X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 02 Jun 2007 16:46:20 -0400 Message-ID: X-Original-Return-Path: Received: from smtp113.sbc.mail.mud.yahoo.com ([68.142.198.212] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with SMTP id 2080709 for lml@lancaironline.net; Sat, 02 Jun 2007 16:08:17 -0400 Received-SPF: none receiver=logan.com; client-ip=68.142.198.212; envelope-from=elippse@sbcglobal.net Received: (qmail 87485 invoked from network); 2 Jun 2007 20:07:40 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=sbcglobal.net; h=Received:X-YMail-OSG:Message-ID:From:To:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=GqMoHL72BxmqERPkvcTXNWPO9g/pWUMvtfmlTpDyQNjZBnGQOSja9GBcyg6c/idPs30yCv+xoFatsUXM+7Tua6RyjOOEwF59Q5tSCyeshuKW5vCbMD9iz94LoYIZi2ROfmPi1H8UP/7kIVvj58mOMb7OfIfuT/1Dluy5GC17B+g= ; Received: from unknown (HELO Computerroom) (elippse@sbcglobal.net@75.15.147.156 with login) by smtp113.sbc.mail.mud.yahoo.com with SMTP; 2 Jun 2007 20:07:39 -0000 X-YMail-OSG: KzxeINUVM1nlJDzvC7vGvT8OtnVkR4V.k4mZIODq3vPG2niTMaCa1oIpQ0npUKnl2gIcUOxp8YmmYwrEalaSQNUGSG9RWE1J5Snf8EkzCsF1KSo7jQg- X-Original-Message-ID: <000801c7a551$aeaf3340$9c930f4b@Computerroom> From: "Paul Lipps" X-Original-To: "Marv Kaye" Subject: Detonation & pre-ignition X-Original-Date: Sat, 2 Jun 2007 13:07:42 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0005_01C7A517.00E113D0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 This is a multi-part message in MIME format. ------=_NextPart_000_0005_01C7A517.00E113D0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable I'm having a little problem here in how the words "detonation" and = "pre-ignition" are sometimes used. I am of the understanding that = detonation refers to a spark-triggered event in which the air-fuel had a = more-than-even or explosive combustion take place resulting in the = "ping" we hear in our cars. Pre-ignition, as the name implies, is where = combustion is triggered by some source earlier than the normal spark = event. As I have read, "detonation can cause mechanical damage such as = broken ring lands, abrasive pitting of the piston crown, and = overheating.* "Detonation is not necessarily destructive"*, and "An = engine that is making O.5 HP/in^3 or less can sustain moderate levels of = of detonation without any damage; but an engine that is making = 1.5HP/in^3, if it detonates, it will probably be damaged fairly = quickly...within minutes."* "Detonation will actually cause EGTs to = drop."* "...most engines will live with a fairly high level of = detonation for some period of time. It is not an instantaneous type of = failure."* "There are no engines that will live for any period of time when = pre-ignition occurs. When people see broken ring lands they mistakenly = blame it on on pre-ignition and overlook the hammering from detonation = that caused the problem. A hole in the middle of the piston, = particularly a melted hole in the middle of the piston, is due to the = extreme heat and pressure of pre-ignition."* "...the most likely point = for pre-ignition to occur is 180 BTDC, some 160 degrees before the spark = plug would have fired because that's the point (if there is a glowing = ember in the chamber) when it's most likely ignited. We are talking some = 160-180 degrees of burn being compressed that would normally be = relatively cool. A piston will only take a few revolutions of that = distress before it fails. As for detonation, it can get hammered-on for = seconds, minutes, or hours depending on the output of the engine and = load, before any damage occurs. Pre-ignition damage is almost = instantaneous."*=20 *These quotes are taken from an article by GM Staff Engineer Allen W. = Cline appearing in Contact! magazine issue #54. Those who would care to = read the whole article with much more on the subject than what I have = conveyed here should go to www.contactmagazine.com and order reprints = of this issue. ------=_NextPart_000_0005_01C7A517.00E113D0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
I'm having a little problem here in how the = words=20 "detonation" and "pre-ignition" are sometimes used. I am of the = understanding=20 that detonation refers to a spark-triggered event in which the air-fuel = had a=20 more-than-even or explosive combustion take place resulting in the = "ping"=20 we hear in our cars. Pre-ignition, as the name implies, is where = combustion is=20 triggered by some source earlier than the normal spark event. As I have = read,=20 "detonation can cause mechanical damage such as broken ring lands, = abrasive=20 pitting of the piston crown, and overheating.* "Detonation is not = necessarily=20 destructive"*, and "An engine that is making O.5 HP/in^3 or less can = sustain=20 moderate levels of of detonation without any damage; but an engine that = is=20 making 1.5HP/in^3, if it detonates, it will probably be damaged fairly=20 quickly...within minutes."* "Detonation will actually cause EGTs to = drop."*=20 "...most engines will live with a fairly high level of detonation for = some=20 period of time. It is not an instantaneous type of = failure."*
"There are no engines that will live for any = period of=20 time when pre-ignition occurs. When people see broken ring lands they = mistakenly=20 blame it on on pre-ignition and overlook the hammering from detonation = that=20 caused the problem. A hole in the middle of the piston, particularly a = melted=20 hole in the middle of the piston, is due to the extreme heat and = pressure of=20 pre-ignition."* "...the most likely point for pre-ignition to occur is = 180 BTDC,=20 some 160 degrees before the spark plug would have fired because that's = the point=20 (if there is a glowing ember in the chamber) when it's most likely = ignited. We=20 are talking some 160-180 degrees of burn being compressed that would = normally be=20 relatively cool. A piston will only take a few revolutions of that = distress=20 before it fails. As for detonation, it can get hammered-on for seconds, = minutes,=20 or hours depending on the output of the engine and load, before any = damage=20 occurs. Pre-ignition damage is almost instantaneous."*
*These quotes are taken from an article = by GM Staff=20 Engineer Allen W. Cline appearing in Contact! magazine issue = #54. Those who=20 would care to read the whole article with much more on the subject than = what I=20 have conveyed here should go to www.contactmagazine.com = and=20 order reprints of this issue.
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