I’m flying an ES-P, so my speed is much slower, but I can easily cruise at FL220 with a MAP of 24” and still maintain 5.5 psi cabin differential.

LOP, I’m doing the following:

65% power, 25” MAP, 2400 RPM, 15.1 GPH, 202 kts TAS

70% power, 28” MAP, 2400 RPM, 17.0 GPH, 212 kts TAS

So 12% more fuel is getting me only 5% more airspeed.  I see a similar ratio when going from 70% to 75% power.

Lancair IVP Pilots:

We have been recently reviewing LOP cruise numbers for the benefit of sharing with outher LIVP drivers.  Here's some numbers that have come out of the discussion:

          LOP Cruise: 28" MAP 2300 RPM 14.0 GPH

          LOP Cruise: 31" MAP 2400 RPM 15.1 GPH

          LOP Cruise: 34" MAP 2500 RPM 18.0 GPH

One individual offered: "Climb - full power - full rich" (I assume this is 38.5" MAP, 2700 RPM, 43 GPH ROP, 350 HP), then "Level off at FL22, FL23 - full power - full rich" then "After this LOP at FL22, FL23 at 28 inHG, 16.1 gph" which sounded interesting with outstanding speed numbers.

I have some questions for the group of more (than me) informed pilots.

1.  Pressurization: When climbing at full power (38.5" MAP) or even 36" or 34" or (the original recommended 31" MAP), upon leveling off at the flight levels, if you reduce your MAP, you will lower your cabin pressurization, perhaps somewhat significantly.  If I were at 38.5" MAP (or even 34" MAP) during full power climb to the flight levels, I would have 5.0+ psi cabin differential.  If I quickly reduced MAP to 31", and particularly to 28" MAP, the cabin altitude would quickly climb to >14,000' and the Duke's regulator would take several minutes to equilibrate.  And even then, it might not be able to restore 5.0 psi differential (at 28" MAP).  So, all this talk of lower MAP