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]

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• 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]

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• 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]

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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

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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]

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• 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

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INTAKE-AIR SYSTEM 

01–13–8

VARIABLE INTAKE AIR SHUTTER VALVE ACTUATOR FUNCTION [LF]

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• Opens and closes the variable intake air shutter valve.

End Of Sie

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

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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