Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Sun, 28 Mar 2004 15:32:44 -0500 Message-ID: X-Original-Return-Path: Received: from [68.89.254.181] (HELO sdf1.mail.taturbo.com) by logan.com (CommuniGate Pro SMTP 4.2b1) with ESMTP id 3131594 for lml@lancaironline.net; Sun, 28 Mar 2004 14:34:18 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C414FB.D1414DE2" Subject: RE: [LML] Reply to Reply on "lower EGT temps" content-class: urn:content-classes:message X-MimeOLE: Produced By Microsoft Exchange V6.0.6487.1 X-Original-Date: Sun, 28 Mar 2004 13:35:25 -0600 X-Original-Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [LML] Reply to Reply on "lower EGT temps" Thread-Index: AcQU1CgzuWxu0rifRV6Y1XMKvYIB9wAJBTOg From: "George Braly" X-Original-To: "Lancair Mailing List" This is a multi-part message in MIME format. ------_=_NextPart_001_01C414FB.D1414DE2 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable =20 =20 Scott, let me take the most important part (your footnote) of your = response to Walter, first: =20 =20 =20 >>PS: BTW, For my Lyc I/O 320, electronic spark advance does not occur = above 26" MAP (generally below 4500-5000 Palt), and then gingerly so = thereafter with little power effect, even with the reduced fuel flows. = For my case this is yet awaiting further study. Still, above 26" I see = reduced EGTs. =20 PPS: How accurate should the timing be? + or - 2 degrees? + or - ? = degrees?<< =20 =20 If your LASAR system does NOT change the timing from stock above 26" MAP = - - (ie, full or near full power) - - AND - - you are seeing lower = EGTs, : =20 THEN - - There is ONLY one explanation that is consistent with all = of the data that I have seen. The EFFECTIVE timing, as measured by = the location of the peak of combustion pressure after TDC *IS* changing = significantly. =20 The change in the location of the peak of the combustion event will be = measured closer to TDC and the peak pressures observed will be = substantially higher than the OEM intended them to be when they set the = original stock timing on the magnetos. =20 Notice... I said the "effective" timing. The effective timing = includes all aspects of the spark issue involved in initiating = combustion, including "better" sparks through higher technology, as = well as "when" the sparks actually fire measured in relation to TDC =20 Frankly, at high power and rpm, properly maintained magnetos do a = pretty good job in terms of the "quality" of the spark, and most = electronic ignition systems don't do much better in terms of the quality = of the spark. =20 =20 =20 ********************************* =20 As to the other issues you raise: =20 >> Pleeeeeeease. I know that the sky is falling and my engine is = headed for doomsday 'cause I haven't been to an advanced pilot seminar - = but, at least try to help us understand why our observations, experience = and understanding of ignition events at altitude are not just the = product of hypoxia induced lightheadedness. << =20 Ok, Scott, Walter was a little cryptic. =20 =20 Let me try to be a bit more elaborate: =20 =20 >> 1. You mean the PRISM system doesn't use modern electronic ignition = components and controls, including timing? << =20 =20 I am a bit confused by this comment, and I don't know what the = reference was to this. =20 =20 The issue is NOT how the spark is generated - - it can be a big box of = quick matches set off by Santa's little helpers, for all I care - - = but the issue is what is the effect of the nature and timing of the = event that initiates combustion on the resulting important stuff that = happens in the combustion chamber after the combustion event is started. =20 =20 >> 2. Do you mean that fixed timing, developed via compromise, is the = best for all operating conditions? << =20 =20 No. But that doesn't mean that electronic timing & sparks - - done = without the benefit of extremely thorough understandings of the = combustion events is going to make it better - - without creating other = problems - - either. However, it is remarkable how the combination = of the right fuel flow (which greatly influences the "effective" timing) = and fixed timing magnetos can do a fairly effective job. =20 >> 3. Do you mean that the spark energy, shape, duration and = consistency is of the same quality for electronic ignitions and = magnetos? << =20 No. In some cases, it is worse for electronic ignitions !! =20 =20 But, properly done, electronic ignitions can improve on the important = aspects of the initiating sparks that start the combustion events. It = just requires that the electronic stuff be originally designed with a = really thorough understanding of what is important about the combustion = events. From what I have observed, this is not always the case. =20 =20 >> 4. Are you telling me that our excess fuel delivery systems are so = good that no combustion is occurring in the exhaust pipe near the EGT = probe? << =20 No. Not sure how that plays into this discussion. Later effective = combustion ignition events will result in higher EGTs. Earlier = effective combustion ignition events will result in lower EGTS, = assuming nobody has changed the camshaft in the mean time! =20 =20 >> 5. Do you mean that magnetos deliver a consistent spark (time, = duration and strength) 100% of the time when one manufacturer states = that there can be magneto spark impairments of up to 10% of the time? = And, that this deficient combustion in the cylinder might lead to some = combustion completion in the pipe? << =20 =20 No. However, consider, the following: I have logged the details = (as in 0.1 to 0.4 degree crank resolution) of the spark and combustion = events over several thousands of combustion events over several years, = and studied them - - manually. I have developed software that can = study them automatically, and summarize the results with coefficients of = variability for almost every conceivable spark and resulting combustion = event parameter. And we have done this for millions of spark events. =20 We have done this for both magnetos and electronic ignitions. There is = some variability in the magneto spark events and the electronic spark = events. However, on properly maintained magnetos, it does not result = in anything like the kinds of changes in EGTs that you are reporting. = =20 =20 Regards, George=20 =20 =20 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.595 / Virus Database: 378 - Release Date: 2/25/2004 =20 ------_=_NextPart_001_01C414FB.D1414DE2 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
 
Scott,  let me take the most = important=20 part (your footnote) of your response to Walter, first:  =
 
 
>>PS: BTW, For my Lyc = I/O 320,=20 electronic spark advance does not occur above 26" MAP (generally below = 4500-5000=20 Palt), and then gingerly so thereafter with little power effect, even = with the=20 reduced fuel flows.  For my case this is yet awaiting further=20 study.  Still, above 26" I see reduced EGTs.
 
