AOPA Pilot Magazine - February 2018 - 87
THE OPTIMUM AIR/FUEL RATIOS for piston-
engine power and efficiency have been
known for decades-but aircraft engine
gauges don't display them. Pilots monitor exhaust gas temperatures, fuel flows,
and cylinder head temperatures-all indirect indications of the air/fuel ratio (AFR).
Things get even less precise when pilots
lack engine monitors and are forced to lean
the old-fashioned way: Pull the mixture
knob out until the engine runs rough, then
push it in until the engine runs smoothly
again.
There's a better way.
Many high-performance cars are
equipped with a lambda gauge that continuously displays AFR (and uses a sensor
in the exhaust manifold to measure it).
Aircraft engine manufacturers don't use
lambda gauges, but owners and builders of
Experimental-category aircraft are beginning to adopt them.
Klaus Savier, founder of Lightspeed
Engineering, a California firm that designs
and sells electronic ignition systems, says
lambda gauges take the guesswork out of
leaning. Pilots taking off from high-altitude airports can at a glance precisely set
the mixture for best power before beginning
their takeoff rolls, and pilots leveling off at
high altitude in cruise can easily and quickly
set the mixture for maximum efficiency.
"I thought about installing a lambda
gauge in my airplane many years ago,"
Savier said, "but I was told they wouldn't
work with leaded avgas, so I didn't question it, and I didn't try. Finally, I decided to
see for myself. I've been flying with lambda
gauges in my two airplanes now for a combined 800 hours.
"They're tremendously useful," he said.
"I hardly even look at [exhaust gas temperatures] anymore."
Engineers have long known that the optimum AFR for peak output is 14.7:1-and the
first gauge for measuring it in cars was developed in the late 1960s. In air-cooled piston
aircraft engines, full power at peak output
can create dangerously high temperatures, so
pilots are wise to avoid them. Piston engines
typically run at relatively rich mixture settings during takeoff and climb.
Savier says he takes off and climbs at a
best-power setting of 12.7:1. In cruise, he
typically leans for maximum efficiency at
a lean-of-peak setting of 16:1. The graphical engine monitor on his Rutan-designed
Long-EZ confirms exhaust gas and cylinder head temperatures are well within
limits.
Mike Filucci, an AOPA colleague,
installed a lambda gauge in his RV-4 and
says it's become his primary reference for
setting the mixture in his ECI Titan IO-370
engine. He documented the results on a
series of flights that showed remarkable
reductions in fuel consumption accompanied by relatively minor speed penalties.
At 9,500 feet (and a density altitude
of almost 11,000 feet), for example, a rich
AFR setting of 11 on the lambda gauge (best
power) resulted in a true airspeed of 178
knots (152 indicated) at a fuel flow of 12
gallons per hour.
Then he leaned the AFR to 16 on the
lambda gauge and airspeed dropped five
knots to 173 true (147 indicated) while fuel
flow plummeted to 7.1 gallons per hour.
That's a 3-percent airspeed reduction for
a 40-percent drop in fuel consumption.
Engine CHTs and EGTs stayed well
within normal ranges at both rich and
lean settings. (The engine was equipped
with dual P-Mag electronic ignitions and
automotive spark plugs and wiring harnesses, so it ran smoothly despite being
100 degrees Fahrenheit lean of peak EGT.)
Savier says pilots who avoid overly rich
mixture settings should expect meaningful improvements in engine efficiency and
reliability, too.
"Unburned fuel from excessively rich
mixture settings will dilute the oil and
cause ring and cylinder wear," he said.
Savier said the lead fouling caused his
first lambda probe to fail. But that problem hasn't recurred, primarily because the
information the gauge provides allows him
to run his engine far leaner-and that keeps
lead deposits from building up. Also, the
shift away in general aviation from leaded
fuels in the future may make lead fouling
a moot point.
"I only had one probe go bad," Savier
said, "and that happened early, when there
was a lot of rich operation."
