FUEL INJECTION CONTROL OPERATION [ZJ, Z6]

Injection Timing

Synchronized fuel injection

• The crankshaft rotation is synchronized by each intake and exhaust stroke of the cylinders, and fuel injection is performed by the fuel injection timing and the injection amount corresponding to the input signals of the following sensors.

- ECT sensor

- IAT sensor

- CKP sensor

- MAF sensor

Non-synchronized fuel injection

• The crankshaft rotation is not synchronized and fuel injection is performed by the injection timing and injection amount as triggered by the input signals of the following sensors.

- ECT sensor

- IAT sensor

- TP sensor

- MAF sensor

Relation between synchronized and non-synchronized fuel injection

• If synchronized and non-synchronized fuel injection happen to occur together, fuel is injected by adding the fuel injection timing of both.

Injection time

Fuel injector energization time and operation conditions

• The fuel injectors cause an operation delay with the start of energization from the PCM. The PCM calculates the fuel injection time by adding the non-injection time (ineffective injection time) to the actual injection time (effective injection time), and energizes the fuel injectors for this time.

• The fuel injection time is based on the following formula:

Fuel injection time = effective injection time + ineffective injection time

- The fuel injectors cause a delay in operation due to a delay in the build-up of operation current from coil inductance with the start of energization, and by the mass of the needle valve and plunger, and spring resistance. This delay is the ineffective injection time.

- The non-injection time is affected by the change in battery voltage. Accordingly, the PCM sets the non-injection time according to the battery voltage.

- The fuel injector opening valve time which is the actual fuel injection time is called the effective injection amount.

Determination of effective injection time

Start zone

• Improved engine startability

• When engine speed is 500 rpm or less.

• Determined according to engine coolant temperature and engine speed.

Feedback Zone

• Improved fuel economy

• Improved exhaust gas purification

• During engine operation other than high load volume increase zone and engine start zone.

• During normal driving, the injection time is determined by the front and rear HO2S and sets to the theoretical air/fuel ratio.

High load volume increase zone

• Improved driveability

• Either the engine speed, charging efficiency or throttle valve opening angle is a fixed value or more.

• Corrections are added to the basic injection amount and the high load coefficient is calculated according to the engine speed, mass intake airflow amount and the throttle valve opening angle.

Excessive speed fuel cut zone

• Engine protection

• Engine speed is approx. 6,500 rpm or more

• When the following conditions continue for 2 min or more:

- Vehicle is stopped.

- Engine speed is 5,000 rpm or more.

- Engine coolant temperature is 110°C {230°F} or more.

Note

• The PCM determines that the driver continues to unintentionally depress the accelerator pedal.

• Fuel injection time is set to 0 (fuel cut).

Deceleration Fuel Cut Zone

• Improved fuel economy

• Prevents overheating of the catalytic converter

• When the engine conditions are as follows (5 s or more after shifting the selector lever to other than P, N, or R, and 10 s or more after engine start):

- Fully-closed throttle valve during deceleration (charging at fixed value or more)

- During driving under high load at engine speed of 1,000 rpm or more (mass airflow sensor normal)

• Fuel injection time is set to 0 (fuel cut).

Calculation method table for fuel injection time

Contents (Fuel injection time, calculation method, or determination method)			Control zone
Injection time at start		Set value according to engine coolant temperature (low engine coolant temperature→long injection time)	*
Basic injection time		Basic injection time = charging efficiency x fuel flow coefficient		*	*
Fuel cut		Fuel injection time = 0				*	*
Ineffective injection time		Set time according to injector performance	*	*	*
Volume increase correction after engine start		Purpose: Maintains stability of engine speed just after engine start Correction condition • Specified time according to engine coolant temperature directly after engine start Correction amount • Low engine coolant temperature→large correction • Low intake air temperature→large correction		×
Front HO2S Feedback correction		Purpose: Controls air/fuel ratio to theoretical air/fuel ratio Correction condition • When engine coolant temperature is at set value or more. Correction amount • Front HO2S electromotive force is approx. 0.45 V or more→volume decrease correction • Front HO2S electromotive force is approx. 0.45 V or less→volume increase correction		×
Rear HO2S Feedback correction		Purpose: Corrects feedback amount according to deterioration of front HO2S and catalytic converter Correction condition • When engine coolant temperature is at set value or more. • Engine speed is 500-4,000 rpm. • Charging efficiency is 9-90%. Correction amount • According to rear HO2S electromotive force→correction		×
D-range correction (ATX)		Purpose: Ensures engine speed stability during D-range shifting Correction condition • Throttle valve fully-closed and shifted into D range Correction amount • Low engine coolant temperature→large correction		×
High load volume increase correction		Purpose: Improved engine output, decrease of exhaust gas temperature Correction condition • According to engine speed when the throttle valve opening angle is the fixed value or more, otherwise, according to engine speed and charging efficiency. Correction amount • High engine speed, high charging efficiency→large correction			×
Warm-up volume increase correction		Purpose: When engine coolant temperature is low, maintains combustion stability Correction condition • While at set engine coolant temperature Correction amount • High charging efficiency, low engine coolant temperature→large correction		×	×
Acceleration/deceleration volume increase correction		Purpose: Corrects fuel injection retard during acceleration/deceleration to ensure drive stability Correction conditions • Acceleration/deceleration (change in amount of charging efficiency) is at set value or more. Correction amount • Low engine coolant temperature→large correction • Large acceleration/deceleration amount→large correction		×	×
Deceleration volume increase correction		Purpose: Ensures stability of engine speed during recovery from fuel cut Correction condition • Recovery from deceleration fuel cut Correction amount • High engine speed→small correction		×
Learning correction		Purpose: Corrects deviation in air/fuel ratio from changes due to aged deterioration of mechanical devices Correction condition • Under any condition except purge control Correction amount • Learning value based on average of feedback correction value		×	×

Fuel Cut

Sensor damage fuel cut

• To prevent engine damage from abnormal ignition due to a malfunction input of a cylinder identification or the engine speed signal.

• DTC stored for the following devices:

- CKP sensor

- CMP sensor

Dechoke Control

• To improve engine starting startability when spark plugs are flooded.

• When cranking close to fully-open throttle valve

Fuel Cut During Immobilizer System Activation

• To prevent vehicle theft

• When an engine stop request signal is received from the immobilizer system, the PCM force-stops the fuel injectors. Therefore the engine stops.