PPS: How accurate should the timing be? + or - 2 degrees? + or - ?=20 degrees?<<
 
 
If your LASAR system does NOT = change the=20 timing from stock above 26" MAP - - (ie, full or near full power)  = -=20 -  AND - -  you are seeing lower EGTs, :
 
    THEN  = - -=20  There is ONLY one explanation that is consistent with all of the = data that=20 I have seen.   The EFFECTIVE timing, as measured by  the = location=20 of the peak of combustion pressure after TDC  *IS* changing=20 significantly.
 
The change in the location of = the peak=20 of the combustion event will be measured closer to TDC and the peak = pressures=20 observed will be substantially higher than the OEM intended them to be = when they=20 set the original stock timing on the magnetos.
 
    Notice... I = said the=20 "effective" timing.   The effective timing includes all = aspects of the=20 spark issue involved in initiating combustion,  including = "better" =20 sparks through higher technology, as well as "when" the sparks actually = fire=20 measured in relation to  TDC
 
 Frankly,  at high power = and rpm,=20 properly maintained magnetos do a pretty good job in terms of the=20 "quality"  of the spark,  and most electronic ignition systems = don't=20 do much better in terms of the quality of the spark. 
 
 
*********************************
=
 
As to the other issues you=20 raise:
 
 >> Pleeeeeeease. = I know=20 that the sky is falling and my engine is headed for doomsday 'cause I = haven't=20 been to an advanced pilot seminar - but, at least try to help us = understand why=20 our observations, experience and understanding of ignition events at = altitude=20 are not just the product of hypoxia induced lightheadedness. <<
 
Ok, Scott,  Walter was a = little=20 cryptic.  
 
Let me try to be a bit more=20 elaborate:
 
 
 >> 1. You=20 mean the PRISM system doesn't use modern electronic ignition = components=20 and controls, including timing? <<  
 
I am a bit confused by this = comment, =20 and I don't know what the reference was to = this.  
 
The issue is NOT how the spark = is=20 generated - -  it can be a big box of quick matches set off = by=20 Santa's little helpers,  for all I care - -  but the = issue is=20 what is the effect of the nature and timing of the event that = initiates=20 combustion on the resulting important stuff that happens in the = combustion=20 chamber after the combustion event is started.
 
 
 >> 2. Do = you mean=20 that fixed timing, developed via compromise, is the best for all = operating=20 conditions? <<  
 
No.  But that doesn't mean = that=20 electronic timing & sparks - -  done without the benefit of = extremely=20 thorough understandings of the combustion events is going to make = it=20 better - - without creating other problems - - = either.   =20 However,  it is remarkable how the combination of the right fuel = flow=20 (which greatly influences the "effective" timing) and fixed timing = magnetos=20 can do a fairly effective job.
 
 >> 3. Do = you mean=20 that the spark energy, shape, duration and consistency is of the same=20 quality for electronic ignitions and magnetos?   <<
 
No.  In some cases, it = is worse=20 for electronic ignitions !!   
 
But,  properly done, = electronic=20 ignitions can improve on the important aspects of the initiating = sparks that=20 start the combustion events.   It just requires that the = electronic=20 stuff be originally designed with a really thorough understanding = of what=20 is important about the combustion events.   From what I = have=20 observed,  this is not always the case. 
 
 >> 4. = Are you=20 telling me that our excess fuel delivery systems are so good that no=20 combustion is occurring in the exhaust pipe near the EGT probe? <<
 
No.  Not sure how that = plays into=20 this discussion.   Later effective combustion ignition=20 events will result in higher EGTs.  Earlier effective = combustion=20 ignition events will result in lower EGTS,  assuming nobody has = changed=20 the camshaft in the mean time!  <g>
 
 
 >> 5. Do = you mean=20 that magnetos deliver a consistent spark (time, duration and strength) = 100% of=20 the time when one manufacturer states that there can be magneto = spark=20 impairments of up to 10% of the time? And, that = this deficient=20 combustion in the cylinder might lead to some combustion completion in = the=20 pipe? =20 <<   
 
No.    = However, =20 consider, the following:   I have  logged the = details=20 (as in  0.1 to 0.4 degree crank resolution) of the spark and = combustion=20 events over  several thousands of combustion events over several = years,=20 and studied them - - manually.   I have developed software = that=20 can  study them automatically, and summarize the results = with=20 coefficients of variability for almost every conceivable spark and = resulting=20 combustion event parameter.  And we have done this for millions = of spark=20 events.
 
We have done this for both = magnetos=20 and electronic ignitions.   There is some variability in the = magneto=20 spark events and the electronic spark events.  =20 However,  on properly maintained magnetos,  it = does not=20 result in  anything like the kinds of changes in EGTs that = you are=20 reporting.    
 
Regards,  George =
 
 

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