One Dot.
I don't think Power recovery turbines can be the answer. I understand they were only fitted to the Wright 3350s. (Plus a couple of British engines). Certainly SOME large Pratt and Whitney engines had superchargers AND turbochargers (the 4360 ?) but I think the 2000 and 2800 only had superchargers ?
If I've got that wrong I'm sure someone will correct me.
So we're no nearer an explanation as why at constant rpm SOME supercharged engines will maintain manifold pressure and others won't. Come on 411........... give us the answer