catalytic converter AUDI A4 2000 B5 / 1.G AEB ATW Engines Secondary Air System Workshop Manual

26-29


Secondary air system, checking
(engine code ATW) Following a cold start, the secondary air system
helps to quickly heat the catalytic converter for
quicker operating readiness.
Principle
Due to over-enrichment of the mixture during the
cold start phase, there is an increased amount of
uncombusted carbon monoxide in the exhaust.
Secondary Air Injection (AIR) improves secondary
oxidation in the catalytic converter and therefore
reduces emissions. The heat produced by
secondary oxidation greatly reduces start-up time
for the catalytic converter which significantly
improving exhaust quality during the cold start
phase.
Pa
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