The Cayenne S Diesel features a double-flow exhaust system, with each exhaust tract comprising an oxidation catalyst fitted close to the engine and a diesel particulate filter. In order to minimise thermal losses and ensure that the system is working under ideal conditions, the pipes are completely air-gap insulated. Due to the rapid warm-up of the catalytic converters, the optimum operating temperature is reached earlier so emissions are reduced sooner when starting from cold.

The exhaust-gas recirculation on the Cayenne S Diesel routes part of the exhaust gas back into the combustion process, resulting in lower peak combustion temperature and therefore lower nitrogen oxide emissions.