Mazda X-5. Manual — part 21

INTAKE-AIR SYSTEM

01–13–5

01–13

INTAKE MANIFOLD/DYNAMIC CHAMBER CONSTRUCTION [LF]

E5U011313100N01

• The intake manifold composed of the variable intake air shutter valve actuator.

End Of Sie

VARIABLE INTAKE AIR SYSTEM FUNCTION [LF]

E5U011300020N01

• The variable intake air system maintains high torque from the low to high engine speed ranges.

• If any of the following conditions are met, the effective intake manifold length is changed to enhance the inertia

charging effect. As a result, higher torque is obtained in all ranges.

— Engine speed is approx. 4,750 rpm or more.

— Engine speed is approx. 3,150 rpm or less and the throttle opening angle is the specified value or more.

(heavy load condition)

• For the variable intake air control, refer to CONTROL SYSTEM, Variable Intake Air Control (See 01–40–15

VARIABLE INTAKE AIR CONTROL OUTLINE [LF].)

Inertia charging effect

— Airflow in the intake air pipe pulsates according to the opening and closing of the intake valve. When the

intake valve closes, intake air is compressed near the intake valve due to inertia force. The resulting
pressure wave is reflected to the throttle valve side by the intake valve and the wave is then reflected back
to the intake valve side when it reaches the dynamic chamber. The effective intake manifold length is
controlled so that the pressure wave returns to the intake valve at the intake stroke. Due to this, air intake
volume increases, resulting in higher torque.

Effective intake manifold length

— The effective intake manifold length is the length from the intake valve to the dynamic chamber.

— The effective intake manifold length changes according to the positioning of the reflected pressure wave

transmitted through the intake air pipe by the opening and closing of the variable intake air shutter valve in
the dynamic chamber.

End Of Sie

VARIABLE INTAKE AIR
SHUTTER VALVE
ACTUATOR

INTAKE MANIFOLD

DYNAMIC CHAMBER

E5U113ZS5015

CLOSING AREA

OPENING
AREA*1

HIGH

HIGH

LOW

LOW

ENGINE TORQUE

ENGINE SPEED

APPROX. 4,750 RPM

OPENING AREA

: VARIABLE INTAKE AIR
SHUTTER VALVE OPEN

: VARIABLE INTAKE AIR
SHUTTER VALVE CLOSED

*1: THROTTLE OPENING ANGLE IS THE SPECIFIED VALUE OR MORE

E5U113ZS5002

INTAKE-AIR SYSTEM

01–13–6

VARIABLE INTAKE AIR SYSTEM STRUCTURE [LF]

E5U011300020N03

• Mainly consists of the variable intake air solenoid valve, variable intake air shutter valve, variable intake air

shutter valve actuator and vacuum chamber.

End Of Sie

VARIABLE INTAKE AIR SYSTEM OPERATION [LF]

E5U011300020N04

Operation Conditions

• If any of the following conditions are met:

— Engine speed is approx. 4,750 rpm or more.

— Engine speed is approx. 3,150 rpm or less and the throttle opening angle is the specified value or more.

(heavy load condition)

Except for Operation Conditions. (Variable Intake Air Shutter Valve Is Closed)

• Intake manifold vacuum is applied to the variable intake air shutter valve actuator by the operation of the

variable intake air solenoid valve, closing the variable intake air shutter valve.

• Under this condition, the effective intake manifold

length is from the intake valve to the dynamic
chamber (A—C). An inertia charging effect is
obtained due to this elongated intake manifold
length, air intake volume increases, and higher
torque is obtained at low to medium engine
speeds.

VARIABLE INTAKE AIR
SOLENOID VALVE

: TO PCM

CHECK VALVE

VACUUM CHAMBER

DYNAMIC
CHAMBER

VARIABLE
INTAKE AIR
SHUTTER VALVE

VARIABLE INTAKE AIR
SHUTTER VALVE ACTUATOR

E5U113ZS5003

VARIABLE
INTAKE AIR
SHUTTER
VALVE
CLOSED

DYNAMIC
CHAMBER

C

A

E5U113ZS5004

INTAKE-AIR SYSTEM

01–13–7

01–13

When Operation Conditions Are Met. (Variable Intake Air Shutter Valve Is Open)

• The variable intake air shutter valve is open.

• Under this condition, the effective intake manifold

length is from the intake valve to the dynamic
chamber (B—C). The intake air inertia effect is
obtained at high engine speeds due to this
shortened intake air pipe, increasing intake
airflow amount in the cylinder, and higher torque
at high engine speeds is obtained.

End Of Sie

VARIABLE INTAKE AIR SOLENOID VALVE FUNCTION [LF]

E5U011318742N01

• Switches the intake manifold vacuum passage between the dynamic chamber and the variable intake air

shutter valve actuator.

End Of Sie

VARIABLE INTAKE AIR SOLENOID VALVE CONSTRUCTION/OPERATION [LF]

E5U011318742N02

Construction

• Mainly composed of the solenoid coil, spring, and plunger.

Operation
Energized

• The solenoid coil magnetizes, pulling the plunger. The passage between A and B ports opens due to the

plunger being pulled, and intake manifold vacuum is applied to the variable intake air shutter valve actuator.

Not energized

• The intake manifold vacuum passage is blocked, and the passage between ports B and C opens,

depressurizing the variable intake air shutter valve actuator.

End Of Sie

VARIABLE
INTAKE AIR
SHUTTER
VALVE OPEN

DYNAMIC
CHAMBER

C

B

E5U113ZS5005

SOLENOID COIL

PLUNGER

SPRING

ENERGIZED

PORT A

PORT B

NOT ENERGIZED

PORT B

PORT C

E5U113ZS5006

INTAKE-AIR SYSTEM

01–13–8

VARIABLE INTAKE AIR SHUTTER VALVE ACTUATOR FUNCTION [LF]

E5U011320132N01

• Opens and closes the variable intake air shutter valve.

End Of Sie

VARIABLE INTAKE AIR SHUTTER VALVE ACTUATOR CONSTRUCTION/OPERATION [LF]

E5U011320132N02

Construction

• Mainly consists of the body, rod, diaphragm chamber and spring.

Operation

• Normally, the spring force presses against the rod, keeping the variable intake air shutter valve open. When

vacuum is applied to the diaphragm chamber from the dynamic chamber, the rod is pulled, closing the variable
intake air shutter valve.

End Of Sie

VARIABLE INTAKE AIR

SHUTTER VALVE OPEN

ROD

VARIABLE INTAKE AIR

SHUTTER VALVE CLOSED

VARIABLE INTAKE AIR

SHUTTER VALVE

SPRING

DIAPHRAGM

CHAMBER

INTAKE

MANIFOLD

VACUUM

E5U113ZS5007