X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 26 Nov 2011 10:22:55 -0500 Message-ID: X-Original-Return-Path: Received: from nm18.bullet.mail.ac4.yahoo.com ([98.139.52.215] verified) by logan.com (CommuniGate Pro SMTP 5.4.2) with SMTP id 5214541 for lml@lancaironline.net; Fri, 25 Nov 2011 23:34:17 -0500 Received-SPF: none receiver=logan.com; client-ip=98.139.52.215; envelope-from=chris_zavatson@yahoo.com Received: from [98.139.52.194] by nm18.bullet.mail.ac4.yahoo.com with NNFMP; 26 Nov 2011 04:33:42 -0000 Received: from [98.139.52.146] by tm7.bullet.mail.ac4.yahoo.com with NNFMP; 26 Nov 2011 04:33:42 -0000 Received: from [127.0.0.1] by omp1029.mail.ac4.yahoo.com with NNFMP; 26 Nov 2011 04:33:42 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 506415.74848.bm@omp1029.mail.ac4.yahoo.com Received: (qmail 7704 invoked by uid 60001); 26 Nov 2011 04:33:42 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=Csftvsubosew5nWYRoFF4meVRHCD1UFf2ca4bNmrZpWs3hLO2AjcLE7S83DYWFhiKDNgY8oiId9IxV7h2TNdV0ddwMC4pPPi4KxDcsScnwgRf4710w1Pl8qhLvq1M2995g92ZXSaDPiKUkHIv21RHFTES5JAXAFHTgMW4ViKWlg=; X-YMail-OSG: bJrzfSAVM1nh.5RTH3YnIckfEvDlhr2gm2WN6heXITd2iqX lLrfXcJr596KoF_1V2RMEAsWDz118SRwZZ0u9x3gWHIj0qudbcZvWTol4OCk e3hyHlqURsHgZNP0Iev2InCBTquavLq2mILcMBA4zgSrHvo8dTDyN0ec5gZ8 6aVKRGrzVzNsJ9LF_R.a6i3SpFW19MMwQ71wCOzcas.WsatDwEykzHTWlIoY RH9CsKx10QTbpFg3UgKtt3XJSc9eEIoCcVL82zrW1oOR3wqiK.YsGOvHlLbe sttJufxnaL_EjVZtBrHkR3MkxtR9Q4wnHXkaErHnD5fu3OVZBbqeBVdn7PfV 18eM8v80xB9RzC1JFjo87m4EpyVxQeJ0ze0djQxsBj_Bit7GTe9ydLs_DoxE Ha46nD98ZCqxadEw23_Fky9fn3rhH4a6NCrQLgQasfpDsnaHC8C4W23PY1qC ZJZdEE9uVejR3QdxYToXBg80aEt3_xbd.6.g- Received: from [99.137.192.233] by web36904.mail.mud.yahoo.com via HTTP; Fri, 25 Nov 2011 20:33:41 PST X-Mailer: YahooMailWebService/0.8.115.325013 References: X-Original-Message-ID: <1322282021.6056.YahooMailNeo@web36904.mail.mud.yahoo.com> X-Original-Date: Fri, 25 Nov 2011 20:33:41 -0800 (PST) From: Chris Zavatson Reply-To: Chris Zavatson Subject: Re: [LML] Re: E-Mag/P-Mag X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-2114655128-458376456-1322282021=:6056" ---2114655128-458376456-1322282021=:6056 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Gary,=0AThanks for all the detail.=0AChris=A0=0A=0AFrom: Gary Casey =0ATo: lml@lancaironline.net =0ASent: Friday, November 25, 2= 011 6:12 AM=0ASubject: [LML] Re: E-Mag/P-Mag=0A=0A=0AChris,=0AI wish I had = really hard numbers on the benefit.=A0 If you read some of the stuff from s= uppliers, you could get the idea that there is an "up to" 20 percent improv= ement at altitude.=A0 I don't think that the average user will see that muc= h, but the benefit is still substantial.=A0 The engine will produce most po= wer if the spark is adjusted so that the peak cylinder pressure occurs at a= bout 16 degrees after top center (ATC) and that is pretty much independent = of engine type and operating condition.=A0 The problem is that the flame sp= eed varies, depending on a number of parameters.=A0 Probably the only two t= hat are pertinent are manifold pressure and mixture.=A0 You might think tha= t engine speed is important (higher speed gives the flame less time to prop= agate), but the turbulence in the chamber increases as the engine speed inc= reases and that speeds up the flame travel enough or nearly enough to negat= e that effect.=0A=0AThe flame travels essentially by "jumping" from one "tr= eetop" of fuel to the next, so when the fuel molecules are further apart th= e flame travel is slower.=A0 That delays the point at which maximum cylinde= r pressure occurs.=A0 So naturally, lower manifold pressure results in slow= er flame speed and leads to the requirement for more spark advance.=A0 The = same is true for leaner mixtures as that increases the distance between fue= l molecules.=A0 Somewhat counter-intuitive is that the same thing happens w= ith richer-than-stoichiometric mixtures, but that's a different topic.=A0 T= he peak flame speed occurs at roughly stoichimetric mixtures, which turns o= ut to be about 50 degrees rich of peak.=A0 And the important thing is that = the flame travel will slow progressively faster and faster (does that make = sense?=A0 I hope so) as the mixture gets lean or the manifold pressure is r= educed.=A0 The reason is that after TDC the volume in the combustion chambe= r is increasing and that by itself slows the combustion (more distance between molecules).=A0 = So if the combustion doesn't come close to completion soon enough it will t= ake a long, long=A0time.=0A=0AThe common electronic ignition systems advanc= e the spark as a function of only manifold pressure - at least as far as I = know.=A0 At altitudes above 12,000 feet you can expect that the timing will= be several degrees advanced from that at sea level.=A0 That gives a certai= n benefit.=A0 I think the real improvement comes from running LOP at high a= ltitude.=A0 If you try to run LOP at very high altitude without the extra s= park advance the power output will drop faster than one might expect, essen= tially falling off the cliff.=A0 So yes, if you want to run at, say, 15,000= =A0AND LOP the extra spark advance could improve the efficiency of the engi= ne by maybe 20 percent.=A0 In this case I say "efficiency" as opposed to po= wer because the LOP operation will reduce the power output - the spark adva= nce will just keep it from reducing as much.=0A=0AIn theory, at least you c= ould then run at a fixed IAS at a higher altitude than you could otherwise = and reduce the fuel consumption by that 20 percent.=A0 But if you want to g= o as fast as possible at a given altitude you won't be running LOP and then= I suspect the improvement in speed at=A0that fixed altitude could be about= 2 percent.=0A=0AIt's not a simple subject, but I hope I've shed a little l= ight on it.=A0 How much improvement can you expect by running only one elec= tronic ignition?=A0 I've been told roughly half.=0A=0AGary Casey - sorry ab= out the long post.=0A=0AFrom chris:=0AGary,=0ACould you elaborate on the pe= rformance benefits to be expected from advanced spark at altitude. Efficien= cy, power, etc.=0A-just curious as I spend a lot of time between 13 and 18k= with my Slick mags and carb. and haven't really studied the topic.=0Athank= s, =0AChris Zavatson ---2114655128-458376456-1322282021=:6056 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Gary,
Thanks for all the d= etail.
Chris 

