The need for significant reduction of fuel consumption and CO₂
emissions has become the major driver for development of new
vehicle powertrains today. For the medium term, the majority of new
vehicles will retain an internal combustion engine (ICE) in some
form. The ICE may be the sole prime mover, part of a hybrid
powertrain or even a range extender; in every case potential still
exists for improvement in mechanical efficiency of the engine
itself, through reduction of friction and of parasitic losses for
auxiliary components.
A comprehensive approach to mechanical efficiency starts with an
analysis of the main contributions to engine friction, based on a
measurement database of a wide range of production engines. Thus
the areas with the highest potential for improvement are
identified.
For each area, different measures for friction reduction may be
applicable with differing benefits. The proposed measures may be
cost intensive, such as the addition of low friction coatings, or
variable-capacity pumps, whereas others such as the optimization of
cylinder bore distortion or coolant pressure drop by design
measures have zero add-on cost. Some are concept-level decisions
only applicable to a new engine design; others can be implemented
without significant investment even for an existing engine
design.
In this paper the major potential improvements to mechanical
efficiency of the internal combustion engine are identified for
each engine system. The improvements are ranked in terms of
friction benefit and impact on product cost.
