You gave a pretty good list of parameters so I think I can make a pretty good guess, especially since you used the same TB throat size as I did.  (side note:   I think the "bigger is better" approach is the wrong way to go.  There is another rotary advocate recommending a 4 inch or larger TB. )

 

I'm going from memory here but it seems that at cruise altitude I'm using about 2/3 travel on throttle quadrant (econo cruise).  Down at sea level this same setting is a lot more power.   As you pointed out, there is no single answer but if the throttle were 40 - 50% open, you could fly most anywhere safely and comfortably. 

 

Thanks, Tracy. I was hoping there would be someone out there flying with the same TB diameters.

 

Like most things, TB diameter is a tradeoff.  My conclusion from the dyno data is that 44mm per rotor (1 ¾) is a bit small as the MAP is dropping off over 5000 RPM.  But if you want to idle at 1500, and have a decent transition from there to 3000; 1 ¾ is good.  For a 2.85 to redrive, I’d want to increase that flow area by 30% or so – to about 2” dia for each rotor.

 

My data may not be representative because of restricted flow to the TB.  The ‘airbox’ size is restricted by the cowl, and may have restricted the flow a bit.  In hindsight, it would have been smart (and easy) to make a run with the airbox off and see what difference it made.

 

Al