I'm gonna put this one up just because I like the numbers. Groundspeed is nice (221 knots) but check the TAS vs fuel flow, 192 at 9.8. Settings are simple; WOT, adjust RPM for an indicated 65%, and lean to peak at 23 degrees BTDC.
Pressure recovery for the combustion air intake is pretty good. 21.4 Hg is measured at the usual #3 intake port. Static pressure for this altitude and temperature is 20.98, so delivered MP increase due to ram is 0.4" Hg after all intake tract losses, here including a filter which hasn't been cleaned since last January.
How much intake tract loss? Total pressure at this PA, temperature, and velocity is 22.3 Hg, but you can't recover all of it for several reasons. In the case of an engine intake (and just like cooling air), the noteworthy factor is that the "pitot" is not a closed end system. At 2500 RPM, if we assume engine VE is 90%, the calculated total pressure inside the airbox, before the filter, would be 21.9 rather than 22.3, so the overall intake tract loss for the 390, with filter and FM200, appears to be about 0.5" Hg.
Please excuse the crappy photo. The sun was at an entirely wrong angle.
Pressure recovery for the combustion air intake is pretty good. 21.4 Hg is measured at the usual #3 intake port. Static pressure for this altitude and temperature is 20.98, so delivered MP increase due to ram is 0.4" Hg after all intake tract losses, here including a filter which hasn't been cleaned since last January.
How much intake tract loss? Total pressure at this PA, temperature, and velocity is 22.3 Hg, but you can't recover all of it for several reasons. In the case of an engine intake (and just like cooling air), the noteworthy factor is that the "pitot" is not a closed end system. At 2500 RPM, if we assume engine VE is 90%, the calculated total pressure inside the airbox, before the filter, would be 21.9 rather than 22.3, so the overall intake tract loss for the 390, with filter and FM200, appears to be about 0.5" Hg.
Please excuse the crappy photo. The sun was at an entirely wrong angle.