Audi Secondary Air Injection Maintenance. This manual air injection maitenance apply for Audi vehicle model as follow : Audi A6 Sedan 1998-2004, Audi A6 Avant 1999-2004, Audi allroad quattro 2001-2004, Audi S6 Avant 2002-2004, Audi RS6 2003-2004 – 4.2 Liter V8 5V Engine Mechanical, Engine Code(s): BAS. The secondary air system is designed to enable catalytic converter to heat up and reach its operating temperature more quickly after a cold start. Due to extra mixture enrichment during cold-start phase, an increased amount of unburnt hydrocarbons is carried in exhaust gas. The secondary air system improves the after burning (oxidation) process in the catalytic converter, and in this way reduces toxic emissions. Heat generated by oxidation accelerates “light off” of catalytic converter and significantly improves exhaust gas quality during warm-up.

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