Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Sun, 03 Apr 2005 17:29:46 -0400 Message-ID: X-Original-Return-Path: Received: from sccrmhc13.comcast.net ([204.127.202.64] verified) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 853603 for lml@lancaironline.net; Sun, 03 Apr 2005 17:05:10 -0400 Received-SPF: none receiver=logan.com; client-ip=204.127.202.64; envelope-from=mjrav@comcast.net Received: from mark1 (c-65-96-140-242.hsd1.ma.comcast.net[65.96.140.242]) by comcast.net (sccrmhc13) with SMTP id <2005040321042101600rte80e>; Sun, 3 Apr 2005 21:04:21 +0000 X-Original-Message-ID: <004201c53891$5d2b0140$f28c6041@mark1> From: "Mark Ravinski" X-Original-To: "Lancair Mailing List" Subject: Oil and Warming up X-Original-Date: Sun, 3 Apr 2005 17:09:02 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003F_01C5386F.D5BF3350" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1478 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1478 This is a multi-part message in MIME format. ------=_NextPart_000_003F_01C5386F.D5BF3350 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Walter, Gary, First let me thank you for all the great posts that I've found so = informative over the years. And thank you Marv. The benefits can't be overstated. Some of the reasoning behind my choice of warming up comes from the = information available concerning starting a cold engine. Here in the northeast, preheating is many times required. ( I use 32 = deg F as a guide but others differ. ) Without this preheat, cylinder walls can be scored because the aluminum = piston will expand more and faster than the steel cylinders, which are = distorting under the stress of the rapid heating. Clearances are = reduced not allowing enough oil for the rings or even binding the = pistons. This scenario is obviously worse for a tight engine. Walter, your concerns on keeping the CHT's cooler seem to be more of a = summer operations concern. I couldn't agree more and do rush to the end = of the runway in warm weather. Temp is always at least 100f. Your = reference to Lycoming's position on this eludes me. My Lycoming = Operators Manual specifically calls for a "warm up" as part of the = ground check and has instructions for doing so. However, no temperature = information is given other than in "operating conditions" where there is = a note not to run below 140F for continuous operation. Gary, The cooling effects of the oil are more limited with less flow. = There is a squirt tube that directs an oil on the bottom of each piston = and excess flow to the valve mechanism helps cool the cylinder heads. I = know the oil carries a fair portion of the cooling load but have no = data or numbers. As an engineer, I'm assuming that the faster the cylinders are heated = the more internal stress occurs. (Which leads to cracks) Most of us aren't looking at the CHT's during to first part of takeoff = roll but I know the temps are climbing really fast. I'll bet some data might be provided by anyone with a data recorder ( = Like Greyhawk for instance) who could quantify the rate of change of = CHT's on takeoff as opposed to other phases of flight. My bet is that = it's the fastest changing part of the flight. I've chosen 100F as a reasonable starting point. The warmer the engine = is before full power is added the slower will be the rate of change. If anyone can show me how to do it better, I'd appreciate it. What temperature would you hang your hat on Walter - as ideal? Mark Ravinski N360KB 1320 hrs If you have any data to support that contention, I would really = appreciate seeing it. I know of no such data and do not share your = concern. As a matter of fact, waiting until the cylinders are a higher = temperature before takeoff, only serves to end up with a hotter CHT = during initial climb. I'd rather keep the cylinders cool. TCM, Lycoming, = Pratt & Whitney, and Wright all seem to agree with that. I think they're = right. Walter ------=_NextPart_000_003F_01C5386F.D5BF3350 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Walter,   =  Gary,
 
First let me thank you for all the = great posts that=20 I've found so informative over the years.
And thank you Marv.  The benefits = can't be=20 overstated.
 
Some of the reasoning behind my choice = of warming=20 up comes from the information available concerning starting a cold=20 engine.
Here in the northeast, preheating is = many times=20 required.  ( I use 32 deg F as a guide but others differ. = )
Without this preheat, cylinder walls = can be scored=20 because the aluminum piston will expand more and faster than the steel=20 cylinders, which are distorting under the stress of the rapid = heating. =20 Clearances are reduced not allowing enough oil for the rings or even = binding the=20 pistons.
This scenario is obviously worse for a = tight=20 engine.
 
Walter, your concerns on keeping the = CHT's cooler=20 seem to be more of a summer operations concern.  I couldn't agree = more and=20 do rush to the end of the runway in warm weather.  Temp is always = at least=20 100f.  Your reference to Lycoming's position on this eludes = me.  My=20 Lycoming Operators Manual specifically calls for a "warm up" as part of = the=20 ground check and has instructions for doing so.  However, no = temperature=20 information is given other than in "operating conditions" where there is = a note=20 not to run below 140F for continuous operation.
 
Gary,  The cooling effects of the = oil are more=20 limited with less flow.  There is a squirt tube that directs an oil = on the=20 bottom of each piston and excess flow to the valve mechanism helps cool = the=20 cylinder heads.  I know  the oil carries a fair portion = of the=20 cooling load but have no data or numbers.
 
As an engineer, I'm assuming that the = faster the=20 cylinders are heated the more internal stress occurs.  (Which leads = to=20 cracks)
Most of us aren't looking at the CHT's = during to=20 first part of takeoff roll but I know the temps are climbing really=20 fast.
I'll bet some data might be provided by = anyone with=20 a data recorder ( Like Greyhawk for instance) who could quantify = the rate=20 of change of CHT's on takeoff as opposed to other phases of = flight.  My bet=20 is that it's the fastest changing part of the flight.
I've chosen 100F as a reasonable = starting=20 point.  The warmer the engine is before full power is added the = slower will=20 be the rate of change.
If anyone can show me how to do it = better, I'd=20 appreciate it.
What temperature would you hang your = hat on Walter=20 - as ideal?
 
Mark Ravinski
N360KB 1320 hrs

 
 
If you have any data to = support that=20 contention, I would really appreciate seeing it. I know of no such data = and do=20 not share your concern. As a matter of fact, waiting until the cylinders = are a=20 higher temperature before takeoff, only serves to end up with a hotter = CHT=20 during initial climb. I'd rather keep the cylinders cool. TCM, Lycoming, = Pratt=20 & Whitney, and Wright all seem to agree with that. I think they're=20 right.

Walter
 
 
 
 
------=_NextPart_000_003F_01C5386F.D5BF3350--