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Assessment of Stoichiometric Gdi Engine Technology
Published September 04, 1997 by AVL List GmbH in Australia
Event: Engine and Environment~Fuel Economy Versus Emissions Gasoline and Diesel Direct Injection~The Best Way Towards the Future?
The recent availability of flexible and reliable common-rail fuel injection systems is giving a push to the development of a new generation of GDI engines.
The GDI stoichiometric engine concept permits to improve fuel economy up to 10% without major modifications to the combustion system and cylinder head architecture. This is possible thanks to the combined effect of increased compression ratio, improved air/fuel metering control during transients, improved EGR tolerance and the possibility to downsize the engine, allowed by the increased power output (up to 10%).
Thanks to the demonstrated capacity for reducing both steady state and transient emissions of HC and NOx by controlling properly the injection timing, an excellent potential is given for satisfying all future European emission standards with well- assessed aftertreatment technologies.
The development and application of the GDI ultra-lean concept remains of course very attractive for its potential for fuel consumption reduction ranging from 15-20%. The fuel injection and combustion system will, however, have to meet much more stringent requirements concerning fuel atomization, consistency, production line tolerances and long-term operation stability, in order to guarantee a proper and stable control of charge stratification.
The aftertreatment of NOx as well as HC for meeting the Euro 4 limits is still a difficult issue because of the catalyst requirements (durable 90% DeNOx efficiency and low sulfur fuel availability) and the low exhaust gas temperatures.
Therefore, the λ=1 GDI engine has an excellent potential for meeting tomorrow's powering needs of passenger cars.