Piper Power Settings?

So, I'm going through the performance charts for my new ride (in
case anyone missed my long postings), and there's a graph that
lists fuel flow for a given power setting (eg. 9.16 GPH @ 65%).
Another charts lists MP at altitude for each power setting.

The weird thing is the MP drops with altitude. ISTM, at constant
power, MP should increase to compensate for reduced air density.
I.e. at a given fuel flow, which translate to a given power, you
need a bigger volume of air to maintain the proper mixture.

We're talking small changes in MP, few 1/10th of inches per 1000',
but they're definitely decreasing with altitude.

Am I wrong or are the tables bogus?


Morris (so why didn't Jim Fisher comment on my transition to low wings?)