Charge Cycle as Key to Emissions

Auszug

The charge cycle is becoming increasingly significant with the forthcoming, more dynamic fuel consumption test cycles, such as the Worldwide Harmonized Light Vehicles Test Procedures (WLTP) and the Real Driving Emissions (RDE) specification for measuring on-road emissions. The key to achieving reduced engine-out emissions in transient operation is using a purpose-built air flow. The aims targeted with the charge cycle of a combustion engine have thus changed significantly. The classical focus, particularly for naturally aspirated engines, was improving cylinder charging through swift gas exchange. The biggest change came with the post-70s introduction of multi-valve technology, which paved the way to achieve higher specific performance and torque. Meanwhile, camshaft phasing systems allow valve timings to be controlled on both inlet and outlet sides. Whereas early systems only switched between two valve timing settings for the inlet camshaft, infinitely variable systems soon followed. …