I flew 3.5 hours from MMV to Logan UT, then 3.0 hours from Logan
UT to
Grant NE yesterday. 165 to 175 knots with a slight 5 to 15 knot
tailwind. There was heavy thunderstorm activity at my destination in
Kansas so I had to stay overnight in Grant.
I used the lean control some, but the ECU tended to "hunt" a
little with
the faked out lean signal so I opted not to use it most of the
time or
used it but only slightly lean. I ran only one fuel pump in
cruise, that
slightly reduces fuel pressure but I don't see much effect on O2
sensor
reading by turning off the second pump.
Still some fog at my destination but I will be leaving soon for the
final 1.0 hour leg.
Perry
Thanks for the report Perry. Good luck with the weather.
--
Paul Lamar ...No rotor no motor.
I arrived at my destination this morning. Analyzed my time and gallon
data and it's not that great. There could be considerable error in the
gallons (estimated by looking at sight gauges) or in the Hobbs meter. I
consistently saw 165 to 175 knots GPS ground speed the whole trip but
the hobbs-based calculations don't agree. I think my no wind speed is
around 160 knots. Some time lost in climb and descent but generally I
did cruise-climbs and descents.
KMMV-KLGU approx. 35 gal., 3.6 hours, 570 nm, WOT at 11,500 feet, 6300
engine RPM, 2900 prop RPM >> 9.7 gph, 16.3 nm/gal, 18.7mpg, 158 knot
average ground speed.
KLGU-KGGF approx. 30 gal., 3.2 hours, 473 nm, WOT at 11,500 feet, 6300
engine RPM, 2900 prop RPM >> 9.4 gph, 15.8 nm/gal, 18.1mpg, 148 knot
average ground speed.
Last year when I did the trip I had no wheel pants, probably ran more
like 6000 engine RPM instead of WOT, had around 150 knot GPS ground speed
during flight (because no wheel pants), and burned 8.8 gph.
Perry
Perry runs the stock Mazda EFI computer so it is more or less
in the high power default mode all the time. In a car the stock
computer monitors the O2 sensor to maintain the mixture at 14.7:1
or AKA stoichiometric during cruise. Unfortunately the O2 sensor
is destroyed by 100 LL fuel. Also above a certain RPM and power
level the stock computer assumes you are accelerating and it reverts
to probably a mixture ratio of around 12.5:1. This is not the best
mixture ratio for cruise. Something on the order of 18:1 or 150
degrees lean of peak EGT gives the best cruise MPG.
Perry has designed an electronic device called a variable gain
amplifier that modifies the output of the stock mass airflow sensor
to trick the stock computer. When he gets this working he will
be able to lean the engine and improve the MPG up to 30 MPG.
This is the number Tracy claims with his specifically design
EFI computer for aircraft use.
I returned home yesterday. I was bucking slight headwinds going back to
the west, had slight tailwinds on the original trip east. Compared to
the trip east, the days are 4 hours longer: flying east I loose 2 hours
while flying west I gain 2 hours. So I had plenty of time to throttle
back a little and take it easy. Fuel burns dropped to around 8.4 gph,
which is about what I saw last year on the flight (8.8 gph). I noticed
on the O2 sensor monitor that the engine was naturally running a little
leaner at the reduced throttle settings. The headwinds hurt the mpg
numbers so they are similar to the numbers on the trip east. This is the
data from the two longest legs:
KLBF-KLGU approx. 31 gal., 3.7 hours, 519 nm, 12,500 feet, 6000
engine RPM, 2765 prop RPM >> 8.4 gph, 16.7 nm/gal, 19.3mpg, 140 knot
average ground speed.
KLGU-KDLS approx. 30 gal., 3.6 hours, 477 nm, 10,500 feet, 5800
engine RPM, 2673 prop RPM >> 8.3 gph, 15.9 nm/gal, 18.3mpg, 133 knot
average ground speed.
Perry
Thanks for the data Perry.
If you are burning 100LL your O2 monitor may have degraded?
I think a small A to D - CPU - D to A would work better as
variable gain amp.
Paul Lamar ...No rotor no motor.
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