Exhaust System: Description and Operation
Exhaust System / Emission Control
The exhaust system not only ensures that pollutants are cleaned from combustion exhaust gases, it also has a significant effect on the acoustics of the vehicle. The main function of the exhaust system is after-treatment of the exhaust gas.
Cayenne S exhaust system
Twin-branch exhaust system with branch coupling connection
1 Exhaust manifold, bank 1/2
2 Wideband oxygen sensor LSU 4.9 ahead of catalytic converter, bank
3 Primary catalytic converter (ceramic substrate), bank 1/2
4 Step oxygen sensor LSF 4.2 behind catalytic converter, bank 1/2
5 2 main catalytic converters (metal substrate), bank 1/2
Cayenne S emission control
USA: ULEV
EU: EURO 5 (with secondary-air injection)
As a result of combustion of the fuel-air mixture, small quantities of pollutants (nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO) and soot particles) are produced in addition to CO2 and water vapor.
In order to ensure compliance with all the globally valid emission regulations, all Cayenne models have an exhaust system that is specially adapted to the respective engine unit. All exhaust systems are made of long-life stainless steels.
To keep emissions low in the cold start phase in particular, it is important that the catalytic converter reaches its optimal operating temperature quickly. For this reason, the exhaust manifolds of all V8 Cayenne models are designed very short so that the high exhaust temperature can be used to heat the catalytic converters. This allows the highly-efficient primary and main catalytic converters to heat up quickly and guarantee effective emission control.
The cylinder bank-specific LSU oxygen sensors ahead of the catalytic converter and LSF oxygen sensors behind the catalytic converter signal the exhaust gas composition to the DME control unit. The DME control unit can then use this information for targeted intervention in bank-specific mixture control. This ensures that the strictest emission standards are met or even bettered.