Steve,
Lycomings Part Throttle Fuel Consumption graph on page 3-22 of my manual shows at 5.5 g/h and 2,000 rpm (from your graph) and a very lean mixture (best economy/peak egt or leaner) would give 80 hp (I assume it is 160 hp engine?).
Sig, yes I would rather a little over rich than lean on full power, though as you see I use it minimally. I had it richer but decided I wanted it a little closer to the Lyco spec., but it was a feeling rather than any good justification. Wanting it richer than Lyco indicate makes sense because at full power the distribution is very poor, though as you see when leaned right out everything closes up nicely.
Fin, yes it is nominally 160hp though Bart said a little more. But I expect you are about right.
A very interesting thing shows up though in that last graph.
I will repeat it here. I try to run at,
2000rpm
21lph
22", not because it is easy to remember but because I have noticed it to be very economic. If you look at the graph, up until just after 9:28 I am actually running with about 22lph. (Its very hard to adjust) Then I get it right.
Several things happen:
- The grey line at the top is a computed MPG and you see it jumps up from around 7 to perhaps 7.3.
Clearly the efficiency has increased with less fuel.
- the speed is unchanged. (I can get leaner still, 19lph, but then the speed drops away fast.)
- The EGT tighten right up.
- The CHT actually widen out slightly with #1 dropping faster than the others.
On the return flight I set the fuel flow up but in fact it is running more like 20.5lph. The MPG clearly increases but in fact the airspeed has already dropped a little. Perhaps 4 to 5mph on average though the air was quite turbulent. (Which will cause me to raise another post.)