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Mazda CX-5 Service & Repair Manual: Fuel Injection Control System

Mazda CX-5 Service & Repair Manual / Engine / Control / Fuel Injection Control System

Outline

Block Diagram


Operation

Injection timing

Injection time

Determination of effective injection time

Control zone table

Control name

Control outline

Start zone

    Purpose

  • Improved startability

    Control condition

  • When engine speed is less than 500 rpm

    Determination of fuel injection time

  • According to engine coolant temperature and engine speed and fuel pressure

Feedback zone (? = 1)

    Purpose

  • Improved fuel economy

  • Improved exhaust gas purification

    Control condition

  • During engine operation condition except for engine start zone and feedback zone (? rich) and fuel cut zone

    Determination of fuel injection time

  • During normal driving, the various correction amounts are added to the basic injection time during normal driving to obtain a ratio that is close to the theoretical air/fuel ratio.

Feedback zone (? rich)

    Purpose

  • Improved driveability

    Control condition

  • The accelerator pedal opening angle is the specified value or more

    Determination of fuel injection time

  • Fuel amount increases according to accelerator pedal opening angle

    Purpose

  • Protection of catalytic converter and exhaust system components (suppression of gas temperature)

    Control condition

  • The estimated exhaust temperature and estimated catalytic converter temperature are the specified value or more.

    Determination of fuel injection time

  • Fuel amount increases according to estimated exhaust gas temperature and estimated catalytic converter temperature (promotion of cooling efficiency from vaporization heat)

Excessive speed fuel cut zone

    Purpose

  • Engine protection

    Control condition

  • When engine speed is 6,500 rpm or more

  • When engine speed is 2,500 rpm or more (When DTC P0089:00 is stored)

    Determination of fuel injection time

  • Fuel injection stopped.

Deceleration fuel cut zone

    Purpose

  • Improved fuel economy

    Control condition

  • If all of the following conditions are met while the vehicle is decelerating

    • Accelerator pedal is fully closed

    • Engine speed is specified value or more

    • Vehicle speed is specified value or more

    Determination of fuel injection time

  • Fuel injection is stopped.


Fuel injection time calculation method table

(A: Fuel injection time base, B: Correction for fuel injection time)

Contents

(Calculation or determination method for fuel injection time and correction)

Control zone






Injection time at engine start

Set value according to engine coolant temperature (low engine coolant temperature>long injection time)

A

Basic injection time

Basic injection time = Charging efficiency *1 ? fuel flow coefficient*2

? target equivalent

A

A

Fuel cut

Fuel injection time = 0

A

A

Ineffective injection time

Set time according to fuel injector performance

A

A

A

Volume increase correction at engine start

Purpose: Ensures engine speed stability 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

B

B

Feedback correction (A/F sensor)

Purpose: Controls air/fuel ratio to theoretical air/fuel ratio

    Correction amount

  • A/F sensor output current is 0 mA or less>volume decrease correction

  • A/F sensor output current is 0 mA or more>volume increase correction

B

B

Feedback correction (HO2S)

Purpose: Controls air/fuel ratio to theoretical air/fuel ratio

    Correction amount

  • HO2S output voltage is approx. 0.7 V or more>volume decrease correction

  • HO2S output voltage is approx. 0.7 V or less>volume increase correction

B

Warm-up volume increase correction

Purpose: Ensures combustion stability when engine coolant temperature is low

    Correction condition

  • When engine coolant temperature is at set value

    Correction amount

  • High charging efficiency, low engine coolant temperature>large correction

B

B

Learning correction

Purpose: Corrects deviation in air/fuel ratio from deterioration over time of mechanical devices

    Correction amount

  • Learned value based on average value of A/F deviation amount (feedback amount)

B

B

Heavy load volume increase correction

Purpose: Improved engine output, decrease of exhaust gas temperature

    Correction condition

  • Based on the fixed value when the accelerator pedal opening angle is a certain value or more, otherwise, based on engine speed and charging efficiency.

    Correction amount

  • High engine speed, high charging efficiency>large correction

B


*1 Charging efficiency is the ratio of the actual amount of intake air to the maximum air charging amount (mass volume) of the cylinder. The value increases as the engine load increases.

*2 Fuel flow coefficient is a coefficient to calculate a fuel injection time from a fuel injection amount required for an intake air amount.

Fuel cut

Fuel cut table


Control name

Control outline

Fuel cut during selector lever shifting in D range (ATX)

    Purpose

  • ATX protection

    Control conditions

  • When shifting while vehicle is stopped and engine raced

Sensor malfunction fuel cut

    Purpose

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

    Control conditions

  • When a malfunction in the crankshaft position sensor or exhaust camshaft position sensor is detected

Dechoke control

    Purpose

  • To improve engine startability when spark plugs are flooded (scavenging)

    Control conditions

  • When cranking close to fully-open throttle valve


Boost Circuit

Output Circuit


Fuel injector status

PCM operation

Opening starts

  1. Provides 40V, boosted by the boost circuit, to the opening transistor (40 V output).

  2. Voltage is provided to the fuel injector, the ground transistor is turned on and grounded, and the fuel injector opens.

  3. After the fuel injector is opened, the opening transistor is turned off.

Opening held

  • Controls the on/off of the holding transistor (12 V output) so that the hold current of the fuel injector is constant.

Closing

  • Turns off the holding and ground transistors at the same time the fuel injection signal from the PCM is stopped, and cuts the current.


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