection duration circuit
Illustration is for reference only.