AOPA
EMAIL dave.hirschman@aopa.org
www.aopa.org/pilot AOPA PILOT | 87
2018 AOPA
PILOT
GUIDES
Now Available!
ALL NEW
REDESIGN!
Buy at
flytheislands.com
http://www.flytheislands.com
http://www.aopa.org/pilot
AOPA Pilot Magazine - February 2018
Table of Contents for the Digital Edition of AOPA Pilot Magazine - February 2018
Contents
AOPA Pilot Magazine - February 2018 - Intro
AOPA Pilot Magazine - February 2018 - Cover1
AOPA Pilot Magazine - February 2018 - Cover2
AOPA Pilot Magazine - February 2018 - Contents
AOPA Pilot Magazine - February 2018 - 2
AOPA Pilot Magazine - February 2018 - 3
AOPA Pilot Magazine - February 2018 - 4
AOPA Pilot Magazine - February 2018 - 5
AOPA Pilot Magazine - February 2018 - 6
AOPA Pilot Magazine - February 2018 - 7
AOPA Pilot Magazine - February 2018 - 8
AOPA Pilot Magazine - February 2018 - 9
AOPA Pilot Magazine - February 2018 - 10
AOPA Pilot Magazine - February 2018 - 11
AOPA Pilot Magazine - February 2018 - 12
AOPA Pilot Magazine - February 2018 - 13
AOPA Pilot Magazine - February 2018 - 14
AOPA Pilot Magazine - February 2018 - 15
AOPA Pilot Magazine - February 2018 - 16
AOPA Pilot Magazine - February 2018 - 17
AOPA Pilot Magazine - February 2018 - 18
AOPA Pilot Magazine - February 2018 - 19
AOPA Pilot Magazine - February 2018 - 20
AOPA Pilot Magazine - February 2018 - 21
AOPA Pilot Magazine - February 2018 - 22
AOPA Pilot Magazine - February 2018 - 23
AOPA Pilot Magazine - February 2018 - 24
AOPA Pilot Magazine - February 2018 - 25
AOPA Pilot Magazine - February 2018 - 26
AOPA Pilot Magazine - February 2018 - 27
AOPA Pilot Magazine - February 2018 - 28
AOPA Pilot Magazine - February 2018 - 29
AOPA Pilot Magazine - February 2018 - 30
AOPA Pilot Magazine - February 2018 - 31
AOPA Pilot Magazine - February 2018 - 32
AOPA Pilot Magazine - February 2018 - 33
AOPA Pilot Magazine - February 2018 - 34
AOPA Pilot Magazine - February 2018 - 35
AOPA Pilot Magazine - February 2018 - 36
AOPA Pilot Magazine - February 2018 - 37
AOPA Pilot Magazine - February 2018 - 38
AOPA Pilot Magazine - February 2018 - 39
AOPA Pilot Magazine - February 2018 - 40
AOPA Pilot Magazine - February 2018 - 41
AOPA Pilot Magazine - February 2018 - 42
AOPA Pilot Magazine - February 2018 - 43
AOPA Pilot Magazine - February 2018 - 44
AOPA Pilot Magazine - February 2018 - 45
AOPA Pilot Magazine - February 2018 - 46
AOPA Pilot Magazine - February 2018 - 47
AOPA Pilot Magazine - February 2018 - 48
AOPA Pilot Magazine - February 2018 - 49
AOPA Pilot Magazine - February 2018 - 50
AOPA Pilot Magazine - February 2018 - 51
AOPA Pilot Magazine - February 2018 - 52
AOPA Pilot Magazine - February 2018 - 53
AOPA Pilot Magazine - February 2018 - 54
AOPA Pilot Magazine - February 2018 - 55
AOPA Pilot Magazine - February 2018 - 56
