An Assessment and Comparison of De-Throttling Approaches and Technologies for Maximum Reductions in Fuel Consumption in a modern GDI engine

Paper #:
  • 2017-01-2224

  • 2017-10-08
REVISED ABASTRACT 4/7/2017 The challenges of maintaining continuous improvements in air quality, manage the earth’s energy resources, and to control atmospheric concentrations of greenhouse gasses, whilst supplying ever increasing global sales volumes mean that ever more detailed understanding and optimisation of powertrain systems is required. Downsizing, electrification and traffic flow management all have very important parts to play in achieving these goals, but can still only modify the outputs of the basic propulsion units, and methods to improve the efficiency, cleanliness and flexibility of powertrains remains a vital development requirement. The paper explores the fuel consumption benefits available from de-throttling technologies that can help to bring gasoline engine efficiency on a par with that of diesel engines. The paper shows the relative efficiency improvements offered by a fully-variable intake valve lift system in conjunction with wide-range cam phasers, which also incorporate the facility to provide zero valve lift to enable cylinder deactivation. Testbed results recorded with a prototype concept engine show the degree to which early Intake valve closing, internal EGR and cylinder deactivation can work together, and the limitations of this synergy at different operating conditions. In conclusion, the paper demonstrates the potential of a production-feasible 2.0 litre Central GDI engine to deliver in excess of 100kW per litre, and yet to achieve less than 300g/kW.h BSFC at 2000/2.0bar BMEP – a value which is competitive with diesel engine efficiencies, whilst benefitting from cleaner combustion, and more robust aftertreatment processes.
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