# 56 / May 2017 / Focus: Exhaust gas - a closer look

City driving is way different in laboratory dynamometers and in reality: Drivers start their cars from the cold and really floor the throttle to overtake. At traffic lights almost everyone tries to make up for lost time. Others look to flaunt the expensive horsepower they’ve splashed out on as they roar past sidewalk bars and cafes.

This driving behavior is stretching the exhaust gas cleaning in diesel and gasoline cars to its limits. Until now, the law has turned a blind eye precisely here and relied on unrealistic tests on test rigs to set limits and classify cars. As a result, some pollutants slip through the net (virtually) unbridled while others are only produced in the hot catalytic converter from the chemically reactive ingredients that the engine provides. But what really comes out the rear end? Empa has been on the case (see pages 08 – 20).