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From: "Steven W. Boese" <SBoese@uwyo.edu>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: RE: [FlyRotary] Re: BSFC and EGT
Thread-Topic: [FlyRotary] Re: BSFC and EGT
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Date: Thu, 17 May 2012 14:53:54 +0000
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Gordon and Ernest,

The BSFC units are Lb/Hp-Hr as you expect.  Around 0.6 is as low as is usua=
lly seen with my setup under normal operating conditions.  I've seen as low=
 as 0.52 with very agressive ignition timing advance settings, but these se=
ttings probably would not be used over the long term.

Generally, the engine does not run rough as it looses power when the mixtur=
e is leaned.  Eventually, the point is reached where it just dies.

Steve

________________________________________
From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of =
Ernest Christley [echristley@att.net]
Sent: Thursday, May 17, 2012 7:09 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: BSFC and EGT

Gordon Alling wrote:
> If I read this plot correctly, the SFC is reported between 0.6 and 0.7 ov=
er
> 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.
>

That was my thought, too, Gordon.  I also notice that the BSFC is almost st=
atic between 0 and -175 or so.  Seems to make
sense.  The efficiency gained by using less fuel in the mixture would be of=
fset by the efficiency lost by the mixture
not being rich enough to burn completely.  That condition would hold for a =
bit until it gets so lean (and cold) that it
will hardly burn at all.  The bottom end where the BSFC curve shoots up dra=
matically is probably where the engine is
running rough from a increasing number of misfires, all the way to the poin=
t where it won't run anymore?

This again makes me wish I had added the GPIO board to my MegaSquirt, so th=
at I could record EGT.

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