Mailing List flyrotary@lancaironline.net Message #25113
From: Russell Duffy <13brv3@bellsouth.net>
Subject: RE: [FlyRotary] Re: EM-2 and fuel flow questions
Date: Mon, 18 Jul 2005 21:27:35 -0500
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>
Message
Yes it matters and the EC2 tries to estimate BSFC if you have an O2 sensor attached.  The BSFC constant in the EC2 is the median at 14.7 : 1.  This is all just my best guesses so don't sue me if you don't get lab grade results right off the bat.  Juggle BSFC factor in the EC2 if you need to. 
 
I didn't realize that the EM-2 (I presume you really do mean EM-2, not EC-2) did that much estimating of the BSFC.  I also forgot that the BSFC was one of the parameters.  I got the .55 number from another site, so I guess it's probably right.  I also noticed today that the EM-2 manual lists the BSFC constant as "best power mixture", but you just said it's at 14.7, so I'm still confused.  
 
The calculated HP displayed is based on Fuel flow and calculated BSFC.  The % power is based on   calculated HP divided by the max HP factor.  If you rate the engine lower in max HP, you could see more than 100% power displayed.  
 
OK, that helps.  I used to see more than 100% often.  Some of that was due to the fact that my smaller injectors and uncalibrated fuel flow made it appear that I hade more fuel flow than I did.   I also had the max HP listed at 186, when it's probably at least 200 in the 7k range.  I now have the max HP set at 200, and changed the FF cal constant from 145 to 178 today.  That should get me in the ballpark, and I can start keeping track of fuel to fine tune it.  
 
This is based on a calculation involving how long John is laid up and unable to fly and how many times I have to sabotage Buly's EC2.  :- )))) 
 
Great answer :-)
 
Thanks,
Rusty (It's always John's fault) 
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