i was just curious if anyone knows the story behind naming rotary engines, like why is it called the 13b, as with the 20b and 12a. just want to know where the names come from??? im sure there is a reason but i couldnt find it anywhere

 

12A = 1.1L
13B = 1.3L
20b = 2.0L

Makes sense, kinda scary, but thats the japanese for you. kinda like that whole metric system.