BMW N62B44, Руководство пользователя

Страница: 16 / 55

Silencers
• A 1.8 liter capacity front silencer has been fitted for each cylinder bank.
• A single 5.8 liter center silencer is fitted downstream of the two front silencers.
• The resonator type rear silencers have capacities of 12.6 and 16.6 liters.
Exhaust Gas Flap
The 12.6 liter rear silencer is fitted with an exhaust gas flap to keep noise to a minimum at
engine idle speed and low rpm. The exhaust gas flap is opened allowing additional flow
when:
• The a transmission gear is engaged a an nd d
• The engine speed is above 1,500 rpm
A vacuum-controlled diaphragm (actuator mounted on the silencer) opens and closes the
exhaust gas flap. The exhaust gas flap is closed with vacuum, and is sprung open by the
actuator (when vacuum is not present). The procedure is carried out using a solenoid valve
which is electrically controlled by the ECM.
Secondary Air System
Blowing additional air (secondary air) into the cylinder head exhaust ducts during the warm-
up phase results in a thermal secondary combustion which results in a reduction of the
non-combusted hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas. The
energy generated during this process heats up the catalytic converter faster during the
warm-up phase, and increases it’s conversion rate.
14
N62 Engine
43-02-05
Secondary Air System
1. Air Intake Duct
2. Air Cleaner housing with Intake Air Silencer
3. Intake Pipe with HFM (Hot-Film Air-Mass
Sensor)
4. Non-return Valves
5. Secondary Air Pump