Exactly, im not saying ringed engines are bad, just that they cant rev as high without suffering ring flutter. If only they could be stable at high speeds, then we wouldnt really have to worry about getting a whole new P/S set, just replace the rings and break THEM in. I would think they would be much cheaper, but until technology advances in that are, the ABC engines, other other types like AAC or whatever, they will still be the way to create a consistant seal (before it wears out)