You can download the PPT from the APS website.
Best Power is 75˚ ROP. It will not be slower than 50dF ROP. I suspect something is amiss in your method or measure. The TAS difference between that and 50dF ROP will be very hard to measure--maybe a knot. Best economy mixture changes depending on the power setting. At 60%, it's around 10dF LOP. At 85% power, it's about 80-90dF LOP with straight line interpolation possible.
In the example you presented, the optimal LOP mixture would be about 15dF LOP. You are not hurting anything, but have leaned further than optimal and are giving up performance when LOP.
The difference between Best Power and best economy at 7k feet (NA leaned optimally) would be about 3 gph for a 3 knot loss in IAS.
BTW, 50dF ROP and 50dF LOP should be the same number. Yours were close. The difference was probably in finding peak form the rich and lean sides. The fact that you noted a 9 knots difference is proof that the LOP mixture was leaner than optimal. The 40dF diff in CHT is as expected.
You notice that 100˚ ROP was the same speed as 50˚ ROP is correct. They should be so close to the same as to be essentially immeasurable in flight!
On Oct 24, 2013, at 10:47 AM, George Wehrung wrote:
Does anyone have a copy of the powerpoint presentation from the advanced pilot seminar? I ask because I think for our plane running 50˚ ROP gives us the best performance. 50˚ LOP is the best fuel economy.
I have been collecting data especially on my cross country trip for our IO 550.
Basically at 7,000 feet I found that at 50˚ LOP I was indicating 170 KTS TAS and 150 KIAS.
At 50˚ ROP I was 179 TAS and 158 KIAS.
My EGTs/CHTs: 291/1435 LOP & 330/1431 ROP.
When I tried 75˚ ROP I slowed a couple of knots. At 100˚ was increased fuel consumption for no gain in airspeed.
Anyhow, I pasted some data below which was typical for the 9 leg trip across the US last week for our ferry flight. Also note, the plane is not painted, which may bear differences for our ES vs others.
7000
|
2400
|
150
|
170
|
12.7
|
291
|
1435
|
50˚ LOP
|
7000
|
2400
|
158
|
179
|
16.6
|
330
|
1431
|
50˚ ROP
|
7000
|
2400
|
157
|
177
|
16.8
|
332
|
1416
|
75˚ ROP
|
7000
|
2400
|
157
|
177
|
17.3
|
331
|
1391
|
100˚ ROP
|