AOPA Pilot Magazine - February 2018 - 57
AOPA Pilot Magazine - February 2018 - 58
AOPA Pilot Magazine - February 2018 - 59
AOPA Pilot Magazine - February 2018 - 60
AOPA Pilot Magazine - February 2018 - 61
AOPA Pilot Magazine - February 2018 - 62
AOPA Pilot Magazine - February 2018 - 63
AOPA Pilot Magazine - February 2018 - 64
AOPA Pilot Magazine - February 2018 - 65
AOPA Pilot Magazine - February 2018 - 66
AOPA Pilot Magazine - February 2018 - 67
AOPA Pilot Magazine - February 2018 - 68
AOPA Pilot Magazine - February 2018 - 69
AOPA Pilot Magazine - February 2018 - 70
AOPA Pilot Magazine - February 2018 - 71
AOPA Pilot Magazine - February 2018 - 72
AOPA Pilot Magazine - February 2018 - 73
AOPA Pilot Magazine - February 2018 - 74
AOPA Pilot Magazine - February 2018 - 75
AOPA Pilot Magazine - February 2018 - 76
AOPA Pilot Magazine - February 2018 - 77
AOPA Pilot Magazine - February 2018 - 78
AOPA Pilot Magazine - February 2018 - 79
AOPA Pilot Magazine - February 2018 - 80
AOPA Pilot Magazine - February 2018 - 81
AOPA Pilot Magazine - February 2018 - 82
AOPA Pilot Magazine - February 2018 - 83
AOPA Pilot Magazine - February 2018 - 84
AOPA Pilot Magazine - February 2018 - 85
AOPA Pilot Magazine - February 2018 - 86
AOPA Pilot Magazine - February 2018 - 87
AOPA Pilot Magazine - February 2018 - 88
AOPA Pilot Magazine - February 2018 - 89
AOPA Pilot Magazine - February 2018 - 90
AOPA Pilot Magazine - February 2018 - 91
AOPA Pilot Magazine - February 2018 - 92
AOPA Pilot Magazine - February 2018 - 93
AOPA Pilot Magazine - February 2018 - 94
AOPA Pilot Magazine - February 2018 - 95
AOPA Pilot Magazine - February 2018 - 96
AOPA Pilot Magazine - February 2018 - 97
AOPA Pilot Magazine - February 2018 - 98
AOPA Pilot Magazine - February 2018 - 99
AOPA Pilot Magazine - February 2018 - 100
AOPA Pilot Magazine - February 2018 - 101
AOPA Pilot Magazine - February 2018 - 102
AOPA Pilot Magazine - February 2018 - 103
AOPA Pilot Magazine - February 2018 - 104
AOPA Pilot Magazine - February 2018 - 105
AOPA Pilot Magazine - February 2018 - 106
AOPA Pilot Magazine - February 2018 - 107
AOPA Pilot Magazine - February 2018 - 108
AOPA Pilot Magazine - February 2018 - 109
AOPA Pilot Magazine - February 2018 - 110
AOPA Pilot Magazine - February 2018 - 111
AOPA Pilot Magazine - February 2018 - 112
AOPA Pilot Magazine - February 2018 - Cover3
AOPA Pilot Magazine - February 2018 - Cover4
https://www.nxtbook.com/nxtbooks/aopa/pilot_202410
https://www.nxtbook.com/nxtbooks/aopa/pilot_202409
https://www.nxtbook.com/nxtbooks/aopa/pilot_202408
https://www.nxtbook.com/nxtbooks/aopa/pilot_202407
https://www.nxtbook.com/nxtbooks/aopa/pilot_202406
https://www.nxtbook.com/nxtbooks/aopa/pilot_202405
https://www.nxtbook.com/nxtbooks/aopa/pilot_202404
