Mazda RX-8 2004 - Catalytic Converter System; Catalytic Converter System Operation; Emission System Structural; Secondary Air Injection (Air) System Construction;Operation

EMISSION SYSTEM
01–16–3
01–16
CATALYTIC CONVERTER SYSTEM STRUCTURE
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• The catalytic converter consists of a three-way catalyst and insulator.
• A 3.01 L {3.18 US qt, 2.65 lmp qt} capacity catalytic converter with a three-way platinum-palladium-rhodium
based catalyst has been adopted.
System Diagram
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CATALYTIC CONVERTER SYSTEM OPERATION
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• Toxic substances (HC, CO, NO
X
) in exhaust gas are purified by oxidization and reduction while passing
through the catalytic converter.
— Oxidation
• Combines toxic HC and CO with oxygen to produce non-toxic carbon dioxide and water.
O
2
+ HC + CO → CO
2
+ H
2
O
— Reduction
• Converts toxic NO
X
(nitrogen oxides) into non-toxic nitrogen and oxygen. Part of the oxygen produced
in this process is used for oxidation.
NO
X
→ N
2
+ O
2
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SECONDARY AIR INJECTION (AIR) SYSTEM OUTLINE
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Features
• Supplies secondary air discharged by the AIR pump to the exhaust ports.
• Rapid activation of the catalytic converter system is achieved by sending secondary air to the exhaust ports
and causing it to react with unburnt gas to raise exhaust gas temperature.
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SECONDARY AIR INJECTION (AIR) SYSTEM CONSTRUCTION/OPERATION
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• The AIR system is controlled by the PCM.
• If the engine is started when the conditions for actuating the AIR system are satisfied, the AIR pump operates,
pumping air to the AIR control valve. At this point, the PCM turns on the AIR solenoid valve, causing negative
pressure in the vacuum chamber to open the AIR control valve. Due to this, the air pumped by the AIR pump is
passed through the secondary air ports and introduced into the exhaust ports in the side housing as secondary
air. The secondary air reacts with unburnt gas discharged from the rotor housing thereby raising exhaust gas
temperature and enhancing catalyst activation. When the AIR pump stops, the AIR solenoid valve turns off,
closing the AIR control valve and preventing the reverse flow of exhaust gas from the exhaust ports to the AIR
pump.
• The AIR pump only operates for a short period after a cold start. (Except extreme cold engine starts)
PRESILENCER
EXHAUST MANIFOLD
TWC
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