“…The practical utility of these models, which require very high computational power, may be questionable in those cases where many repeated computations are involved, as in design applications. Moreover, their quantitative precision, which require an appropriate "balanced precision" in all their sub-models, could even be inadequate for some applications 26 . By a literature analysis on the models devoted to engine control applications, an articulate picture emerges concerning structure, goals and complexity 1,4,5,9 , ranging from input-output black-box models, mostly oriented to control design, to gray-box mean-value models, with a simplified description of the most relevant physical processes 1,2,3 , up to complex 3-D fluid-dynamic models 4,5 .…”