In an age when there is growing tension between customer expectations of high engine performance, low fuel consumption and compliance with the legal requirements on the emission of airborne pollution, the ability of a vehicle to meet the most stringent emission standards is becoming an increasingly important aspect of its market appeal.
The 1.8 l, 5-valve turbo engine which Audi launched in 1994 represented an emissions concept which, thanks to its innovative close-coupled catalytic converter, provided an ideal basis for further development to an engine meeting the US ULEV emission standard, as the current engine does [1].
Its configuration as a ULEV concept necessitated the blanket optimisation of all components which influence the exhaust emissions. The pistons and injectors were improved in order to reduce untreated emissions. The main potential was tapped by incorporating intake camshaft adjustment and a cascade catalytic converter for emissions aftertreatment, together with extensive measures for the engine management system.
The overall concept has enabled Audi to become the first car manufacturer to offer an exhaust-gas turbocharged gasoline engine that meets the US ULEV emission standard.