Good points on the concept, but the displacement increase from a 12A (70 cubic inches) to a 13B (90 ci) is due to a wider rotor and rotor housing. Unless you are able to roduce those you are out of luck...and nobody would ever try, because detection is is easy as measuring the outside of the engine with a tape measure!
As MM points out, porting is the ticket. The ports, at the point where they enter the rotor chamber, can be "eased"...very little...and the gains can be significant. I know that the 12As are "checked" with a "go/no go" guage called a lolipop at certain SE races, such as the ARRCs, and that a probe with a finger is done as well, but my research indicates that significant gains are possible even with those checks being performed.
I also understand that the 13B (ITS) motors can not be checked with the guage, as none exist.
Recent "rumours" are about that suggest that "new" hp has been found in ITS using a tricky method of increasing breathing. It's not legal of course, but tough to prove, even if you know what you are looking for. Of course, that's all rumours and innuendo, nothing has been proven much less protested. So, I don't put much stock in those....not yet at least, LOL.
So, to answer your question, yes, there are gians possible, and a teardown is needed to find them, but it is very invasive...much more than checking a cam for instance, on most piston engines.
than a search site. What you get here are different perspectives.
