vex ~
again, in as much as i understand what you have said in your post (i'll still need some time to understand the Otto cycle graph you posted
, but i haven't read the accompanying link yet) i can't disagree with what you're saying. in fact, i agree wholeheartedly. i guess the problem with me is that i agree with all the points of view because the lines of comparison are blurred.
however, it still comes down to our individual perceptions on where the lines of comparison (rotors vs. pistons) are to be drawn. i suppose the best thing may be making no comparisons at all, but it's probably not going to happen.
i've never thought of the housing surface as one cylinder (sleeve), so that is yet another point of view to consider - and in that context it is quite consistent with 1308. it's new, at least to me it is. i don't see it as any more (or less) right as any of the other points of view.
that said, it makes sense with the TDC-to-BDC definition of displacement. the eccentric shaft only allows one TDC per rotor and that would also be the reason why you said the rotor should be treated like a piston. i get that. again, it's not that i reject any of the other assertions, i just find myself gravitating to the 3.9 more than the others.
for what it's worth, regardless of what i posted before (or in the future) about the 3.9 displacement theory, i do still consider our beloved 13B to officially be a 1.3L powderkeg of fury - just not in an absolute sense. as far as what to consider any of the rotary engines, i believe Mazda's final and absolute determination trumps mine any day and i'm good with that.