X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 10 Feb 2009 13:32:07 -0500 Message-ID: X-Original-Return-Path: Received: from elasmtp-curtail.atl.sa.earthlink.net ([209.86.89.64] verified) by logan.com (CommuniGate Pro SMTP 5.2.12) with ESMTP id 3485615 for lml@lancaironline.net; Tue, 10 Feb 2009 07:58:11 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.64; envelope-from=douglasbrunner@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=XBracJsBhvJ+vyREgRUqH6bTNCP2+iXf6V++suU3YAgSm5cb75/+Oq63UZd+GfDH; h=Received:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE:X-ELNK-Trace:X-Originating-IP; Received: from [74.93.196.177] (helo=DougsLaptop) by elasmtp-curtail.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1LWsBE-00088N-5r for lml@lancaironline.net; Tue, 10 Feb 2009 07:57:36 -0500 X-Original-Message-ID: <6EBF4F7B9ED74E3E8D861AA800112C16@DougsLaptop> From: "Douglas Brunner" X-Original-To: "Lancair Mailing List" References: In-Reply-To: Subject: Re: [LML] Re: cylinder wear-to lean or not too lean X-Original-Date: Tue, 10 Feb 2009 07:55:57 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0063_01C98B55.01931FF0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6001.18000 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6001.18049 X-ELNK-Trace: ad85a799c4f5de37c2eb1477c196d22294f5150ab1c16ac060844222a69b33f4eca2dcad6702ed0c6995315ec6b715fa350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 74.93.196.177 This is a multi-part message in MIME format. ------=_NextPart_000_0063_01C98B55.01931FF0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: [LML] Re: cylinder wear-to lean or not too leanHere is what I was = taught by Braly et al a.. Max power is at approximately 80 to 100 degrees rich of peak b.. Max CHT and Intra Cylinder Pressure is approximately 50 degrees = rich of peak c.. In a situation in which you are at or above 70% power (takeoff and = climb), you want to be well more than 100 ROP or conversely very lean. = However since the power curve is broader on the rich side, it is easier = to manage the engine rich. d.. You have no reason to be at 50 ROP (max CHT) - it is neither peak = power nor peak efficiency. It is also the most stressful/damaging place = to operate the engine. e.. Flying lean of peak costs you about 3 knots and saves you about 3 = gallons/hr - a very good deal in my opinion. D. Brunner (I have drunk the GAMI Koolaid) ----- Original Message -----=20 From: John Hafen=20 To: lml@lancaironline.net=20 Sent: Tuesday, February 10, 2009 12:50 AM Subject: [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 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." 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 bad thing. ...but it's also affected by cylinder = cooling, while EGT is (mostly) not. Max EGT would be stoichiometric = which is most efficient if your engine can take it. Usually slightly = rich of that (e.g. 50 dF ROP) is better power but also involves more = pressure before 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 relation 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 stress. Colyn ------=_NextPart_000_0063_01C98B55.01931FF0 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 is what I was taught by Braly et=20 al
  • Max power is at approximately 80 to = 100 degrees=20 rich of peak
  • Max CHT and Intra Cylinder Pressure is = approximately 50 degrees rich of peak
  • In a situation in which you are at or = above 70%=20 power (takeoff and climb), you want to be well more than 100 ROP or = conversely=20 very lean.  However since the power curve is broader on the rich = side, it=20 is easier to manage the engine rich.
  • You have no reason to be at 50 ROP = (max=20 CHT) - it is neither peak power nor peak efficiency.  It is = also the=20 most stressful/damaging place to operate the engine.
  • Flying lean of peak costs you about 3 = knots and=20 saves you about 3 gallons/hr - a very good deal in my = opinion.
D. Brunner
 
(I have drunk the = GAMI Koolaid)
----- Original Message -----
From:=20 John Hafen=20
Sent: Tuesday, February 10, = 2009 12:50=20 AM
Subject: [LML] Re: cylinder = wear-to lean=20 or not too lean

Here=92s the = quote:

=93So as the = mixture is=20 leaned, power peaks first, with CHT peaking at very close to the same = point.=20 In practical terms, if we lean to max CHT, we'll have max power for = that=20 MP/RPM setting. Doesn't that make sense, intuitively? Max power, max = CHT? It's=20 not precisely true, but it's close=20 enough.=94

John


On 2/8/09 11:23 AM, "Colyn Case at = earthlink"=20 <colyncase@earthlink.net>=20 wrote:

John,
    Did they really print = that about=20 CHT?
    I don't remember that max CHT = equates to=20 anything useful although it may correlate very well to max internal = cylinder=20 pressure (ICP), which is a bad thing.  ...but it's also = affected by=20 cylinder cooling, while EGT is (mostly) not. Max EGT would be = stoichiometric=20 which is most efficient if your engine can take it. =   Usually=20 slightly rich of that (e.g. 50 dF ROP) is better power but also = involves=20 more pressure before top dead center and is close to max=20 ICP.
    There's a really scary picture you = get early=20 in the APS course which shows how the internal cylinder pressure = varies in=20 relation to crank position when you are running at "best power". =  A=20 measurable amount of the combustion expansion is actually pushing = backwards=20 on the crank until it comes over the top.   Great for = torsional=20 stress.

Colyn


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