https://www.nxtbook.com/nxtbooks/aopa/pilot_202403
https://www.nxtbook.com/nxtbooks/aopa/pilot_202402
https://www.nxtbook.com/nxtbooks/aopa/pilot_202401
https://www.nxtbook.com/nxtbooks/aopa/pilot_202312
https://www.nxtbook.com/nxtbooks/aopa/pilot_202311
https://www.nxtbook.com/nxtbooks/aopa/pilot_202310
https://www.nxtbook.com/nxtbooks/aopa/pilot_202309
https://www.nxtbook.com/nxtbooks/aopa/pilot_202308
https://www.nxtbook.com/nxtbooks/aopa/pilot_202307
https://www.nxtbook.com/nxtbooks/aopa/pilot_202306
https://www.nxtbook.com/nxtbooks/aopa/pilot_202305
https://www.nxtbook.com/nxtbooks/aopa/pilot_202304
https://www.nxtbook.com/nxtbooks/aopa/pilot_202303
https://www.nxtbook.com/nxtbooks/aopa/pilot_202302
https://www.nxtbook.com/nxtbooks/aopa/pilot_202301
https://www.nxtbook.com/nxtbooks/aopa/pilot_202212
https://www.nxtbook.com/nxtbooks/aopa/pilot_202211
https://www.nxtbook.com/nxtbooks/aopa/pilot_202210
https://www.nxtbook.com/nxtbooks/aopa/pilot_202209
https://www.nxtbook.com/nxtbooks/aopa/pilot_202208
https://www.nxtbook.com/nxtbooks/aopa/pilot_202207
https://www.nxtbook.com/nxtbooks/aopa/pilot_202206
https://www.nxtbook.com/nxtbooks/aopa/pilot_202205
https://www.nxtbook.com/nxtbooks/aopa/pilot_202204
https://www.nxtbook.com/nxtbooks/aopa/pilot_202203
https://www.nxtbook.com/nxtbooks/aopa/pilot_202202
https://www.nxtbook.com/nxtbooks/aopa/pilot_202201
https://www.nxtbook.com/nxtbooks/aopa/pilot_202112
https://www.nxtbook.com/nxtbooks/aopa/pilot_202111
https://www.nxtbook.com/nxtbooks/aopa/pilot_202110
https://www.nxtbook.com/nxtbooks/aopa/pilot_202109
https://www.nxtbook.com/nxtbooks/aopa/pilot_202108
https://www.nxtbook.com/nxtbooks/aopa/pilot_202107
https://www.nxtbook.com/nxtbooks/aopa/pilot_202106
https://www.nxtbook.com/nxtbooks/aopa/pilot_202105
https://www.nxtbook.com/nxtbooks/aopa/pilot_202104
https://www.nxtbook.com/nxtbooks/aopa/pilot_202103
https://www.nxtbook.com/nxtbooks/aopa/pilot_202102
https://www.nxtbook.com/nxtbooks/aopa/pilot_202101
https://www.nxtbook.com/nxtbooks/aopa/pilot_202012
https://www.nxtbook.com/nxtbooks/aopa/pilot_202011
https://www.nxtbook.com/nxtbooks/aopa/pilot_202010
https://www.nxtbook.com/nxtbooks/aopa/pilot_202009
https://www.nxtbook.com/nxtbooks/aopa/pilot_202008
https://www.nxtbook.com/nxtbooks/aopa/pilot_202007
https://www.nxtbook.com/nxtbooks/aopa/pilot_202006
https://www.nxtbook.com/nxtbooks/aopa/pilot_202005
https://www.nxtbook.com/nxtbooks/aopa/pilot_202004
https://www.nxtbook.com/nxtbooks/aopa/pilot_202003
https://www.nxtbook.com/nxtbooks/aopa/pilot_202002
https://www.nxtbook.com/nxtbooks/aopa/pilot_202001
https://www.nxtbook.com/nxtbooks/aopa/pilot_201912
https://www.nxtbook.com/nxtbooks/aopa/pilot_201911
https://www.nxtbook.com/nxtbooks/aopa/pilot_201910
