Mazda X-5. Manual — part 36

CONTROL SYSTEM

01–40–17

01–40

Maximum Cam Retard Mode
Mode execution condition

• When any of the following conditions are met:

— Cranking

— Idling after completion of cleaning mode

— DTC stored for the following devices:

• ECT sensor

• CKP sensor

• CMP sensor

• TP sensor

• MAF sensor

• OCV

Purpose

• Maximum cam retard mode stabilizes engine speed by maximally retarding the valve timing when the engine

speed is low during idling.

Operation

• When the target current in the maximum cam retard mode is fixed at 100 mA. When 100 mA current is

supplied, the OCV opens the hydraulic passage for the retard chamber and hydraulic pressure from the oil
pump is introduced to the retard chamber. Because of this, the variable valve timing actuator is fixed at the
maximum retard position (minimum overlap).

Feedback Hold Mode
Mode execution condition

• Target valve timing and actual valve timing are almost the same.

Purpose

• The feedback hold mode holds the valve timing by returning the OCV spool valve to the neutral position when

target valve timing suitable for the engine operation conditions is obtained.

Operation

• Though the target current in the feedback hold mode is basically around 600 mA, feedback operation is

performed at all times so that the present OCV drive current approaches the target current. Because the hold
current changes due to mechanical variation between engines and deterioration due to aging on OCV internal
parts, the PCM continues to learn the changing current (hold current learning value) to maintain the spool valve
in the neutral position.

ADVANCE SPEED INCREASES
AS INCLINATION INCREASES

CHANGES ACCORDING TO MECHANICAL
VARIANCE AND AGED DETERIORATION

ADVANCE

RETARD

APPROX. 100 mA

APPROX. 600 mA

APPROX. 1,000 mA

OCV OPERATION CURRENT

E5U140ZT5101

CONTROL SYSTEM

01–40–18

Feedback Mode
Mode execution condition

• Except during cleaning, maximum cam retard, or feedback hold modes.

Purpose

• Feedback mode obtains valve timing suitable for engine operation conditions by performing the feedback

operation so that present OCV drive current is set closer to the target current determined by the PCM
according to engine operation conditions.

Operation

• Based on engine operation conditions, the target current is set between 100 mA (maximum retard) and 1,000

mA (maximum advance), using the neutral point of approx. 600 mA as a reference. Actually, the target current
is calculated by subtracting the current necessary for obtaining the target advance/retard amount, using a
reference at the hold-current learning value calculated from the neutral position of the spool valve.

Advance Spark Speed Correction

• If there is a large difference between the target valve timing and the actual valve timing, the target current

correction is applied so that it is set closer to the target valve timing more quickly to raise the advance spark
speed by advancing the spool valve initialization operation.

• The variable valve timing actuator advance spark speed increases as the hydraulic passage in the OCV widens

and decreases as it narrows.

Valve Timing Determination

• The PCM controls current to the OCV to obtain optimum valve timing suitable for the engine operation

conditions (target valve timing).

• The PCM compares target valve timing with actual valve timing, and feeds back the result to change valve

timing smoothly.

Target valve timing

• Determined according to engine speed and charging efficiency.

Actual valve timing

• Means present valve timing. Actual valve timing is calculated by adding the maximum cam retard learning value

for energization from the value detected by the CMP and CKP sensors.

Cam maximum retard learning value

• Though the intake camshaft valve timing (including maximum retard position) is detected based on the

difference between the signal from the sensor and signal from the CKP sensor, the difference between the
signals deviates due to the sensor installation condition. Because of this, the PCM stores the difference
between the signal build-ups at the maximum OCV retard position to prevent deviation in valve timing detection.

End Of Sie

FUEL INJECTION CONTROL OUTLINE [LF]

E5U014000000N25

• Performs optimum fuel injection according to engine operation conditions.

• The PCM determines the engine operation conditions based on the signals from the following input devices and

drives the injectors at the optimum fuel injection time (fuel injection amount) and the fuel injection timing to
inject fuel. For the construction/operation of the fuel injector, refer to “FUEL SYSTEM, FUEL INJECTOR
CONSTRUCTION/OPERATION”.

End Of Sie

CONTROL SYSTEM

01–40–19

01–40

FUEL INJECTION CONTROL BLOCK DIAGRAM [LF]

E5U014000000N26

End Of Sie

IAT SENSOR

MAF SENSOR

MAP SENSOR

CMP SENSOR

ECT SENSOR

CKP SENSOR

BARO SENSOR

NEUTRAL SWITCH (MT)

CPP SWITCH (MT)

BRAKE SWITCH

NO.1, NO.2

A/C AMPLIFIER

REFRIGERANT PRESSURE

SWITCH (MIDDLE)

REFRIGERANT PRESSURE

SWITCH (LOW, HIGH)

BATTERY

VEHICLE SPEED

SIGNAL

TR SWITCH (AT)

SYNCHRONIZED
FUEL INJECTION

EFFECTIVE
INJECTION TIME

INJECTION
TIME AT
ENGINE START

BASIC
INJECTION TIME

VARIOUS
CORRECTION
TYPES

INEFFECTIVE
INJECTION TIME

NON-SYNCHRONIZED
INJECTION CONTROL

INEFFECTIVE
INJECTION TIME

FUEL INJECTOR ENERGIZATION
TIMING AND ENERGIZATION
TIME

FUEL INJECTOR

PCM

FRONT HO2S

TP SENSOR NO.1, NO.2

APP SENSOR NO.1, NO.2

REAR HO2S

E5U140ZT5003

CONTROL SYSTEM

01–40–20

FUEL INJECTION CONTROL OPERATION [LF]

E5U014000000N27

Operation
Injection timing

• There is synchronized fuel injection, which performs fuel injection by the setting of the crankshaft position, and

non-synchronized fuel injection which performs fuel injection when the condition for fuel injection is met
regardless of the crankshaft position.

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.

— CKP sensor, MAF sensor, ECT sensor, IAT 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.

— TP sensor, MAF sensor, ECT sensor, IAT 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

• The PCM calculates the fuel injection amount according to the engine operation conditions as the fuel injection

time and energizes the fuel injectors.

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) with
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
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

Effective injection time

— The fuel injector opening valve time which is

the actual fuel injection time is called the
effective injection amount.

ON

OFF

0

INJECTION
SIGNAL

FUEL INJECTOR
CURRENT

FUEL INJECTOR

FUEL INJECTION TIME

INEFFECTIVE
INJECTION TIME

EFFECTIVE
INJECTION TIME

FUEL INJECTOR OPENING
VALVE ELECTRICAL
CURRENT

FUEL INJECTOR VALVE
OPENING TIME

OPEN

CLOSED

C3U0140S014