X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 24 Oct 2013 09:07:14 -0400 Message-ID: X-Original-Return-Path: Received: from nm5-vm1.bullet.mail.ne1.yahoo.com ([98.138.91.32] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTPS id 6562524 for lml@lancaironline.net; Thu, 24 Oct 2013 06:02:53 -0400 Received-SPF: none receiver=logan.com; client-ip=98.138.91.32; envelope-from=casey.gary@yahoo.com Received: from [98.138.90.48] by nm5.bullet.mail.ne1.yahoo.com with NNFMP; 24 Oct 2013 10:02:18 -0000 Received: from [98.138.89.168] by tm1.bullet.mail.ne1.yahoo.com with NNFMP; 24 Oct 2013 10:02:18 -0000 Received: from [127.0.0.1] by omp1024.mail.ne1.yahoo.com with NNFMP; 24 Oct 2013 10:02:18 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 24424.90201.bm@omp1024.mail.ne1.yahoo.com Received: (qmail 92971 invoked by uid 60001); 24 Oct 2013 10:02:17 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Rocket-MIMEInfo:X-Mailer:Message-ID:Date:From:Reply-To:Subject:To:MIME-Version:Content-Type; b=ulWVn879oemq7iCjyPcFmmESyaXNXjr2UiI5cVnIkEXLHabTXvBH3++8a59m3EWiYSwP01fCYJaNWZq0R9EzONmLCe4A0/dfnt3qmsmIuNVzET80/hAVGRDk6Hl1p6lhrsr2F54DIa2JY6SO5yAmPgGEhlN4xtwV2kItDIvV6UM=; X-YMail-OSG: 79K3m8QVM1nR.ijCqtxtUv7ok9Eq51ly5fJ5g25QSqtkaQ0 pMjeC6mrVWatoLlxs8TDP4uU83wkpmVnfgCt9aGTDGpso.BWYtAyxmvDRdEh gWtQAdMUvNYkzeR8GigcDm0VGRUbwptuX6i0v4tHcq1qW7aWUXI9U_iurNxT nUaJZNBjJUawqUpgbEvCZzY_ATpKar20VunF_xzBJrJE0rvOiHSmwpPzX8EA 5dj_F.xWH5qo5v_rXdn9fDsstodGBW8luF2P3jBQemfYrQFgOCs.hunRWs0W yoRzLmdScEXJw108r09DDqefhmpw.vaX5DRSels4uRqOruSOXTY_CihZNM20 .O4nfRg3OIjt05HjTbxy7eVZRr.VQk4.D1ard82fTAgCVId84xjtXHQMv3RC .FY89u86WpHjr4GHJACtMSEK.09xCzANhoTXiv32AC69S6UsifD0pkP_2pb2 Orq9PjKwLjdGNzus3GXMLpVJ3b2n7DECdsLJakRGQiuGL5LBMs0gRxSkA.As EeqH_bEvsiAMUa6Ggbz.MWRvXkXXyc0SAUu2SZsuofjZSimKTJvcgluq_n0s xCYstcHjvh7vJ0APwqQ-- Received: from [97.92.63.83] by web120106.mail.ne1.yahoo.com via HTTP; Thu, 24 Oct 2013 03:02:17 PDT X-Rocket-MIMEInfo: 002.001,SXQgaXMgd2l0aCBncmVhdCByZWx1Y3RhbmNlIHRoYXQgSSB3b3VsZCBjb250cmFkaWN0IC0gb3IgZXZlbiBxdWVzdGlvbiAtIGFueXRoaW5nIHNhaWQgYnkgV2FsdGVyLCBidXQgaGVyZSBnb2VzLi4uCgoKSSBzYWlkOgoKVGhlIHNsb3dlciBidXJuIHJhdGUgb24gb25lIHBsdWcgbWVhbnMgdGhhdCBhIHNpZ25pZmljYW50IHBvcnRpb24gb2YgdGhlID0KYnVybiBoYXBwZW5zIGR1cmluZyB0aGUgZXhwYW5zaW9uIHN0cm9rZSBhbmQgbGVzcyBoZWF0IGlzIGNvbnZlcnRlZCB0byA9CnBvd2VyLiA9MjAKCldhbHQBMAEBAQE- X-Mailer: YahooMailWebService/0.8.160.587 X-Original-Message-ID: <1382608937.90376.YahooMailNeo@web120106.mail.ne1.yahoo.com> X-Original-Date: Thu, 24 Oct 2013 03:02:17 -0700 (PDT) From: Gary Casey Reply-To: Gary Casey Subject: Re: [LML] Hot TITs on X country leg. LIVP X-Original-To: Lancair Mailing List MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-96787742-1451441967-1382608937=:90376" ---96787742-1451441967-1382608937=:90376 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable It is with great reluctance that I would contradict - or even question - an= ything said by Walter, but here goes...=0A=0A=0AI said:=0A=0AThe slower bur= n rate on one plug means that a significant portion of the =3D=0Aburn happe= ns during the expansion stroke and less heat is converted to =3D=0Apower. = =3D20=0A=0AWalter replied:=0AUh, not really.=A0 You can actually end up wit= h MORE power, depending on =3D=0Awhere the thetaPP started.=0A=0AMy reply t= o his reply: =A0I made the assumption that the timing was originally "corre= ct" with the peak pressure occurring at the right time - not always a valid= assumption. =A0If the burn rate is slowed, the peak cylinder pressure will= occur at a later point in the cycle, reducing the power, but only if it wa= s originally correct.=A0=0A=0AI said:=0AFurther, when the mixture is leaned= past the best power (or maybe peak =3D=0AEGT) the flame travel is even slo= wer and consequently the exhaust =3D=0Atemperature will likely just continu= e to go up when leaning, not peak =3D=0Aand go down.=0A=0AWalter replied:= =0ANO!=A0 EGT will always rise to peak, then fall when LOP.=A0 ALWAYS.=A0 U= nless, =3D=0Aof course, Sir Isaac Newton was wrong.=0A=0A=0AMy reply to his= reply: =A0I'm not sure Walter conclusion is always correct, especially whe= n running on one plug(which was how the conversation started) and at low BM= EP (naturally aspirated at high altitude. =A0I have tested my Lycoming at 1= 5,000 feet (both plugs firing) and found that, while there was a noticeable= change in slope of the EGT when going LOP, with the slope leveled off and = then continued to go up, not down. =A0In another case I was completing a fl= ight with the Lightspeed not firing on all cylinders. =A0The only way I cou= ld keep the EGT down to a reasonable value was to run ROP - when going lean= the EGT of that cylinder would seem to just keep rising as I leaned. =A0My= conclusion is that the EGT doesn't ALWAYS decrease LOP. =A0If the flame tr= avel is already slow with the thetaPP occurring after the optimum, the oppo= site can happen. =A0 I'd challenge Walter to do a quick dyno test at maybe = 15 inches MAP with only one plug firing. =A0What does the EGT vs fuel flow curve look like?=0A=0AGary=0A=0Aps: =A0There was another post= that concerned itself about doing a mag test in flight. =A0It suggested it= be done at only certain conditions. =A0Actually a single mag should fire t= he mixture reliably under ALL conditions. =A0Otherwise there is something w= rong. =A0I agree with the idea of doing inflight mag checks, but I'll admit= I have a fundamental problem shutting things off in flight, so I rarely do= them. =A0It makes all the sense in the world to do a quick mag check after= flight. =A0What better time to find out if maintenance is required?=A0 ---96787742-1451441967-1382608937=:90376 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
It is with great reluctance that I would contradict - or= even question - anything said by Walter, but here goes...