https://www.nxtbook.com/nxtbooks/aopa/pilot_201909
https://www.nxtbook.com/nxtbooks/aopa/pilot_201908
https://www.nxtbook.com/nxtbooks/aopa/pilot_201907
https://www.nxtbook.com/nxtbooks/aopa/pilot_201906
https://www.nxtbook.com/nxtbooks/aopa/pilot_201905
https://www.nxtbook.com/nxtbooks/aopa/pilot_201904
https://www.nxtbook.com/nxtbooks/aopa/pilot_201903
https://www.nxtbook.com/nxtbooks/aopa/pilot_201902
https://www.nxtbook.com/nxtbooks/aopa/pilot_201901
https://www.nxtbook.com/nxtbooks/aopa/pilot_201812
https://www.nxtbook.com/nxtbooks/aopa/pilot_201811
https://www.nxtbook.com/nxtbooks/aopa/pilot_201810
https://www.nxtbook.com/nxtbooks/aopa/pilot_201809
https://www.nxtbook.com/nxtbooks/aopa/pilot_201808
https://www.nxtbook.com/nxtbooks/aopa/pilot_201807
https://www.nxtbook.com/nxtbooks/aopa/pilot_201806
https://www.nxtbook.com/nxtbooks/aopa/pilot_201805
https://www.nxtbook.com/nxtbooks/aopa/pilot_201804
https://www.nxtbook.com/nxtbooks/aopa/pilot_201803
https://www.nxtbook.com/nxtbooks/aopa/pilot_201802
https://www.nxtbook.com/nxtbooks/aopa/pilot_201801
https://www.nxtbook.com/nxtbooks/aopa/pilot_201712
https://www.nxtbook.com/nxtbooks/aopa/pilot_201711
https://www.nxtbook.com/nxtbooks/aopa/pilot_201710
https://www.nxtbook.com/nxtbooks/aopa/pilot_201709
https://www.nxtbook.com/nxtbooks/aopa/pilot_201708
https://www.nxtbook.com/nxtbooks/aopa/pilot_201707
https://www.nxtbook.com/nxtbooks/aopa/pilot_201706
https://www.nxtbook.com/nxtbooks/aopa/pilot_201705
https://www.nxtbook.com/nxtbooks/aopa/pilot_201704
https://www.nxtbook.com/nxtbooks/aopa/pilot_201703
https://www.nxtbook.com/nxtbooks/aopa/pilot_201702
https://www.nxtbook.com/nxtbooks/aopa/pilot_201701
https://www.nxtbook.com/nxtbooks/aopa/pilot_201612
https://www.nxtbook.com/nxtbooks/aopa/pilot_201611
https://www.nxtbook.com/nxtbooks/aopa/pilot_201610
https://www.nxtbook.com/nxtbooks/aopa/pilot_201609
https://www.nxtbook.com/nxtbooks/aopa/pilot_201608
https://www.nxtbook.com/nxtbooks/aopa/pilot_201607
https://www.nxtbook.com/nxtbooks/aopa/pilot_201606
https://www.nxtbook.com/nxtbooks/aopa/pilot_201605
https://www.nxtbook.com/nxtbooks/aopa/pilot_201604
https://www.nxtbook.com/nxtbooks/aopa/pilot_201603
https://www.nxtbook.com/nxtbooks/aopa/pilot_201602
https://www.nxtbook.com/nxtbooks/aopa/pilot_201601
https://www.nxtbook.com/nxtbooks/aopa/pilot_201512
https://www.nxtbook.com/nxtbooks/aopa/pilot_201511
https://www.nxtbook.com/nxtbooks/aopa/pilot_201510
https://www.nxtbook.com/nxtbooks/aopa/pilot_201509
https://www.nxtbook.com/nxtbooks/aopa/pilot_201508
https://www.nxtbook.com/nxtbooks/aopa/pilot_201507
https://www.nxtbook.com/nxtbooks/aopa/pilot_201506
https://www.nxtbook.com/nxtbooks/aopa/pilot_201505
https://www.nxtbook.com/nxtbooks/aopa/pilot_201504
https://www.nxtbook.com/nxtbooks/aopa/pilot_201503
