Exhaust Manifold With Catalytic Converter; Silencer - BMW N62 Series Service Training

New Generation N62 Engine

- Exhaust manifold with catalytic converter

A four-into-two-into-one manifold has been fitted for each
cylinder bank. The manifold and the catalytic converter housing
together form one component.
A ceramic-bed pre-catalytic converter and a ceramic-bed main
catalytic converter are arranged one behind the other in the
catalytic converter housing.
The supports for the broadband planar oxygen sensors
(Bosch LSU 4.2) and the secondary oxygen sensors are located
in front of and behind the catalytic converter in the headpipe or
catalytic converter outlet funnel.

- Silencer

An absorption-type, 1.8 l capacity front silencer has been fitted
for each cylinder bank.
An absorption-type, 5.8 l centre silencer is fitted downstream of
the two front silencers.
The rear silencers are of the resonator type, and have capacities
of 12.6 and 16.6 litres.
Exhaust gas flap
To keep noise to a minimum at engine idling speed and near
engine idling speeds, the rear silencer is fitted with an exhaust
gas flap. The exhaust gas flap is opened when a gear is
engaged and the engine speed is above 1,500 rpm. This
activates an additional rear silencer capacity of 14 litres.
A vacuum-controlled diaphragm box opens and closes the
exhaust gas flap. The exhaust gas flap is closed using vacuum
pressure, and is opened by ventilating the diaphragm box.
This control procedure is carried out using a solenoid valve
which is electrically actuated from the DME.
© BMW AG, Service Training
Course Contents/Background Material
Chapter 3 P.16