I said:

The slower burn rate on = one plug means that a significant portion of the =3D
burn happens during the expansion stroke and less heat is converted to = =3D
power. =3D20

Walter replied:
Uh, not really.  You can= actually end up with MORE power, depending on =3D
where the thetaPP started.

My reply to hi= s reply:  I made the assumption that the timing was originally "correc= t" with the peak pressure occurring at the right time - not always a valid = assumption.  If the burn rate is slowed, the peak cylinder pressure wi= ll occur at a later point in the cycle, reducing the power, but only if it = was originally correct. 
=
I said:
Fur= ther, when the mixture is leaned past the best power (or maybe peak =3D
EGT) the flame travel is even slower and cons= equently the exhaust =3D
temperature will likely j= ust continue to go up when leaning, not peak =3D
a= nd go down.

Walter replied:<= br style=3D"font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'L= ucida Grande', sans-serif; font-size: 13px;">NO!  EGT will always rise to peak, then fall when LO= P.  ALWAYS.  Unless, =3D
of course, Sir = Isaac Newton was wrong.

My reply to his rep= ly:  I'm not sure Walter conclusion is always correct, especially when= running on one plug(which was how the conversation started) and at low BME= P (naturally aspirated at high altitude.  I have tested my Lycoming at= 15,000 feet (both plugs firing) and found that, while there was a noticeab= le change in slope of the EGT when going LOP, with the slope leveled off an= d then continued to go up, not down.  In another case I was completing a flight with the Lightspeed not firing on all cylinders.  = ;The only way I could keep the EGT down to a reasonable value was to run RO= P - when going lean the EGT of that cylinder would seem to just keep rising= as I leaned.  My conclusion is that the EGT doesn't ALWAYS decrease L= OP.  If the flame travel is already slow with the thetaPP occurring af= ter the optimum, the opposite can happen.   I'd challenge Walter to do= a quick dyno test at maybe 15 inches MAP with only one plug firing.  = What does the EGT vs fuel flow curve look like?
Gary
<= br>
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