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Exhaust system
When the car is accelerated at full throttle, the typical sound of
the five-cylinder engine is delightfully resonant in the intake and
exhaust system. And yet the sound is unobtrusive when driving at a
constant speed and under moderate acceleration.
To ensure compliance with the EU-5 exhaust emission standard, it
was necessary to position the pre-catalyst as close as possible to
the turbine outlet. The catalytic converter is made of a ceramic
material. The continuous-duty oxygen sensor, which is integrated
directly in the exhaust turbocharger module, is also positioned at
the turbine outlet. The post-cat oxygen sensor is located directly
downstream of the pre-catalyst and has a non-linear characteristic.
The two underbody catalytic converters are positioned further
down the exhaust system, which has a twin-flow configuration
after the pre-catalyst. Both catalytic converters are of metal con-
struction.
A further focal point in the development of the exhaust system
was minimising exhaust gas backpressure. Hence, the exhaust
pipes are very large and, in part, have a twin-flow configuration.
A sport exhaust system with black tailpipe trims is available as an
option, in addition to the basic exhaust system. It has an even
more distinctive soundscape.
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Exhaust flap
The exhaust gases are admitted into the large rear silencer behind
the two centre silencers. The rear silencer, in turn, has twin tail-
pipes.
The left tailpipe is fitted with an exhaust flap. When this flap
opens, the sound becomes even more sporty. The exhaust flap is
opened and closed by a vacuum cell. For this purpose, the exhaust
flap 1 valve 1 N321 is activated by the engine control unit.
If the Sport button is pressed at idle and when the vehicle is at a
standstill, the exhaust flap opens, thus allowing the system to be
checked quickly and easily. The opening and closing of the exhaust
flap are otherwise computed by a map in the engine control unit.
If the exhaust flap 1 valve 1 N321 fails or if a leakage occurs in the
hose system, the exhaust flap stays continuously open.
Pre-catalyst Isolating elements
Underbody catalytic converters Centre silencer Tailpipe trims
Rear silencer
Vacuum cell
