X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 10 Feb 2009 00:50:05 -0500 Message-ID: X-Original-Return-Path: Received: from QMTA06.emeryville.ca.mail.comcast.net ([76.96.30.56] verified) by logan.com (CommuniGate Pro SMTP 5.2.12) with ESMTP id 3483363 for lml@lancaironline.net; Sun, 08 Feb 2009 21:49:10 -0500 Received-SPF: pass receiver=logan.com; client-ip=76.96.30.56; envelope-from=j.hafen@comcast.net Received: from OMTA02.emeryville.ca.mail.comcast.net ([76.96.30.19]) by QMTA06.emeryville.ca.mail.comcast.net with comcast id DSyD1b00B0QkzPwA6eobgz; Mon, 09 Feb 2009 02:48:35 +0000 Received: from [10.0.1.199] ([98.247.31.160]) by OMTA02.emeryville.ca.mail.comcast.net with comcast id Deoa1b00T3THFyS8NeoaGh; Mon, 09 Feb 2009 02:48:35 +0000 User-Agent: Microsoft-Entourage/12.15.0.081119 X-Original-Date: Sun, 08 Feb 2009 18:48:34 -0800 Subject: Re: [LML] Re: cylinder wear-to lean or not too lean From: John Hafen X-Original-To: Lancair Mailing List X-Original-Message-ID: Thread-Topic: [LML] Re: cylinder wear-to lean or not too lean Thread-Index: AcmKYOYt0+frjnVAl0iiWxAjYYp2OQ== In-Reply-To: Mime-version: 1.0 Content-type: multipart/alternative; boundary="B_3316963715_948464" > This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. --B_3316963715_948464 Content-type: text/plain; charset="ISO-8859-1" Content-transfer-encoding: quoted-printable Here=B9s the quote: =B3So as the mixture is leaned, power peaks first, with CHT peaking at very close to the same point. In practical terms, if we lean to max CHT, we'll have max power for that MP/RPM setting. Doesn't that make sense, intuitively? Max power, max CHT? It's not precisely true, but it's close enough.=B2 John On 2/8/09 11:23 AM, "Colyn Case at earthlink" wrote: > John, > Did they really print that about CHT? > I don't remember that max CHT equates to anything useful although it = may > correlate very well to max internal cylinder pressure (ICP), which is a b= ad > thing. ...but it's also affected by cylinder cooling, while EGT is (most= ly) > not. Max EGT would be stoichiometric which is most efficient if your engi= ne > can take it. Usually slightly rich of that (e.g. 50 dF ROP) is better p= ower > but also involves more pressure before top dead center and is close to ma= x > ICP. > There's a really scary picture you get early in the APS course which = shows > how the internal cylinder pressure varies in relation to crank position w= hen > you are running at "best power". A measurable amount of the combustion > expansion is actually pushing backwards on the crank until it comes over = the > top. Great for torsional stress. > =20 > Colyn > =20 >=20 --B_3316963715_948464 Content-type: text/html; charset="ISO-8859-1" Content-transfer-encoding: quoted-printable Re: [LML] Re: cylinder wear-to lean or not too lean Here’s the quote:

“So as the mixture is leaned, power peaks first, with CHT peaking at very= close to the same point. In practical terms, if we lean to max CHT, we'll h= ave max power for that MP/RPM setting. Doesn't that make sense, intuitively?= Max power, max CHT? It's not precisely true, but it's close enough.&= #8221;

John


On 2/8/09 11:23 AM, "Colyn Case at earthlink" <colyncase@earthlink.net> wrote:

J= ohn,
    Did they really print that about CHT?
    I don't remember that max CHT equates to anything u= seful although it may correlate very well to max internal cylinder pressure = (ICP), which is a bad thing.  ...but it's also affected by cylinder coo= ling, while EGT is (mostly) not. Max EGT would be stoichiometric which is mo= st efficient if your engine can take it.   Usually slightly rich o= f that (e.g. 50 dF ROP) is better power but also involves more pressure befo= re top dead center and is close to max ICP.
    There's a really scary picture you get early in the= APS course which shows how the internal cylinder pressure varies in relatio= n to crank position when you are running at "best power".  A = measurable amount of the combustion expansion is actually pushing backwards = on the crank until it comes over the top.   Great for torsional st= ress.
Colyn

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