https://www.nxtbook.com/nxtbooks/aopa/pilot_201502
https://www.nxtbook.com/nxtbooks/aopa/pilot_201501
https://www.nxtbook.com/nxtbooks/aopa/pilot_201412
https://www.nxtbook.com/nxtbooks/aopa/pilot_201411
https://www.nxtbook.com/nxtbooks/aopa/pilot_201410
https://www.nxtbook.com/nxtbooks/aopa/pilot_201409
https://www.nxtbook.com/nxtbooks/aopa/pilot_201408
https://www.nxtbook.com/nxtbooks/aopa/pilot_201407
https://www.nxtbook.com/nxtbooks/aopa/pilot_201406
https://www.nxtbook.com/nxtbooks/aopa/pilot_201405
https://www.nxtbook.com/nxtbooks/aopa/pilot_201404
https://www.nxtbook.com/nxtbooks/aopa/pilot_201403
https://www.nxtbook.com/nxtbooks/aopa/pilot_201402
https://www.nxtbook.com/nxtbooks/aopa/pilot_201401
https://www.nxtbook.com/nxtbooks/aopa/pilot_201312
https://www.nxtbook.com/nxtbooks/aopa/pilot_201311
https://www.nxtbook.com/nxtbooks/aopa/pilot_201310
https://www.nxtbook.com/nxtbooks/aopa/pilot_201309
https://www.nxtbook.com/nxtbooks/aopa/pilot_201308
https://www.nxtbook.com/nxtbooks/aopa/pilot_201307
https://www.nxtbook.com/nxtbooks/aopa/pilot_201306
https://www.nxtbook.com/nxtbooks/aopa/pilot_201305
https://www.nxtbook.com/nxtbooks/aopa/pilot_201304
https://www.nxtbook.com/nxtbooks/aopa/pilot_201303
https://www.nxtbook.com/nxtbooks/aopa/pilot_201302
https://www.nxtbook.com/nxtbooks/aopa/pilot_201301
https://www.nxtbook.com/nxtbooks/aopa/pilot_201212
https://www.nxtbook.com/nxtbooks/aopa/pilot_201211
https://www.nxtbook.com/nxtbooks/aopa/pilot_201210
https://www.nxtbook.com/nxtbooks/aopa/pilot_201209
https://www.nxtbook.com/nxtbooks/aopa/pilot_201208
https://www.nxtbook.com/nxtbooks/aopa/pilot_201207
https://www.nxtbook.com/nxtbooks/aopa/pilot_201206
https://www.nxtbook.com/nxtbooks/aopa/pilot_201205
https://www.nxtbook.com/nxtbooks/aopa/pilot_201204
https://www.nxtbook.com/nxtbooks/aopa/pilot_201203
https://www.nxtbook.com/nxtbooks/aopa/pilot_201202
https://www.nxtbook.com/nxtbooks/aopa/pilot_201201
https://www.nxtbook.com/nxtbooks/aopa/pilot_201112
https://www.nxtbook.com/nxtbooks/aopa/pilot_201111
https://www.nxtbook.com/nxtbooks/aopa/pilot_201110
https://www.nxtbook.com/nxtbooks/aopa/pilot_201109
https://www.nxtbook.com/nxtbooks/aopa/pilot_201108
https://www.nxtbook.com/nxtbooks/aopa/pilot_201107
https://www.nxtbook.com/nxtbooks/aopa/pilot_201106
https://www.nxtbook.com/nxtbooks/aopa/pilot_201105
https://www.nxtbook.com/nxtbooks/aopa/pilot_201104
https://www.nxtbook.com/nxtbooks/aopa/pilot_201103
https://www.nxtbook.com/nxtbooks/aopa/pilot_201103_test
https://www.nxtbook.com/nxtbooks/aopa/pilot_201102
https://www.nxtbook.com/nxtbooks/aopa/pilot_201011demo
https://www.nxtbook.com/nxtbooks/aopa/pilot_201011
https://www.nxtbook.com/nxtbooks/aopa/pilot0308
https://www.nxtbookmedia.com