From:= Gary Casey <casey.gary@yahoo.com>
To: lml@lancaironline.net
Sent: Friday, November 25, 2011 6:12 AM
<= B>Subject: [LML] Re: E-Mag/P-M= ag

Chris,
I wish I had really hard numbers on the benefit.=   If you read some of the stuff from suppliers, you could get the idea= that there is an "up to" 20 percent improvement at altitude.  I don't= think that the average user will see that much, but the benefit is still s= ubstantial.  The engine will produce most power if the spark is adjust= ed so that the peak cylinder pressure occurs at about 16 degrees after top = center (ATC) and that is pretty much independent of engine type and operati= ng condition.  The problem is that the flame speed varies, depending o= n a number of parameters.  Probably the only two that are pertinent ar= e manifold pressure and mixture.  You might think that engine speed is= important (higher speed gives the flame less time to propagate), but the t= urbulence in the chamber increases as the engine speed increases and that s= peeds up the flame travel enough or nearly enough to negate that effect.
 
The flame travels essentially by "jumping" from one "treetop" of fuel = to the next, so when the fuel molecules are further apart the flame travel = is slower.  That delays the point at which maximum cylinder pressure o= ccurs.  So naturally, lower manifold pressure results in slower flame = speed and leads to the requirement for more spark advance.  The same i= s true for leaner mixtures as that increases the distance between fuel mole= cules.  Somewhat counter-intuitive is that the same thing happens with= richer-than-stoichiometric mixtures, but that's a different topic.  T= he peak flame speed occurs at roughly stoichimetric mixtures, which turns o= ut to be about 50 degrees rich of peak.  And the important thing is th= at the flame travel will slow progressively faster and faster (does that ma= ke sense?  I hope so) as the mixture gets lean or the manifold pressur= e is reduced.  The reason is that after TDC the volume in the combustion chamber is increasing and that by itself slows the combustion (= more distance between molecules).  So if the combustion doesn't come c= lose to completion soon enough it will take a long, long time.
 
The common electronic ignition systems advance the spark as a function= of only manifold pressure - at least as far as I know.  At altitudes = above 12,000 feet you can expect that the timing will be several degrees ad= vanced from that at sea level.  That gives a certain benefit.  I = think the real improvement comes from running LOP at high altitude.  I= f you try to run LOP at very high altitude without the extra spark advance = the power output will drop faster than one might expect, essentially fallin= g off the cliff.  So yes, if you want to run at, say, 15,000 AND = LOP the extra spark advance could improve the efficiency of the engine by m= aybe 20 percent.  In this case I say "efficiency" as opposed to power = because the LOP operation will reduce the power output - the spark advance = will just keep it from reducing as much.
 
In theory, at least you could then run at a fixed IAS at a higher alti= tude than you could otherwise and reduce the fuel consumption by that 20 pe= rcent.  But if you want to go as fast as possible at a given altitude = you won't be running LOP and then I suspect the improvement in speed at&nbs= p;that fixed altitude could be about 2 percent.
 
It's not a simple subject, but I hope I've shed a little light on it.&= nbsp; How much improvement can you expect by running only one electronic ig= nition?  I've been told roughly half.
 
Gary Casey - sorry about the long post.
 
From chris:
Gary,
Could you elaborat= e on the performance benefits to be expected from advanced spark at altitude. Efficiency, power, etc.=
-just curious as I spend a lot of time betwee= n 13 and 18k with my Slick mags and carb. and haven't really studied the topic.
thanks,
Chris Zavatson
 

<= BR>
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