But the thing is, RB does not stand for "race bred", or "racing breed", or whatever else ignorant rice sites tell you. =\The first RB's were relatively weak so I doubt the naming was premeditated...
(Watch him bring up some reputable site proving me wrong...

)
But I'm pretty sure they're just letters.
Note: It's been my experience that engine codes starting with "V" are always in a V configuration. i.e.- VG, VH, VK, VQ...