FUEL INJECTION CONTROL OPERATION [F2]
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Fuel Injection Time
Control outline
• The PCM controls the fuel injection time to obtain the optimum air/fuel stoichiometric mixture ratio at all engine operation ranges according to engine operating condition.
Fuel Injection Timing
Control outline
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• There are two types of injection timing, “synchronized timing” and “non-synchronized timing”. With synchronized timing, fuel is injected at the preset crankshaft position. With non-synchronized timing, fuel is injected when certain conditions are satisfied regardless of the crankshaft position.
• When both synchronized and non-synchronized injections are required, both injections will be carried out on each specified timing. If the timing overlaps, injection will be carried out for their total time.
Synchronized injection
• There are the following types of synchronized control.
1 injection/1 ignition pulse:
Fuel is supplied by simultaneously providing one injection per SGT signal (four injection per cycle) to all cylinders. One injection period supplies a quarter of the fuel necessary for ideal combustion.
1 injection/1 crankshaft rotation (two-group injection)
Fuel is supplied to all cylinders simultaneously by giving one injection per crankshaft rotation (one injection per cycle). The determination for two-group injection is made by the SGT signal of the No.2 cylinder created in the distributor.
Non-synchronized injection
• There are the following types of non- synchronized control.
Idle non-synchronized control
• When the CTP switch is turned off, all cylinders are simultaneously injected for a certain period of time according to the engine coolant temperature.
Throttle non-synchronized
• When the throttle opening angle variation rate exceeded a specified value, fuel is simultaneously injected to all cylinders for a certain period of time according to the engine coolant temperature.
Control Zones
Operation outline
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• The PCM controls effective injection time by dividing engine operating condition into five zones to control balanced air/fuel stoichiometric mixture ratio according to the engine and load conditions.
Start zone
• The purpose of this zone is to improve startability
• The start zone corresponds to an engine speed of less than 500 rpm.
• The final fuel injection amount in start zone is determined according to the engine coolant temperature and engine speed.
Excessive speed fuel cut zone
• The purpose of this zone is to protect the engine.
• Excessive speed fuel cut zone is when the engine speed is above 5,800 rpm for over 5 s or above 6,100 rpm.
• Fuel injection resumes when the engine speed has dropped below 5,700 rpm.
Deceleration fuel cut
• The purpose of this zone is to improve fuel economy and to prevent overheating of the TWC.
• In deceleration fuel cut zone, fuel injection is stopped when braking with loaded idling, engine speed above 1,300 rpm, and engine coolant temperature above 80 °C {176 °F}.
Heavy load volume increase zone
• The purpose of this zone is to improve drivability under heavy load condition.
• The heavy load volume increase zone is when charging efficiency is high with throttle opening angle more than preset value or engine speed is above 4,000 rpm.
• The fuel injection time for the heavy load volume increase zone is calculated using the following formula:
Fuel injection time = High altitude volume increase correction × Warm-up volume increase correction ×
Acceleration increase correction × Heavy load volume increase correction ×
Learning correction
• The heavy load volume increase correction is operated only in the heavy load volume increase zone.
Closed loop zone
• The purpose of this zone is to improve fuel economy and to reduce exhaust emission level.
• The control system is in the closed loop zone when it is in other than the above zones.
• The fuel injection time for the closed loop zone is calculated the following formula:
Fuel injection time = High altitude volume increase correction × (Warm-up volume increase correction +
Idle (load) volume increase correction + Idle (no load) volume increase correction) ×
Acceleration increase correction × Deceleration volume decrease correction ×
(Closed loop correction × Learning correction)
• The closed loop correction is operated only in the closed loop zone.
Corrections
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Correction
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Purpose
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Condition
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Action
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Volume increase correction after start
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To maintain engine speed stability after start
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Certain period after start determined by ECT
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Lower ECT → Larger correction
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Warm-up volume increase correction
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To maintain drivability during warm-up
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According to ECT
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Lower ECT → Larger correction
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Acceleration volume increase/deceleration volume decrease correction
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To maintain engine response during acceleration and drivability during deceleration
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According to ECT
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Lower ECT → Larger correction
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Closed loop correction
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To control air/fuel stoichiometric mixture ratio close to stoichiometric
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When control is in closed loop zone
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—
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Learning correction
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To deal with change in air/fuel stoichiometric mixture ratio caused by aging
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At all times
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—
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Heavy load volume increase correction
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To maintain drivability under heavy load
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According to engine speed and charging efficiency when throttle opening angle more than preset value
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High engine speed → Larger correction
Larger charging efficiency → Larger correction
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Idle (load) volume increase correction
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To maintain engine speed stability with load at idle
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According to engine speed when idling under loaded condition with ECT more than 20 °C {68 °F} (in closed loop zone)
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High engine speed → Larger correction
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Idle (no load) volume increase correction
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To maintain engine speed stability with no load at idle
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When idling with engine speed below 1,000 rpm
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When idling with engine speed below 1,000 rpm → Set amount of correction
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High altitude volume increase correction
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To adjust air/fuel ratio according to air density change at high altitude
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When air pressure below 93 kPa {694 mmHg, 27 inHg}
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High engine speed → Larger correction (Decreases when engine speed exceeds 3,000 rpm)
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Fuel Cut Control
Dechoke control
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Outline
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• Dechoke control executes fuel cut to improve startability when the spark plug becomes fouled because of flooded engine.
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Operation
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• Fuel injection is cut if the throttle valve is held at wide open throttle during cranking (engine speed below 500 rpm).
