Secondary Air Injection

Air injection inlet valve mounts directly to cylinder head, with a passageway machined through the head. This eliminates the external air injection manifold distribution pipes to the exhaust manifolds. To reduce HC and CO emissions while engine is warming up, BMW implemented the use of a Secondary Air Injection System. Immediately following a cold engine start -10°F (-40°C) fresh air/oxygen is injected directly into exhaust manifold.

By injecting oxygen into exhaust manifold, warm up time of catalyst is reduced and oxidation of hydrocarbons is accelerated. Activation period of the air pump can vary depending on engine type and operating conditions. For conditions for secondary air pump activation, see SECONDARY AIR PUMP STATUS/CONDITION  table.