X-Virus-Scanned: clean according to Sophos on Logan.com
Return-Path: <marv@lancaironline.net>
Sender: <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Wed, 28 Dec 2005 22:50:25 -0500
Message-ID: <redirect-904634@logan.com>
X-Original-Return-Path: <ronlaughlin@gmail.com>
Received: from zproxy.gmail.com ([64.233.162.197] verified)
  by logan.com (CommuniGate Pro SMTP 5.0.5)
  with ESMTP id 903785 for lml@lancaironline.net; Wed, 28 Dec 2005 08:24:22 -0500
Received-SPF: pass
 receiver=logan.com; client-ip=64.233.162.197; envelope-from=ronlaughlin@gmail.com
Received: by zproxy.gmail.com with SMTP id 16so1495209nzp
        for <lml@lancaironline.net>; Wed, 28 Dec 2005 05:23:36 -0800 (PST)
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
        s=beta; d=gmail.com;
        h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references;
        b=OdW1iDM5N/b4LAYVRH95g1h661/VvNsCJ6ldNHUWrvM8U44INI3borSRh+xzaQ4I560oT7RiZiM6/EziVsP7MkznqAJwKHRwEJKI33Mwl/jZazXtO3s/Jj/u/hBfNCarQrvxNfj9DyvywVB5VQ23DQp9ZLp4pn8nuJPMhDgKOJY=
Received: by 10.65.124.7 with SMTP id b7mr2407616qbn;
        Wed, 28 Dec 2005 05:23:36 -0800 (PST)
Received: by 10.65.204.2 with HTTP; Wed, 28 Dec 2005 05:23:35 -0800 (PST)
X-Original-Message-ID: <6412e9f20512280523m6174aeb6q592203c0f59aa62f@mail.gmail.com>
X-Original-Date: Wed, 28 Dec 2005 07:23:35 -0600
From: Ron Laughlin <ronlaughlin@gmail.com>
X-Original-To: Lancair Mailing List <lml@lancaironline.net>
Subject: Re: [LML] Re: Where has all the power gone?
In-Reply-To: <list-902374@logan.com>
MIME-Version: 1.0
Content-Type: multipart/alternative; 
	boundary="----=_Part_58608_15415732.1135776215963"
References: <list-902374@logan.com>

------=_Part_58608_15415732.1135776215963
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

> Aircraft engines have dual ignition systems for increased detonation
> margins, NOT for reliability from redundancy. Aircraft combustion chamber=
s
> are so freaking big that by the time a flame front has traversed the cham=
ber
> the remaining gas has been compressed and heated to the point of
> detonation.  Starting the fire in two places shortens the combustion time
> significantly and reduces the opportunity for detonation. This is also th=
e
> mechanism for the RPM drop during a mag check.  When you turn off one mag
> the combustion event takes longer which has a similar effect as starting =
the
> process later, AKA "retarding the timing".



Hi Brent,

From what little I know about the combustion process, the above paragraph
seems to contradict it's self. Retarding the spark timing helps to prevent
detonation. If turning off one mag has the same effect as retarding the
timing (as you stated above), wouldn't running on one mag help to prevent
detonation rather than contribute to it? After all, peak cylinder pressure
will be lower while running on one mag and thetaPP will move further away
from TDC. Lower pressure means lower CHT's which should also improve
the detonation margin. I think redundancy and improved fuel efficiency may
be the reason two mags are used on aircraft engines.

--
Ron Laughlin
Legacy N44L (res)

------=_Part_58608_15415732.1135776215963
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

<br>
<div>
<blockquote class=3D"gmail_quote" style=3D"PADDING-LEFT: 1ex; MARGIN: 0px 0=
px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><font face=3D"Arial">Aircraft en=
gines have dual ignition systems for increased detonation margins, NOT for =
reliability from redundancy. Aircraft combustion chambers are so freaking b=
ig that by the time a flame front has traversed the chamber the remaining g=
as has been compressed and heated to the point of detonation.&nbsp; Startin=
g the fire in two places shortens the combustion time significantly and red=
uces the opportunity for detonation. This is also the mechanism for the RPM=
 drop during a mag check.&nbsp; When you turn off one mag the combustion ev=
ent takes longer which has a similar effect as starting the process later, =
AKA &quot;retarding the timing&quot;.&nbsp;=20
</font></blockquote>
<div><br>&nbsp;</div></div>
<div>Hi Brent,</div>
<div>&nbsp;</div>
<div>From what little I know about the combustion process, the above paragr=
aph seems to contradict it's self. Retarding the spark timing helps to prev=
ent detonation. If turning off one mag has the same effect as retarding the=
 timing (as you stated above), wouldn't running on one mag help to prevent =
detonation rather than contribute to it? After all, peak cylinder pressure =
will be lower while running on one mag and thetaPP will move further away f=
rom TDC. Lower pressure means lower CHT's&nbsp;which should also&nbsp;impro=
ve the&nbsp;detonation margin. I think redundancy and improved fuel efficie=
ncy may be the reason&nbsp;two mags are used&nbsp;on aircraft engines.
</div>
<div><br>-- <br>Ron Laughlin<br>Legacy N44L (res) </div>

------=_Part_58608_15415732.1135776215963--