A simulation study was conducted to investigate the benefits of two-step and three-step EIVC (early intake valve closing) strategies on spark-ignited engines. By combining these strategies with cam-phasing, significantly improved fuel economy, NOx emissions, and low-speed BMEP was demonstrated. These strategies reduce pumping losses and provide increased internal dilution (subject to combustion limits) for improved indicated thermal efficiency and reduced NOx emissions. The application dependent results lead to following conclusions: Longer duration low-lift cam profiles of 210 to 226 CAD are preferred for high fuel economy, low NOx emissions, and increased low-speed BMEP. However, more advanced intake valve timing is needed compared to shorter duration profiles. Two-step EIVC with DICP (dual independent cam phasing) improves fuel economy about 8% relative to a fixed-cam baseline without EGR, or about 6% relative to the same engine with DICP alone. This system provides most of the fuel economy benefit and NOx reduction of a hypothetical eight-step EIVC system. Three-step EIVC with DICP improves fuel economy about 9% relative to a fixed-cam baseline without EGR, or about 7% relative to the same engine with DICP alone. This system provides still comparable fuel economy and NOx emissions to that of a hypothetical eight-step EIVC system. Low-speed engine volumetric efficiency was improved about 12% for low-lift cam duration of 234 CAD and about 6% for duration of 226 CAD. Exhaust cam phasing improves fuel economy about 1% and reduces NOx emissions relative to two-step EIVC with intake cam phasing alone. Engine operation at reduced valve lift reduces in-cylinder tumble and may degrade combustion under dilution combustion conditions. Generally, both two-step and three-step EIVC with cam-phasing hold good promise for high volume production applications on spark-ignited engines.


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    Title :

    Two-step variable valve actuation for fuel economy, emissions, and performance


    Additional title:

    Zweistufig variable Ventilsteuerung zur Kraftstoffeinsparung, Emissionsminderung und Leistungssteigerung


    Contributors:
    Sellnau, M. (author) / Rask, E. (author)


    Publication date :

    2003


    Size :

    17 Seiten, 32 Bilder, 3 Tabellen, 59 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




    Two-Step Variable Valve Actuation for Fuel Economy, Emissions, and Performance

    Rask, Eric / Sellnau, Mark | SAE Technical Papers | 2003


    Two-step variable valve actuation for fuel economy, emissions, and performance

    Sellnau,M. / Rask,E. / Delphi Research Labs,US | Automotive engineering | 2003



    Variable valve actuation.

    Demmelbauer-Ebner,W. / Dachs,A. / Lenz,H.P. et al. | Automotive engineering | 1991