X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-db01.mx.aol.com ([205.188.91.95] verified) by logan.com (CommuniGate Pro SMTP 5.4.5) with ESMTP id 5548001 for flyrotary@lancaironline.net; Fri, 18 May 2012 02:03:41 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.91.95; envelope-from=Lehanover@aol.com Received: from mtaomg-da01.r1000.mx.aol.com (mtaomg-da01.r1000.mx.aol.com [172.29.51.137]) by imr-db01.mx.aol.com (8.14.1/8.14.1) with ESMTP id q4I630a6012857 for ; Fri, 18 May 2012 02:03:00 -0400 Received: from core-moa002b.r1000.mail.aol.com (core-moa002.r1000.mail.aol.com [172.29.233.5]) by mtaomg-da01.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 95CF5E000086 for ; Fri, 18 May 2012 02:03:00 -0400 (EDT) From: Lehanover@aol.com Message-ID: Date: Fri, 18 May 2012 02:03:00 -0400 (EDT) Subject: Re: [FlyRotary] Re: BSFC and EGT To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_ec70.18957ddc.3ce74014_boundary" X-Mailer: AOL 9.6 sub 5004 X-Originating-IP: [173.88.30.23] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20110426; t=1337320980; bh=ziTPy/v8qRPveggOjJ7CmCfob3MPgOStWPRbOqyKwEA=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=t4e7U4cZwNQqEu36Bs+f8HZgaG6r3dnRtGS0tkVWjjgczP8arH12bjy965JNpBs7Q pFcNQ2hvrBR1rSQQRLQWSGhZUiHI+5UIDJLezcyrvybwmjuat4qpAJZmXI7Vko/6iA YkaEXDq+UlXsBCDbLWdFq3K3ZirG1SIf99YLr6A0= X-AOL-SCOLL-SCORE: 0:2:440577216:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d33894fb5e61478f3 --part1_ec70.18957ddc.3ce74014_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Leaning and more ignition advance go together. Leaner mixtures burn slower, so advance is added to keep maximum cylinder pressure at 50 degrees after TDC. In some installations, lean cut off may be crisp with no misfires at all. More like an ignition switch turned off. The RX-8 had closed throttle maps up to 44 degrees. Adding a high energy ignition system with large plug gaps may get you further into lean burn. This would be where I would experiment with high energy on the trailing ignition and split timing events. After maximizing lean performance, I would go to higher coolant and oil temps and record those data. Lynn E. Hanover In a message dated 5/17/2012 10:55:56 A.M. Eastern Daylight Time, SBoese@uwyo.edu writes: Gordon and Ernest, The BSFC units are Lb/Hp-Hr as you expect. Around 0.6 is as low as is usually seen with my setup under normal operating conditions. I've seen as low as 0.52 with very aggressive ignition timing advance settings, but these settings probably would not be used over the long term. Generally, the engine does not run rough as it looses power when the mixture 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 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. > That was my thought, too, Gordon. I also notice that the BSFC is almost static between 0 and -175 or so. Seems to make sense. The efficiency gained by using less fuel in the mixture would be offset 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 dramatically is probably where the engine is running rough from a increasing number of misfires, all the way to the point where it won't run anymore? This again makes me wish I had added the GPIO board to my MegaSquirt, so that I could record EGT. -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html --part1_ec70.18957ddc.3ce74014_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Leaning and more ignition advance go together. Leaner mixtures bu= rn=20 slower, so advance is added to keep maximum cylinder pressure at 50 degrees= =20 after TDC. In some installations, lean cut off may be crisp with no misfire= s at=20 all. More like an ignition switch turned off.
 
The RX-8 had closed throttle maps up to 44 degrees.
 
Adding a high energy ignition system with large plug gaps may get you= =20 further into lean burn. This would be where I would experiment with high en= ergy=20 on the trailing ignition and split timing events. After maximizing lean=20 performance, I would go to higher coolant and oil temps and record those=20 data.
 
Lynn E. Hanover
 
In a message dated 5/17/2012 10:55:56 A.M. Eastern Daylight Time,=20 SBoese@uwyo.edu writes:
= Gordon=20 and Ernest,

The BSFC units are Lb/Hp-Hr as you expect.  Aroun= d 0.6=20 is as low as is usually seen with my setup under normal operating=20 conditions.  I've seen as low as 0.52 with very aggressive ignition= =20 timing advance settings, but these settings probably would not be used ov= er=20 the long term.

Generally, the engine does not run rough as it loos= es=20 power when the mixture is leaned.  Eventually, the point is reached = where=20 it just=20 dies.

Steve

________________________________________
Fro= m:=20 Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Erne= st=20 Christley [echristley@att.net]
Sent: Thursday, May 17, 2012 7:09 AMTo:=20 Rotary motors in aircraft
Subject: [FlyRotary] Re: BSFC and=20 EGT

Gordon Alling wrote:
> If I read this plot correctly, th= e SFC=20 is reported between 0.6 and 0.7 over
> most of the range.  Wha= t=20 units are used?  Lb/Hp-Hr?  If so, this seems a bit
> hig= h for=20 a four-stroke spark ignition engine at cruise setting.  I would
&= gt;=20 expect to see 0.45 - 0.55 Lb/Hp-Hr.
>

That was my thought, t= oo,=20 Gordon.  I also notice that the BSFC is almost static between 0 and = -175=20 or so.  Seems to make
sense.  The efficiency gained by using= less=20 fuel in the mixture would be offset by the efficiency lost by the=20 mixture
not being rich enough to burn completely.  That condition= =20 would hold for a bit until it gets so lean (and cold) that it
will har= dly=20 burn at all.  The bottom end where the BSFC curve shoots up dramatic= ally=20 is probably where the engine is
running rough from a increasing number= of=20 misfires, all the way to the point where it won't run anymore?

Thi= s=20 again makes me wish I had added the GPIO board to my MegaSquirt, so that = I=20 could record EGT.

--
Homepage: =20 http://www.flyrotary.com/
Archive and UnSub:  =20 http://mail.lancaironline.net:81/lists/flyrotary/List.html
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