I just finished a most excellent cross country in my [Turbocharged]
   Rotary RV-6 and
   wanted to share the stats and the adventure.  I visited family in
   Boulder, CO, friends in Pensacola, and spent a week in Orlando
   including
   watching the shuttle launch and going to the rotary round up in Bell,
   Fl.  I also delivered a prop to its buyer in Austin TX and traversed the
   country westbound in a single day.

   Best leg (Strong tailwinds fading in the end):  K88-82J,  601 NM and 2.9
   hrs on the hobbs.  23.6 gallons of MOGAS burned that I bought at K88 for
   $2.74/gal.  That works out to 207 Knots [236 MPH] Ground speed at
   8.1 gal/hr.  Yee
   ha! [29 MPG]

   Of course, the winds play the deciding factor.  I had a mix of winds
   over the course of the trip here are the overall stats:
   4224 kn miles traveled
   240 gallons burned
   $3.35 average fuel price (I had to buy 100LL on 2 occasions which
   brought up the average a little)
   $24 worth of 2-stroke oil burned. ($830 total paid for fuel and oil)
   26.0 hrs on the hobbs
   That works out to:
   Average speed= 162 KTS [186 MPH]
   Average Fuel Burn= 9.2 gal/hr [20 MPG]
   Average cost/mile= $0.19

   Those are GPS point to point  numbers and include climb, taxi and
   heading variations.  The other way to look at fuel burn/Cruise speed is
   to use a calibrated ASI and Fuel Flow instrument.  I spent a couple
   hundred miles testing various settings after getting the fuel flow
   computer fully calibrated.  Here are my data points taken in cruise,
   all
   were done > 100 LOP [Lean Of Peak EGT] (more power available with
   richer mixtures
   or closure of the wastegate - not attempted this trip).  Slight
   climbs or
   descents and changes in mixture probably account for the variations.
   (RV is hard to truly keep level especially when looking at other numbers
   and trying to write) (Redline is 7000 RPM)

   150 KTAS @ 13.5k and 8.0 gal/hr
   154 KTAS @ 15.5k and 8.3 gal/hr (5100 RPM)
   160 KTAS @ 11.5k and 9.1 gal/hr
   161 KTAS @ 15.5k and 8.7 gal/hr
   162 KTAS @ 13.5k and 9.2 gal/hr
   165 KTAS @ 13.5k and 10 gal/hr (5600 RPM)
   172 KTAS @ 15.5k and 10.7 gal/hr (5600 RPM)
   179 KTAS @ 15.5k and 12.0 gal/hr (5900 RPM)
   181 KTAS @ 15.5k and 11.8 gal/hr
   183 KTAS @ 13.5k and 12.3 gal/hr
   185 KTAS @ 17.5k and 13.5 gal/hr (6000 RPM)  - WOT
   189 KTAS @ 17.5k and 13.4 gal/hr (6000 RPM)  - WOT
   193 KTAS @ 13.5k and 13.6 gal/hr (6100 RPM)  - WOT

   Clearly not the same fuel economy as most Lycoming installations, but
   not out of the ballpark either.  After considering the lower price of
   MOGAS the hourly cost of flying is [lower?].

   No issues encountered with the engine.  Tracy noted that my [PSRU]
   gear lash
   seemed to be slightly larger than normal, and it increased during the
   trip home.  So next weekend the drive is coming off for inspection and
   likely replacement of the snubbers.


   --
   David Leonard

   Turbo Rotary RV-6 N4VY
   http://N4VY.RotaryRoster.net
   http://RotaryRoster.net <http://RotaryRoster.net
   <http://RotaryRoster.net>>

   Thanks for the report Dave. What were the manifold pressure numbers,
   and coolant temperatures?
   --
   Paul Lamar ...No rotor no motor.


Interesting data.  You obviously need a flight crew (or an autopilot)
for instrumentation flights.  Hah.  :)

I gather that for the fuel EGT/wastgate limits you are using, critical
altitude is 13500'?  Higher than that and the manifold pressure drops
off, and lower than that altitude airframe drag decreases TAS.

Plotting mpg at the various points your list is interesting - fuel
economy at 17500' is worse than at 15500'..

13500'
Kts--Gal/Hr----economy--MPH--MPG
150---8  ----- 18.75 ---174  23
162 --9.2 ---- 17.61 ---188  20
165---10 ----- 16.5-----191  19
183---12.3 --- 14.88----212  17
193---13.6 --- 14.19----223  16

15500'
Kts--Gal/Hr----economy--MPH--MPG
154---8.3 ---- 18.55----178  21
161---8.7----- 18.50----186  21
172---10.7---- 16.07----199  18.6
179---12 ----- 14.91----207  17
181---11.8---- 15.33----210  18

17500'
Kts--Gal/Hr----economy--MPH--MPG
185---13.5---- 13.70----214  16
189---13.4---- 14.10----219  16

I'm guessing that you were running a richer mixture, closer to peak EGT
or even ROP as your boost was dropping?  Any idea what RPM your turbo is
turning at 17500 and whether you can close the wastegate any without
over speeding?


Regards,

Matt-

I added MPH and MPG Matt.