I have heard some quote manifold absolute pressure (MAP) which I would think is good because on a turbocharged engine, it is what matters.  It seems like your numbers are gauge pressure?  But is it gauge above ambient pressure, or just simply a MAP with sea level pressure subtracted out (approximately 30")?  Just wondering...  Seems like your motor is not working very hard - great!

That is flying high!  Do you use oxygen (on you not the motor!)?

On Wed, Aug 6, 2014 at 11:38 AM, Tracy <flyrotary@lancaironline.net> wrote:

Here's some trip data from a flight from Florida to Colorado in the 20B powered RV-8.    It's the first long trip where I was able to fly at or near the altitudes it was optimized for.   It didn't do as well as I had hoped in terms of fuel economy but the numbers were as good or slightly better than the typical Lycoming powered RV numbers I hear.   It is only slightly faster than my Renesis powered RV-4 at cruise conditions and reasonable fuel flow.  But what I like about it is the effortlessness with which it does the job.  There is always a handful of throttle left for reserve in any normal flight situation.

Full throttle is reserved for those few seconds between rudder effectiveness at 30mph and lift off speed at 60.  As soon as the wheels break ground I typically reduce manifold pressure to 24".   Cruise climb is done at between 18 and 19" depending on takeoff weight at around 700 FPM.  Cruise altitude was limited to 15,000 this trip by temperature.  I wasn't thinking and wore only a thin jacket and I don't have cabin heat.   All three legs were flown at 14,500 in a very unusual high pressure system the whole way with almost zero wind.  Here are the raw numbers:

Altitude       14,500
OAT              35 -  43F
TAS              174  -   182 MPH  *
Fuel Flow     8 GPH
Engine RPM  5250 - 5450
Manifold Pressure    14.3"
% Power       30%   (As calculated by EM3)
EGT              1450F
Water temp   145 - 150
Oil Temp       160        (Cowl flap would help temps and airspeed)
Total flight hours on trip  9.2

*  Fuel flow was held constant, TAS varied with fuel batch.  Low number was with Florida gas with about 8% ethanol.   Refueled at Charlie England's place (Thanks for the hospitality and fuel service Charlie!).  Not sure wether it had ethanol or not but TAS was a few MPH better.   After refueling at 47K in Kansas with no ethanol mogas, the TAS reached the highest number.

Tracy

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