Exhaust System - Audi 4.2-litre V8 FSI Service Training

Exhaust system

Exhaust system
During the development of the exhaust system, special emphasis was placed on optimising flow resistance.
The clamping flange system used in the 2.0-litre FSI engine has proved highly advantageous in this regard.
Audi Q7
Each cylinder bank has its own exhaust pipe.
The air-gap insulated (LSI) exhaust manifolds are
flanged onto the cylinder heads.
They offer the advantage of low heat loss in the
exhaust gas. As a result of this, the primary catalytic
converters are able to heat up quickly.
The primary catalytic converters are ceramic type
catalytic converters. The lambda probes are
connected to them. The lambda probe upstream
of the catalytic converter is a broadband probe.
A nonlinear probe is located downstream of the
catalytic converter. The main catalytic converters
in the underbody area are also ceramic catalytic
converters. The exhaust pipes of the individual
cylinder banks discharge into a front silencer.
The front silencer is an absorption-type silencer.
A crossover function in the silencer ensures higher
engine power output and torque.
The front silencer and the rear silencer are con-
nected by separate pipes.
Again, the rear silencer is a common component
of both exhaust pipes. On the inside of the rear
silencer, however, the left and right exhaust pipes
are clearly separated. Likewise, the rear silencer is
an absorption-type silencer.
Exhaust system in the Q7
Lambda probes
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LSI exhaust manifold
Primary catalytic converter
Decoupling element
Main catalytic converter
Audi RS4
To enhance the sporty character of the RS4 engine,
a fan-type manifold is used in the RS4.
Good separation of the exhaust pulses is ensured
by keeping the individual exhaust pipes apart until
they merge into one. These fan-type manifolds are
also attached by means of the clamping flange
system.
The primary and main catalytic converters are metal
type catalytic converters. Their advantage is that
they have a lower flow resistance than ceramic
catalytic converters. This is good for engine
performance.
The front silencer for each of the exhaust pipes is
housed in a common casing.
However, the exhaust pipes are kept separate.
The front and rear silencers are absorption-type
silencers. They are notable for their low flow
resistance.
Front silencer
Rear silencer
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