The gasoline engine and RDE challenges and prospects

Whereas in the past decade, the CO₂ reduction was the major driver for technology development with Gasoline en.gines, especially after the “Dieselgate” an “Extended Emission Compliance” including Real Drive Emissions is taking significant impact on future technology routes. Whereas the RDE legislation initially was targeted primarily towards the Diesel-NOx and the Gasoline-PN emissions, now also the NOx emissions of some Gasoline engine concepts have to be reduced.In a very simplified way, the most significant RDE risk areas of Gasoline engines can be seen in following areas: scavenging at low engine speeds, enrichment and /or exceeding favorable catalyst space velocities at high engine speeds / loads, high load dynamics, in-field stability of PN emissions, insufficient catalyst temperatures and start / restart strategies (esp. Hybrid).As most measures improving the RDE emission show a trade off with CO₂ and / or cost, the future RDE legislation is both a technical but also a commercial challenge. On the other hand, RDE also opens opportunities for the Gasoline engine to increase market shares as with the Diesel engines in some vehicle categories the effort for RDE compliance will be even higher than with Gasoline engines.It is expected that the RDE requirements will enhance the trend from “Extreme Downsizing” towards “Rightsizing”, which was already initiated by modern fuel economy technologies like Miller or Atkinson Cycle. In a next step, also the combination of 48Volt systems with the next generation of Gasoline engines will become a highly competitive technology combination.From a cost / CO₂ reduction perspective, however, both CNG and LPG are most attractive technology approaches to reduce CO₂ and pollutants simultaneously. LPG might be considered as the more simple short-term approach, CNG as the more sustainable long-term solution. With both approaches, the key challenges are not at the pure technical side, but primarily with marketing to gain sufficient customer acceptance.To balance RDE, CO₂ requirements and cost will become one of the most challenging engineering tasks and will require new development and validation approaches. Thus, RDE will not only have a significant impact on powertrain technology, but might also initiate a paradigm shift in powertrain development.