Apparently that works even though the mixture has been leaned?

Yes, it does as it is a mechanical linkage.

Walter,

 

Yesterday I went out for another test flight. I am not going to reproduce the data detail I collected here because I want to do it again under better controls. 

 

In general, @6500 MSL, @WOT the first 100 RPM reduction gave me about a 7.5% increase in FF, a 1% reduction in TAS and, interestingly, a 90F drop in EGT.  The next 100 RPM drop (to 2300) had the same FF as 25x2500, with a 3% reduction in TAS (from the 25x25 speed) and, unfortunately, I did not record the EGT.  Looks like the fuel flow went rich (I did not touch the mixture)?

 

Back at 25x2500, I dropped the MAP 1" and the FF dropped about 8.5%, TAS about .5% and there was a 50F rise in EGT.  The next MAP reduction of 1" (to 23") had a FF drop of 15% (from 25x2500), TAS drop of 3% and a 40F increase in EGT.  Looks like the FF went lean?

 

Even though I was in smooth air, heading WNW with the AP locked on track and altitude, the Km GS readings followed the TAS trend but were all over the place in magnitude - Maybe I changed air mass although the current weather map showing fronts would make be think not?  Of course, I was almost to the Mississippi before I looked out the window and turned back.

 

If I were to repeat this experiment, I would re-lean each power change for say, best power at 100F ROP.  At the throttle reduction from WOT, maybe I should back the throttle down until the MAP just begins to drop, then slowly put the MAP back at the WOT reading without the throttle being firewalled (thus, eliminating auto rich), then lean for best power.  Maybe I should use this as the WOTx2500 base line.  Does this make sense?  Any suggestions?

 

While this is fun for me, I wish someone with a more accurate in flight engine data monitor would likewise run these experiments in their Lancair Lawn Dart.