Mazda X-5. Manual - part 25

EMISSION SYSTEM 

01–16–3

01–16

Exhaust System

Fuel Tank Side

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EXHAUST PURIFICATION SYSTEM OUTLINE [LF]

E5U011600010N01

Feature

• The EGI system (fuel injection control, ignition control) burns fuel supplied to the engine at the stoichiometrical 

air/fuel ratio for improved purification efficiency of the catalytic converter system.

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WU-TWC

TWC

E5U116ZS5008

FUEL-FILLER CAP

AIR FILTER

EVAP SYSTEM LEAK 
DETECTION PUMP

QUICK RELEASE 
CONNECTOR (TYPE C)

CHARCOAL CANISTER

ROLLOVER VALVE

FUEL SHUT-OFF VALVE

EVAPORATIVE CHAMBER

E5U116ZS5030

EMISSION SYSTEM 

01–16–4

EGR SYSTEM OUTLINE [LF]

E5U011600020N01

Features

• An EGR valve with a stepping motor has been adopted for optimum control according to engine operation 

conditions.

• For control of EGR system, refer to CONTROL SYSTEM, EGR CONTROL. (See 01–40–30 EGR CONTROL 

OUTLINE [LF], 01–40–30 EGR CONTROL BLOCK DIAGRAM [LF], 01–40–30 EGR CONTROL OPERATION 
[LF].)

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EGR SYSTEM STRUCTURE [LF]

E5U011600020N02

• Consists of an EGR valve and EGR pipe to conduct exhaust gas to the intake air system.

System diagram

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EGR SYSTEM OPERATION [LF]

E5U011600020N03

• The high occurrence of NO

X

 at high temperatures has been reduced by recirculating exhaust gas to the 

combustion chamber in order to lower the combustion temperature.

• The exhaust gas flows along the EGR passage in the cylinder head and into the EGR valve. Exhaust gas that 

has flowed past the EGR valve flows through the EGR pipe, and is conducted to the dynamic chamber.

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EGR VALVE FUNCTION [LF]

E5U011620300N01

• Adjusts the amount of exhaust gas to be recirculated from the exhaust system to the combustion chamber 

based on the EGR control signal from the PCM.

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EGR VALVE CONSTRUCTION/OPERATION [LF]

E5U011620300N02

• Consists of a rotor, coils, and a spring.

• Operates based on the signal from the PCM to 

drive the EGR valve stepping motor.

• The PCM determines the optimum EGR valve 

opening angle based on the engine speed and 
intake air amount when the engine is completely 
warmed up and drives the EGR valve.

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EGR VALVE

: TO PCM

EGR PIPE

E5U116ZS5002

A

B

C

E

A

B

F

D

C

D

E

F

EGR VALVE

PCM

MAIN 
RELAY

C3U0116S031

EMISSION SYSTEM 

01–16–5

01–16

CATALYTIC CONVERTER SYSTEM OUTLINE [LF]

E5U011600050N01

Feature

• Purifies contaminants in the exhaust gas by utilizing a chemical reaction in a three way catalytic converter.

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CATALYTIC CONVERTER SYSTEM STRUCTURE [LF]

E5U011600050N02

• Consists of a three way catalytic converter and insulator.

• The WU-TWC utilizing a platinum-rhodium-palladium system has been adopted.

• The TWC utilizing a platinum-rhodium system has been adopted.

System diagram

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CATALYTIC CONVERTER SYSTEM OPERATION [LF]

E5U011600050N03

• Contaminants in the exhaust gas (HC, CO, NO

X

) are purified by oxidization and deoxidization while passing 

through the catalytic converter.

— Oxidization process

• Noxious HC (hydrocarbon) and CO (carbon monoxide) are bonded to oxygen which is converted to 

non-noxious carbon dioxide and water.
O

2

 + HC + CO 

→ CO

2

 + H

2

O

— Deoxidization process

• Noxious NO

X

 (nitrogen oxide) is converted to non-noxious nitrogen and oxygen. A part of the oxygen 

generated at this time is used in the oxidization process.
NO

X

 

→ N

2

 + O

2

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WU-TWC

TWC

E5U116ZS5852

EMISSION SYSTEM 

01–16–6

POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM OUTLINE [LF]

E5U011600040N01

Feature

• A closed type PCV system has been adopted.

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POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM STRUCTURE [LF]

E5U011600040N02

• Consists of a PCV valve and ventilation hose.

• The PCV valve is installed on the oil separator.

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POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM OPERATION [LF]

E5U011600040N03

• Blowby gas (unburnt gas), including CO and HC exhausted from the crankcase, is forced into the intake air 

system and burned in the combustion chamber to prevent its atmospheric release.

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POSITIVE CRANKCASE VENTILATION (PCV) VALVE FUNCTION [LF]

E5U011613890N01

• Adjusts the amount of blowby gas conducted to the intake air system according to the intake manifold vacuum.

• Regulates the air (including blowby gas) passing from the cylinder head cover to the intake manifold during low 

load (when vacuum in the intake manifold is high) to ensure an optimum air/fuel ratio.

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POSITIVE CRANKCASE VENTILATION (PCV) VALVE CONSTRUCTION/OPERATION [LF]

E5U011613890N02

• Consists of a spring and valves.

• The PCV valve ensures the passage of blowby 

gas by opening the valve according to the intake 
manifold vacuum, and adjusts the amount of gas 
by spring force.

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OIL SEPARATOR

PCV VALVE

VENTILATION HOSE

E5U116ZS5853

PCV VALVE

TO DYNAMIC 
CHAMBER

SPRING

INTERNAL VALVE

FROM OIL SEPARATOR

E5U116ZW5043