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
<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.
--
Paul Lamar ...No rotor no motor.
Great analysis Matt. I think you are right that I was probably running
richer high up in order to get the boost back. Compressor map suggests
my max turbine RPM is around 90K. Should be able to safely close the
wastegate somewhat, but the problem is that I don't trust myself around
a fully enabled turbo. :-) Flying just fine, and don't want to mess
with it.