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From: "Gordon Alling" <gordon@acumen-ea.com>
To: "'Rotary motors in aircraft'" <flyrotary@lancaironline.net>
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Subject: RE: [FlyRotary] BSFC and EGT
Date: Thu, 17 May 2012 08:20:38 -0400
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If I read this plot correctly, the SFC is reported between 0.6 and 0.7 over
most of the range.  What units are used?  Lb/Hp-Hr?  If so, this seems a bit
high for a four-stroke spark ignition engine at cruise setting.  I would
expect to see 0.45 - 0.55 Lb/Hp-Hr.

Gordon C. Alling, Jr., PE
President
acumen Engineering/Analysis, Inc.

540-786-2200
www.acumen-ea.com

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Steven W. Boese
Sent: Thursday, May 17, 2012 12:34 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] BSFC and EGT

Charlie and Ernest,

The attached plot is from Doug Dempsey's presentation at Paducah in 2010.
There was no wideband O2 sensor instrumentation in the system.

Steve

________________________________________
From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of
Ernest Christley [echristley@att.net]
Sent: Wednesday, May 16, 2012 9:15 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Why Apha N??  : [FlyRotary] Re: With great power
comes...the ability to muck things up

The most efficient mixture with half throttle will produce about half the
power of the most efficient mixture with full throttle.  The mixture is no
more powerful, but there is more of it. There is more fuel being
injected...twice as much, but there is also twice as much air.

The target AFR up to full throttle is not just about efficiency.  Keeping
the EGT low, noise down and exhaust clean are also considerations.

That said,  I too would be interested in any data Steve has.  Adjusting the
target AFR is fairly easy once I have a running system.

>Hi Earnest,
>
>I don't want to (mis)quote Steve Boese, but I think he did some 
>research on the most efficient point to run the mixture, & I think it 
>was something near 50 degrees lean of peak. Leaner meant less fuel 
>efficiency. (Steve?) Does that conflict with what you're planning? It 
>sounds like you could be running at much leaner than that in some 
>situations, and there doesn't seem to be a provision to vary rpm while 
>maintaining the most efficient mixture point.
>
>Am I missing something?
>
>Charlie