David-aviator
Well Known Member
Today was the first time I had a chance to climb to 8500' and let the airplane run out at WOT since the cowl finish job. Last month the engine wound up to 2690 rpm which I felt was a bit anemic, TAS also seemed a bit slow, like 163 knots as I recall. Today was quite different. The engine wound up to 2800 at 12.2 gph and as near as I can tell, the TAS was 172 knots (or in marketing terms, 198 mph). Van's advertises 203 mph for the 7A at 8000' with a CS 2 blade prop so this machine is in the same ball park, finally.
After the WOT run, I reset 8 gph, my usual cross country planning number and was pleased to see 152 KTAS (or 175 mph). RPM was 2540, MP 19.8, CHT 386, EGT 1436, OT 170 and OP 71. Power is about 52% with very reasonable numbers. The engine should run forever.
I am not about to suggest the cowl is in laminar flow, but it sure is less drag than when it was about half raw unfinished fiber glass. Smooth paint really makes a difference. Another item is ram air into the FM200 AFP fuel controller. It boosts MP from 19.3 to 19.8 at 8500 and rpm goes up from 2510 to 2540 burning 8 gph. It is becoming habit to open ram air when climbing through 1500', the engine does perform better, and closing it when the boost pump is turned on for landing. (MP at WOT was 23 inches)
The EIS 4000 fuel flow calibration is also about right . Calculated add was 21.3 and actual was 20.6. That .7 gallons can be accounted for with the purge valve by-pass feature. If anyone is interested - the Flocal number in this set up is 170.
Pierre suggested using 1900 rpm on down wind to get this pony under control for landing and 1400 turning final. I tried it today at 3 airports and it works quite well, at least better than driving in at 2500 rpm and 140 IAS. You can not do a slam dunk with this machine as was routine with the Subby and MT. Max final airspeed for me is 70 KTAS, if you go into the flare at 90, the machine will float 3000' in a calm wind.
After the WOT run, I reset 8 gph, my usual cross country planning number and was pleased to see 152 KTAS (or 175 mph). RPM was 2540, MP 19.8, CHT 386, EGT 1436, OT 170 and OP 71. Power is about 52% with very reasonable numbers. The engine should run forever.
I am not about to suggest the cowl is in laminar flow, but it sure is less drag than when it was about half raw unfinished fiber glass. Smooth paint really makes a difference. Another item is ram air into the FM200 AFP fuel controller. It boosts MP from 19.3 to 19.8 at 8500 and rpm goes up from 2510 to 2540 burning 8 gph. It is becoming habit to open ram air when climbing through 1500', the engine does perform better, and closing it when the boost pump is turned on for landing. (MP at WOT was 23 inches)
The EIS 4000 fuel flow calibration is also about right . Calculated add was 21.3 and actual was 20.6. That .7 gallons can be accounted for with the purge valve by-pass feature. If anyone is interested - the Flocal number in this set up is 170.
Pierre suggested using 1900 rpm on down wind to get this pony under control for landing and 1400 turning final. I tried it today at 3 airports and it works quite well, at least better than driving in at 2500 rpm and 140 IAS. You can not do a slam dunk with this machine as was routine with the Subby and MT. Max final airspeed for me is 70 KTAS, if you go into the flare at 90, the machine will float 3000' in a calm wind.